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EP0634052A1 - Dispositifs et techniques optiques a semi-conducteur - Google Patents

Dispositifs et techniques optiques a semi-conducteur

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Publication number
EP0634052A1
EP0634052A1 EP93908605A EP93908605A EP0634052A1 EP 0634052 A1 EP0634052 A1 EP 0634052A1 EP 93908605 A EP93908605 A EP 93908605A EP 93908605 A EP93908605 A EP 93908605A EP 0634052 A1 EP0634052 A1 EP 0634052A1
Authority
EP
European Patent Office
Prior art keywords
semiconductor
laser
confining
aluminum
electrode elements
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93908605A
Other languages
German (de)
English (en)
Other versions
EP0634052A4 (fr
Inventor
Nick Holonyak, Jr.
Fred A. Kish
Stephen J. Caracci
Nada El-Zein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Illinois at Urbana Champaign
University of Illinois System
Original Assignee
University of Illinois at Urbana Champaign
University of Illinois System
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US07/860,454 external-priority patent/US5327448A/en
Priority claimed from US07/927,822 external-priority patent/US5353295A/en
Application filed by University of Illinois at Urbana Champaign, University of Illinois System filed Critical University of Illinois at Urbana Champaign
Publication of EP0634052A1 publication Critical patent/EP0634052A1/fr
Publication of EP0634052A4 publication Critical patent/EP0634052A4/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
    • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
    • H01L21/02172—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides
    • H01L21/02175—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal
    • H01L21/02178—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal the material containing aluminium, e.g. Al2O3
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
    • H01L21/02227—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process
    • H01L21/0223—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by oxidation, e.g. oxidation of the substrate
    • H01L21/02233—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by oxidation, e.g. oxidation of the substrate of the semiconductor substrate or a semiconductor layer
    • H01L21/02241—III-V semiconductor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
    • H01L21/02227—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process
    • H01L21/02255—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a process other than a deposition process formation by thermal treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1021—Coupled cavities
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1003—Waveguide having a modified shape along the axis, e.g. branched, curved, tapered, voids
    • H01S5/101—Curved waveguide
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1028—Coupling to elements in the cavity, e.g. coupling to waveguides adjacent the active region, e.g. forward coupled [DFC] structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1071—Ring-lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4031—Edge-emitting structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4031—Edge-emitting structures
    • H01S5/4056—Edge-emitting structures emitting light in more than one direction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4031—Edge-emitting structures
    • H01S5/4068—Edge-emitting structures with lateral coupling by axially offset or by merging waveguides, e.g. Y-couplers

Definitions

  • This invention relates to semiconductor devices and, more particularly, to techniques which employ a grown native oxide of aluminum to obtain improvements in III-V semiconductor lasers and waveguides, and also relates to semiconductor lasers which exhibit improved properties, including improved single mode operation, optical switching and bistability.
  • Ring lasers or “circular resonators” have also been proposed for applications such as filtering and multiplexing in so-called opto ⁇ electronic or integrated optical circuits. Fractions of a ring, such as a half-ring or a quarter-ring, with cleaved facets, have been used for various applications in optical communications.
  • index-guided arrays Another application where control of index of refraction is important is in coupled-stripe laser diode arrays. These arrays offer the possibility of obtaining high output powers with decreased beam divergence and single-longitudinal mode operation. Index-guided arrays, compared to their gain-guided counterparts, have advantages of increased mode stability and coherence, and decreased beam astigmatism.
  • IILD impurity induced layer disordering
  • Opto-electronic circuits in which devices in a semiconductor chip have interacting optical and electronic elements
  • circular or other curved optical signal paths are needed, particularly for the design and fabrication of relatively complex circuits. It is among the further objects of the present invention to provide an efficient semiconductor optical waveguide for use in opto-electronic semiconductor circuits.
  • the high gain required for oscillation in semiconductor lasers results in a large optical bandwidth in which laser operation is possible. This large bandwidth generally results in multiple-longitudinal-mode operation. For many applications, single-longitudinal-mode operation is required. Consequently, sophisticated structures such as the distributed feedback (DFB) laser [see D. R. Scifres, R. D. Burnham, and W. Streifer, Appl. Phys. Lett. 25, 203 (1974)] and the cleaved- coupled-cavity (C 3 ) laser [see W. T. Tsang, Lightwave Communications Technology, Part B, Semiconductor Injection Lasers, I, edited by W. T. Tsang, in Semiconductors and Semimetals, Vol. 22, edited by R.
  • DFB distributed feedback
  • C 3 cleaved- coupled-cavity
  • K. Willardson and A. C. Beer (Academic, Orlando, 1985), Chap. 5, pp. 257-373] have been developed to ensure single-mode operation.
  • the DFB laser employs a fine-scale periodic corrugation of relatively small index steps to interact with the electromagnetic wave.
  • the C 3 laser relies on several large-scale nonperiodic monolithic cavities for feedback and mode selection.
  • Optical switching and bistability are important for applications such as optical memories, optical signal processing, and optical logic elements.
  • a variety of semiconductor laser devices have exhibited switching and bistability, including: lasers with saturable absorbers [see M. I. Nathan, J. C. Marinace, R. F. Rutz, A. E. Michel, and G. J. Lasher, J. Appl. Phys. 36, 473 (1965); C. Harder, K. Y. Lau, and A. Yariv, IEEE J. Quantum Electron. QE-18, 1351 (1982); N. Yamada and J. S. Harris, Jr., Appl. Phys. Lett. 60, 2463 (1992)], ordinary tandem coupled-cavity lasers [see N. K. Dutta, G.
  • An aspect of the present invention is directed to improved techniques and devices employing, inter alia, an aluminum-bearing III-V semiconductor material and a native oxide of aluminum that is formed in the semiconductor material.
  • the technique comprises exposing an aluminum-bearing Group III-V semiconductor material to a water-containing environment and a temperature of at least about 375°C to convert at least a portion of the aluminum-bearing Group III-V semiconductor material to a native oxide.
  • the thickness of said native oxide formed thereby is substantially the same as or less than the thickness of that portion of said aluminum-bearing III-V semiconductor material converted into the native oxide.
  • the native oxide layer thus grown is denser and more stable than oxide layers formed from previous methods, meaning, for example, that they do not degrade under conditions of normal use and atmospheric exposure. Further, the native oxide was demonstrated to exhibit improved operating and performance characteristics,, for example with regard to metallization adherence and dielectric properties.
  • the native oxides were described as being useful in lasers, transistors, capacitors, waveguides and in other electrical and opto-electrical devices.
  • Anhydrous oxides of aluminum were noted to exhibit a relatively low index of refraction (less than about 2.0) and index of refraction can be used to distinguish the anhydrous oxide forms from the higher index hydrated oxide forms that are generally unsuitable for semiconductor applications due to properties such as expansion and instability.
  • a form of the invention is directed to a method of making a semiconductor laser having a light path that is at least partially curved, and comprises the following steps: forming a layered semiconductor structure comprising an active region between first and second semiconductor confining layers, the first and second semiconductor confining layers being of opposite conductivity types, and said first semiconductor confining layer being an aluminum-bearing III-V semiconductor material; applying a mask pattern over said first semiconductor confining layer, the pattern including a stripe that is at least partially curved; exposing unmasked portions of the first semiconductor confining layer to a water- containing environment and a temperature of at least 375 degrees C for a time sufficient to form a thick native oxide of aluminum in said first semiconductor confining layer; and coupling respective electrodes with said first and second semiconductor confining layers.
  • the active region includes at least a waveguide layer and a quantum well layer, and the respective electrodes are coupled to the semiconductor confining layers through further respective semiconductor layers.
  • the time of exposure may be selected to have said native oxide extend through at least most of the thickness of said first confining layer, and possibly through the entire thickness of said first confining layer.
  • Another form of the invention comprises a semiconductor passive optical waveguide, having a light path which is at least partially curved, that employs a thick native oxide of aluminum.
  • two linear arrays of end-coupled cavities (called minicavities) of a QWH semiconductor laser are defined by a native oxide of an aluminum-bearing III-V semiconductor material and are arranged side by side to obtain a two dimensional array, with resultant lateral coupling between the linear arrays.
  • the two dimensional array exhibits mode switching and multiple switching in the light power (L) versus current (I) characteristic (L-I) with increasing current.
  • a stripe laser is transversely coupled (or side-coupled) with a linear array of end-coupled minicavities. Bistability and switching are demonstrated in the light versus current (L-I) characteristic of a native-oxide-defined structure of this type.
  • the device with internally coupled elements and the current partitioned among the elements, exhibits a large hysteresis in the L-I curve, with switching from the stimulated to the spontaneous regime occurring over substantial power (light) and current ranges.
  • the linear array of "minilasers” and its resonance modulates and switches the stripe laser operation.
  • a semiconductor laser device includes first and second adjacent laser units formed on the same semiconductor substrate, each of the units including a laser cavity.
  • the laser cavity of the first unit has a substantially different longitudinal mode selection characteristic than the laser cavity of said second unit.
  • substantially different longitudinal mode section characteristics means that the first unit has a cavity mode spacing that is at least 10 percent greater that the cavity mode spacing of the second unit, and/or a primary emission wavelength that is at least 50 A greater than the primary emission wavelength of the second unit.
  • Means are provided for applying energizing signals to the first and second units to obtain laser emission from the units and lateral coupling between the cavities of the units.
  • a semiconductor laser device that includes a semiconductor active region disposed between first and second semiconductor confining layers.
  • An electrode array has electrode elements coupled with the first confining layer.
  • electrode elements is intended to include electrical contact regions (e.g. highly doped semiconductor regions) that contact an underlying semiconductor structure.
  • At least one opposing electrode is coupled with the second confining layer.
  • the electrode elements of the array are spaced apart and form a two-dimensional array that includes a plurality of electrode elements along a line and at least one further electrode element laterally spaced from the electrode element of said line.
  • Means are provided for applying electrical signals between the electrode elements and the at least one further electrode element and the opposing electrode to effect light emission in the active regions defined under the plurality electrode elements and at least one active region defined under the at least one further electrode element, and to effect lateral coupling of the emissions.
  • Fig. 1 is a scanning electron microscope image of a stained cross-section of a device in accordance with an embodiment of the invention.
  • Fig. 2 is a graph of cw light output (both ring ends) versus current for a device in accordance with an embodiment of the invention, and shows, in an inset, a surface photograph of the device.
  • Fig. 3 is a graph of pulsed light output (both ring ends) versus current for a device in accordance with an embodiment of the invention and shows, in the inset, single mode operation.
  • Fig. 4 shows near field image plots for the Fig. 3 device.
  • Fig. 5 is a graph of pulsed light output versus current for another device in accordance with the invention, the inset showing the device geometry.
  • Fig. 6 is a simplified cross-sectional representation of a semiconductor laser diode device in accordance with an embodiment of the invention.
  • Fig. 7 is a simplified cross-sectional diagram of another semiconductor laser device in accordance with a embodiment of the invention.
  • Fig. 8 is a simplified cross-sectional representation of a semiconductor optical waveguide in accordance with an embodiment of the invention.
  • Fig. 9 illustrates the surface configuration of a ring laser device.
  • Fig. 10 illustrates the surface configuration of a quarter-ring laser or waveguide.
  • Fig.s 11 and 12 illustrate the surface configuration of ring lasers or waveguides with different branch coupling arrangements.
  • Fig.s 13 and 14 illustrate the surface configuration of multi-stripe lasers or waveguides with ring coupling.
  • Fig. 15 illustrates the surface configuration of a series of coupled half-ring lasers or waveguides.
  • Fig. 16 illustrates the surface configuration of a multi- stripe laser or waveguide with half-ring coupling.
  • Fig. 17 illustrates the surface configuration of a curved laser or waveguide in which the light path becomes laterally offset.
  • Fig. 18 illustrates the surface configuration of a laser or waveguide which couples light in a single branch with four curved branches.
  • Fig. 19 shows continuous (cw) 300 K light output (single facet) versus current characteristic (L-I) of a native-oxide- defined two-dimensional (2-D) coupled-cavity Al ⁇ Ga l ⁇ As-GaAs QWH laser array (uncoated facets, ⁇ 300 ⁇ m total cavity length).
  • the threshold is 45 mA, and the power peaks at ⁇ 12.5 mW (115 mA) .
  • the inset shows a surface photomicrograph of the unmetallized 2-D twin linear array.
  • the rectangular minicavities are 4 ⁇ m wide, 19 ⁇ m long, and separated end-to- end by - 3 ⁇ m.
  • the two coupled linear arrays are separated by ⁇ 1 ⁇ m.
  • Fig. 20 shows longitudinal mode spectra (cw, 300 K) of the diode of Fig. 19 at (a) 115, (b) 150, and (c) 164 mA (points shown on the L-I of Fig. 5).
  • the single mode behavior at (a) 8280 A (115 mA) shifts to 8313 A at (b) 150 mA.
  • At (c) 164 mA single mode operation has switched off and the resonances of the 19 ⁇ m long minicavities are evident and marked with arrows.
  • the mode spacing is ⁇ 50 A, which agrees with the 19 ⁇ m minicavity length.
  • Fig. 21 shows the light output versus current characteristic (L-I, cw, 300 K) of a diode with the same geometry as that shown in Fig. 19.
  • the diode turns on and off twice as the current is increased.
  • the dashed line shows that the emission intensity in the valley region is in the range of spontaneous emission.
  • the inset shows single mode behavior (8340 A) persists to at least 415 mA ( ⁇ 81 ⁇ ), and is marked with a solid dot on the L-I curve.
  • Fig. 22 shows the near field (NF) emission patterns and longitudinal mode spectra of the diode of Fig. 21 near the diamond-shaped point at ⁇ 70 mA on the L-I characteristic.
  • the near field (NF) shows two intensity peaks of the twin linear array, with the width of 9.2 ⁇ m in accord with the geometry shown in Fig. 19.
  • the NF is twin lobed, with the device operating single mode (8260 A) but with also strong satellite longitudinal modes.
  • the NF emission from the right stripe disappears abruptly, with also an abrupt disappearance of the satellite longitudinal modes.
  • Fig. 23 shows the continuous 300 K light output (single facet, uncoated) versus current characteristic (L-I) of a native-oxide-defined Al ⁇ Ga l ⁇ As-GaAs single laser stripe side- coupled to a linear array of end-coupled minilasers.
  • the laser threshold is 32 mA, with abrupt switching from the stimulated (ON) to spontaneous (OFF) regime occurring at 168 mA.
  • the device exhibits bistability, switching back sharply from the spontaneous (OFF) to stimulated (ON) regime at 123 mA.
  • the diode geometry (prior to metallization) is shown in the inset and consists of a single ⁇ 6 ⁇ m-wide laser stripe side-coupled ( ⁇ 5 ⁇ m away) to a linear array of end-coupled minilasers (6 ⁇ m-wide, 19 ⁇ m long and 22 ⁇ m centers).
  • Fig. 24 shows the continuous 300 K light output (single facet, uncoated) versus current characteristic (L-I) of a device of the form of Fig. 23 (inset).
  • the laser exhibits a threshold of 27 mA, with switching and bistability occurring in the range 96-100 mA.
  • the device output consists essentially of a ⁇ 5.5 ⁇ m Gaussian near-field (NF) pattern from the single continuous stripe of Fig. 23.
  • the NF pattern is shown just before switching at (a) 99 mA (inset). After switching at (b) 100 mA, essentially no output is observed; on a higher sensitivity scale (b'), however, the same NF pattern is revealed.
  • Fig. 25 shows longitudinal mode spectra (cw, 300 K) of the diode of Fig. 24 corresponding to single mode stimulated emission (ON) at (a) and switched OFF to spontaneous emission at (b) .
  • Single mode laser operation is observed from threshold ( ⁇ 27 mA) to (a) ⁇ 99 mA, with output at large amplitude from only the continuous stripe of the diode (left stripe in Fig. 23 inset) .
  • the spontaneous emission OFF regime (b) the lower energy group of modes corresponds to the laser stripe and the higher energy group of modes to the linear array (see inset of Fig. 23).
  • Fig. 26 is diagram of a portion of the top surface of the device described in conjunction with Figures 23-25.
  • Fig. 27 is a cross-sectional diagram (not to scale), as taken through a section of the Fig. 26 device defined by arrows 13-13.
  • Fig. 28 is a cross-sectional diagram (not to scale), as taken through a section of the Fig. 26 device defined by arrows 14-14.
  • Fig. 29 is a cross-sectional diagram (not to scale), as taken through a section of the Fig. 26 device defined by arrows 15-15.
  • Fig. 30 illustrates a two-dimensional array that can be operated using two, three, or four terminals.
  • Fig. 31 illustrates a two-dimensional array with terminal control in both dimensions.
  • Figures 32-35 show plan views of ring lasers including minicavities in curved configurations in accordance with embodiments of the invention.
  • Figures 36-39 show plan views of adjacent ring and straight line lasers, with transverse coupling between laser cavities, and including configurations where the ring, the straight line, or both, are divided into minicavities.
  • Fig. 40 is a cross-sectional diagram (not to scale) of a vertical cavity laser device with transverse coupling between adjacent laser cavities having different mode selection characteristics.
  • Fig. 41 illustrates a two-dimensional array of vertical cavity laser units of the type illustrated in Fig. 40. DETAILED DESCRIPTION
  • a quantum well heterostructure is grown by metal-organic chemical vapor deposition ["MOCVD" - see for example, R.D. Dupuis et al.. Proceedings of The International Symposium on GaAs and Related Compounds, pp. 1- 9, Institute of Physics, London, 1979, and M.J. Ludowise, J. Appl. Phys., 58, R31, 1985] on an n-type GaAs substrate.
  • MOCVD metal-organic chemical vapor deposition
  • the confining layers are also sometimes called cladding layers.
  • the active region of the quantum well heterostructure is then grown, and includes symmetrical A1 Q 25 Ga 075 As waveguide layers, undoped and of thickness about 750 A each, on either side of a GaAs quantum well of thickness about 100 A.
  • An upper confining (or cladding) layer of p-type Al 08 Ga Q 2 As is grown to a thickness of about 0.6 ⁇ m, and a heavily doped p-type GaAs contact layer is grown thereon, the contact layer having a thickness of about 800 A.
  • fabrication of a laser begins with the patterning of about 1000 A of Si 3 N 4 into rings [25- ⁇ m wide annulus, 250 ⁇ m inside diameter (ID), 300 ⁇ m outside diameter (OD)].
  • the Si 3 N 4 rings serve as a mask for the chemical etching (H 2 S0 4 :H 2 0 2 :H 2 0, 1:8:80) of the contact layer, thus leaving the Al ⁇ Ga l ⁇ As upper confining layer exposed inside and outside of the masked rings.
  • the sample is then placed in an open tube furnace, supplied with H 2 0 vapor and N 2 , at 450°C for 35 minutes.
  • This process results in the conversion of the upper confining layer (where exposed) to a native oxide having an index of refraction of about 1.6.
  • the oxide extends downward through the entire upper confining layer as shown in Fig. 1 by the scanning electron microscope (SEM) image of a stained cross section.
  • SEM scanning electron microscope
  • the oxide is deeper at the ring edge than beyond (to the right in Fig. 1). This effect may be a result of changes in H 2 0 adsorption, O/H diffusion, or stress induced by the presence of the masking stripe.
  • the oxide profile is fairly isotropic, however, extending laterally essentially to the same extent as it does in depth.
  • TEM images of similarly oxidized crystals indicate that some oxidation (about 200 A) of the underlying A1 Q 23 Ga 077 As waveguide region occurs.
  • the low-index native oxide extends into the waveguide layer, creating large lateral index steps for sidewise optical confinement and waveguiding.
  • Calculations based on propagation in a 4-layer slab waveguide [see G.E. Smith, IEEE J. Quantum Electron., QE-4, 288 (1968)] for this deep oxide edge indicate an effective lateral index step greater than 0.05.
  • structures with the native oxide located about 1000 A vertically away from the waveguide result in an insufficient index step for ring oscillation.
  • effective lasers can be made with lateral native oxide that extends only partially through the confining layer.
  • the Si 3 N 4 masking rings are selectively removed in a CF 4 plasma, resulting in a self- aligned geometry.
  • the sample is then Zn-diffused (540°C, 20 min) to improve the contacts and metallized with Ti-Au for the p-type contact and Ge-Ni-Au for the n-type contact.
  • the rings are then cleaved in half (or on a chord through the annulus) and the remaining three sides of the crystal are saw cut (SC) to prevent resonance across the edges.
  • SC saw cut
  • the 300 K cw light versus current (L-I) curve of a typical half-ring laser diode hereof is shown in Fig. 2.
  • the threshold current is - 105 mA (- 890 A/cm ).
  • the curve is linear above threshold with a total external differential quantum efficiency ( ⁇ of ⁇ 49%) and a total output power (both ends of the half ring) exceeding 40 mW.
  • the pulsed threshold (2 ⁇ s pulse width, 0.5% duty cycle) of this diode is 78 mA.
  • the pulsed (2 ⁇ s, 0.5% duty cycle) L-I characteristic of a moderate quality half-ring laser diode, fabricated as above, is shown in Fig. 3.
  • the diode threshold current is ⁇ 103 mA.
  • Longitudinal mode spectra show well defined modes, with single-mode operation occurring at 150 mA (Fig. 3, inset).
  • the mode spacing ( ⁇ ) is ⁇ 1.7 A, corresponding to a cavity length of ⁇ 560 ⁇ m. This is longer than the half- circumference ( ⁇ 470 ⁇ m) and may be due to some misalignment of the cleave (creating a longer cavity) or a longer effective path length caused by the curved resonator.
  • the near field (NF) intensity profiles of the laser diode of this example are collected with a f/0.95 25 mm focal length lens.
  • a low magnification view (Si MOS camera) with the diode operating at 130 Ma (pulsed) shows distinct emission from the two ends of the half-ring laser (Fig. 4(a)).
  • the 267 ⁇ m center-to-center separation agrees well with the device geometry.
  • the corresponding intensity profiles (CCD array image) are shown in Fig. 4(b). Both peaks exhibit asymmetry, with the intensity dropping off faster towards the outside diameter (OD) of the annulus. This asymmetry is more evident in the higher magnification view of the right-hand end (Fig. 4(c)).
  • Such asymmetric intensity profiles agree well with those calculated for a circular waveguide (see E. Marcatilli, Bell Syst. Tech. J. 48, 2103, 1969).
  • Polarization-resolved L-I characteristics indicate that the half-ring diodes lase in the TM mode. This behavior is opposite to that observed in conventional GaAs QWH laser diodes and in native-oxide defined linear resonator QWH laser diodes, which lase in the TE mode. The radiation losses in the native-oxide circular resonator for the TE modes are greater than for the TM modes, indicating application for mode filtering.
  • Fig. 5 shows the L-I characteristic of a native oxide ring laser diode fabricated in similar manner but on a lower (vertical) confinement Al ⁇ Ga l ⁇ As-GaAs QWH laser crystal (x ⁇ 0.6 confining layers) .
  • a cleave through the ring annulus permits laser light to leak out (inset of Fig. 5), with oscillation still maintained around the ring.
  • Fig. 6 is a simplified diagram of a laser device 600 made using the foregoing technique.
  • the device on GaAs substrate and buffer layers 610 and 615, includes an active region 630 between Al Ga As confining layers 640 and 650, of opposite conductivity types.
  • the active region includes the quantum well 633 between undoped A ⁇ Ga ⁇ As waveguide layers 635 and 637.
  • the diagram also shows the curved top contact stripe 660, the underlying GaAs cap layer 670, and bottom electrode 605.
  • the native oxide of this example, 680 extends through the entire upper confining layer 650 and slightly into the upper waveguide layer 637.
  • the native oxide of aluminum extends through the entire upper confining layer of the laser diode and even, to a small extent, into the waveguide region.
  • Applicant has discovered that effective optical confinement, tailored to obtain desired operating conditions, can be achieved with a thick (generally, about 3000 A or more) native oxide that does not necessarily extend through the entire confining layer.
  • a native oxide that extends through at least one-third of the confining layer is preferred.
  • Fig. 7 shows an embodiment of the invention having a linear stripe 760 and wherein the thick oxide 780 is controlled (e.g. by controlling the time of exposure and/or temperature in producing the native oxide) to extend about half way through the upper confining layer.
  • the aluminum fraction (x) of the Al ⁇ Ga 1 _ ⁇ As confining layers 740 and 750 is relatively low, for example about 0.4, which results in lower vertical (i.e., in the direction transverse the layers) confinement of the laser beam.
  • lower vertical confinement permits greater expansion of the beam into the confining layers and, accordingly, a larger effective lateral refractive index step encountered by the beam as a result of the native oxide in the confining layer.
  • Fig. 8 illustrates a passive curved waveguide in accordance with a form of the invention.
  • the GaAs cap layer 870, native oxide confining regions 880 (which extend about half way through the aluminum-bearing material in this case) , and the contact stripe 860, can be formed using the previously described techniques.
  • Figs. 9-18 illustrate configurations of lasers or waveguides (cross-sections of which may be, for example, of the types shown in Figs. 6, 7 and/or 8) that can be advantageously implemented utilizing the principles of the invention.
  • the white regions represent either the laser stripe configuration, which has thereunder, inter alia, a waveguide region with the index of refraction confinement in accordance with the present invention or, in the case of a waveguide, the index-confined waveguide region in accordance with the principles hereof.
  • Fig. 9 illustrates a ring configuration, with light energy travelling in both directions.
  • Fig. 10 illustrates a quarter ring, with light energy again travelling in both directions.
  • Fig.s 11 and 12 illustrate ring laser or waveguide configurations with tangentially coupled branches.
  • multi-stripe lasers are shown as being coupled by ring lasers, such as for phase locking.
  • the stripe spacing can be substantial.
  • Fig. 16 shows a similar arrangement, but with half-ring lasers, and Fig. 15 shows a series of coupled half-rings.
  • the locking or tuning provide by these configurations can result in enhanced longitudinal and/or transverse mode operation.
  • Fig. 17 shows curved sections in an "S-bend" arrangement for providing an active or passive lateral offset of the optical beam path.
  • Fig. 18 illustrates the surface configuration of a laser or waveguide which couples light in a single branch with four curved branches. '
  • a quantum well heterostructure is grown by metal-organic chemical vapor deposition ["MOCVD"] on an n-type GaAs substrate.
  • n- type buffer layers of GaAs ( ⁇ 0.5 ⁇ m) and an A1 Q 23 Ga Q 77 As ( ⁇ l ⁇ m) layer an Al Q 5 Ga 0 .As lower confining layer is grown to a thickness of ⁇ 1.5 ⁇ m.
  • the active region of the quantum well heterostructure is then grown, and includes a ⁇ 2100 A waveguide region of undoped Al 023 Ga Q 7? As with ⁇ 100 A undoped GaAs quantum well (QW) grown inside the waveguide region ⁇ 700 A from the lower confining layer.
  • An upper confining layer of p-type A1 Q 8 Ga Q 2 As is grown to a thickness of about 3500 A, and a heavily doped p-type GaAs contact layer is grown thereon, the contact layer having a thickness of about 800 A.
  • the position of QW is displaced from the center of the waveguide for more effective overlap of the high-gain region with the optical mode, which is displaced towards the substrate due to the asymmetric confining layers.
  • This asymmetry is purposely introduced to minimize the effects of the surface of the laser crystal (located ⁇ 3500 A from the waveguide) by shifting the optical field toward the substrate.
  • the shallow upper confining layer is desirable in order to minimize current spreading, allow-finer pattern definition, and improved heat dissipation with the crystal mounted p side "down" and thus the active region closer to the heat sink.
  • the thin upper confining layer structure combined with the p- type metallization may also serve to reflect light emitted toward the surface back into the crystal for improved device properties.
  • a laser diode fabricated using the described type of QW heterostructure, and comprising a linear array of small rectangular internal coupled cavities delineated by oxidation of the high-gap Al ⁇ Ga l ⁇ As upper confining layer, is described in N. El-Zein, F.A. Kish, N. Holonyak, Jr., A.R. Sugg, M.J. Ries, S.C. Smith, J.M. Dallesasse, and R.D. Burnham, "Native-Oxide Coupled-Cavity Al ⁇ Ga l ⁇ As-GaAs Quantum Well Heterostructure Laser Diodes", Appl. Phys. Lett. 59, 2838, November 25, 1991.]
  • a laser diode array in accordance with an embodiment hereof is fabricated by patterning ⁇ 1000 A of Si 3 N 4 into repeated (masked) rectangular cavities ( ⁇ 19 ⁇ m long, ⁇ 4 ⁇ m width, - 3 ⁇ m end-to-end spacing) , which are arranged lengthwise in two parallel stripes with - 1 ⁇ m separation.
  • the exposed GaAs cap is then removed by chemical etching (H 2 SO 4 :H 2 0 2 :H 2 0, 1:8:80) and the crystal is placed in an open- tube furnace (supplied with a N 2 carrier gas bubbled through H 2 0 at - 95°C) at 425°C for 20 min.
  • the crystal is then lapped and polished (on the substrate side) to a thickness of - 100 ⁇ m, and is metallized with Ti-Au across the oxide and the p-type GaAs "contacts" and with Ge-Ni-Au on the n-type substrate side.
  • the sample is then cleaved into 250-500 ⁇ m wide Fabry-Perot resonators, diced, and individual dies are mounted p-side down on In-coated Cu heat sinks for continuous (cw) operation.
  • the minicavities tend to store photons, making the mode amplitudes (marked with arrows) smaller (c of Fig. 20).
  • the mode structure near the peak of the spectrum in (c) is sufficiently complicated that it is not evident that at (b) 150 mA the single mode laser operation has shifted fully, from (a) 115mA, to a minicavity resonance (e.g., ⁇ h ⁇ ⁇ 6 meV vs. ⁇ E ⁇ 9 meV from resonance to resonance) . It is evident from (a) to (b) to (c) in Figs. 19 and 20, however, that single mode operation is turning-off and multi-mode operation, and weaker stimulated emission, is turning-on as the current is increased.
  • the unusual switching behavior of these 2-D array QWH stripe laser diodes is much more evident in Fig. 21.
  • the L-I characteristic shows that, with increasing current, the laser turns on and off twice.
  • the inset which corresponds to the peak of the L-I characteristic (> 12 mW, 415 mA, marked)
  • single mode operation still occurs.
  • the valley region between 220 and 300 mA broad-spectrum multi- mode operation similar to that of Fig. 20(c) occurs (data not shown) .
  • the dashed line of Fig. 21 shows, the emission intensity in this region is at or somewhat above spontaneous emission.
  • Most of the 2-D array lasers examined behaved as shown in Fig. 21.
  • the data of Fig. 22 show in some detail the behavior of the diode of Fig. 21 near the diamond-shaped point located at ⁇ 70 mA on the L-I characteristic.
  • the near field (NF) exhibits two intensity peaks expected of a twin linear array, with the spacing of 9.2 ⁇ m agreeing with the 2-D array width shown in the inset of Fig. 19.
  • the near field still exhibits twin intensity peaks, and the spectrum a single main mode corresponding to the left NF peak and significant satellite longitudinal modes corresponding to the right NF peak.
  • a small current change of 1 mA (71 -» 72 mA) produces abrupt switching:
  • the satellite longitudinal modes (Fig.
  • the data of Figures 19-22 demonstrates a laser diode having two parallel linear arrays of small coupled rectangular cavities delineated by oxidation of the high-gap Al ⁇ Ga ⁇ l As-GaAs QWH.
  • the two dimensional laser array exhibits mode switching and switching in the L-I characteristic with increasing current.
  • the laser operates in a single longitudinal modes in or near the spontaneous regime.
  • the resonances of the minicavities are evident in the spontaneous spectra in spite of small heating effects and carrier-induced changes in dielectric properties.
  • optimization of the geometry, size, and number of the minicavities, and their coupling may result in improved behavior of these devices.
  • the QW heterostructure crystal is substantially the same as the one described above in conjunction with the previous device.
  • the laser diode array is fabricated by first depositing ⁇ 1000 A of Si 3 N 4 on the crystal surface, which is then patterned into end-to-end repeated (masked) rectangular cavities (minicavities, 6 ⁇ m wide and 19 ⁇ m long on 22 ⁇ m centers) arranged lengthwise. Next, 6 ⁇ m photoresist (PR) stripes are patterned ⁇ 5 ⁇ m away from the linear array of minicavities.
  • PR photoresist
  • the patterned PR and Si 3 N 4 then serve as a mask for the chemical etching (H 2 SO 4 :H 2 0 2 :H 2 0, 1:8:80) of the GaAs cap layer, leaving the high-gap Al ⁇ Ga l ⁇ As exposed outside of the patterned regions.
  • the PR is then removed and the sample is placed immediately in an open-tube furnace (425°C) supplied with H 2 0 vapor in an N 2 carrier gas for 20 min. Again, this process results in the conversion of the exposed high-gap A ⁇ Ga ⁇ As to a low-index (n ⁇ 1.6) insulating native oxide located ⁇ 1000 A above the QWH waveguide region.
  • the patterned Si 3 N 4 and unetched GaAs regions are unaffected by this treatment.
  • the patterned Si 3 N 4 is then removed in a CF 4 plasma.
  • the inset of Fig. 23 shows the surface of the device after these processing steps.
  • the sample is Zn-diffused (540°C, 20 min) to increase the doping in the contact regions (labeled "GaAs" in Fig. 23).
  • the crystal is then lapped and polished to a thickness of ⁇ 125 ⁇ m and, again, metallized over the entire top surface with Ti-Au for p-type contacts and with Ge-Ni-Au for n-type contacts.
  • the crystal is cleaved, diced, and individual dies mounted on In-coated copper heat sinks for continuous (cw) operation.
  • the large amplitude switching properties of the single- stripe laser coupled to the active linear array are shown by the 300 K continuous (cw) L-I curve of Fig. 23.
  • the laser threshold current is 32 mA, and laser operation persists up to a current of 168 mA.
  • the diode switches abruptly from stimulated emission, ON (19.6 mW/facet, uncoated), to the spontaneous regime, OFF (0.4 mW/facet, uncoated). This behavior corresponds to a large ON:OFF power ratio of 49.
  • the L-I characteristic (cw 300 K) of another diode exhibiting similar switching behavior is shown in Fig. 24.
  • the laser threshold current is 27 mA, with the device exhibiting essentially a single ⁇ 5.5 ⁇ m-wide Gaussian near- field pattern (data not shown) .
  • This intensity pattern corresponds to laser operation of the ⁇ 6 ⁇ m wide uniform stripe (inset of Fig. 23), which is expected to reach threshold before the segmented linear array. From gain-loss considerations, the linear array with its repeated unpumped absorbing sections should have a higher laser threshold.
  • a single-stripe near-field pattern persists, i.e., only very weak output is observed from the linear array portion of the device.
  • the near-field pattern (300 K, cw operation) at (a) 99 mA just before the switching from ON to OFF, i.e., before switching from single-mode stimulated emission to spontaneous emission, is shown in the inset of Fig. 24. Similar to operation just above threshold, only a - 5.5 ⁇ m Gaussian near-field is observed at significant amplitude. After the diode switches OFF at (b) 100 mA, no pattern is observed on the same sensitivity scale of the CCD detector.
  • the diode of Fig. 24 operates in a single longitudinal mode ( ⁇ ⁇ 8353 A, data not shown) .
  • This behavior continues to the peak of the L-I curve of Fig. 24 (63 mA) , where the single mode operation "hops" to longer wavelength ( ⁇ ⁇ 8367 A, data not shown) .
  • the output occurs in a well developed single longitudinal mode.
  • the laser exhibits a side-mode suppression of 29 dB.
  • the mode hopping, and corresponding structure in the L-I curve (Fig. 24) is attributed to the interaction (interference) of the single laser stripe with side-coupled active linear array and its resonances and stop bands.
  • Fig. 25 Longitudinal mode spectra in the higher-current switching regime of the device of Fig. 24 are shown in Fig. 25.
  • the laser operates in a single longitudinal mode at ⁇ ⁇ 8415 A, which is shown as (a) in Fig. 25.
  • the longitudinal mode spectra appear as shown in (b) of Fig. 25.
  • the output consists of the spontaneous emission of the single stripe laser (group of lower energy modes) and the linear array (group of higher energy modes). The coupling of the linear array to the stripe laser leads to interference.
  • the resonances of the minicavities of the linear array are apparent (clearer in the laboratory data) at higher energy in the spectrum of Fig. 25(b) and are marked with arrows.
  • the spacing of these resonances corresponds to the ⁇ 19 ⁇ m minicavity length shown in the inset of Fig. 23. It is noted that the output in the OFF spontaneous regime (Fig. 25(b)) differs significantly from that observed in the spontaneous regime below laser threshold ( ⁇ 27 mA) , where only the longitudinal mode output of the single laser stripe (group of lower energy modes) is observed (data not shown).
  • the described switching and storage are fundamentally different from previously reported switching laser devices.
  • the ON-OFF switching behavior occurs in this embodiment in a single unbroken or uninterrupted laser stripe.
  • the switching behavior is owing to the influence (via sidewise coupling) of an active linear array.
  • the switching and bistability is effected by the periodic structure of the linear array (see H.G. Winful, J.H. Marburger, and E. Garmire, Appl. Phys. Lett. 35, 379 (1979); J. He and M. Cada, IEEE J. Quantum Electron. QE-27, 1182 (1991)) and the obvious inhomogeneous carrier distribution, and inhomogeneous operation, resulting from the native-oxide patterning of the array.
  • this embodiment sets forth a new form of optical switching element in which a conventional single-stripe laser is side-coupled to a linear array of coupled minilasers.
  • the resulting many-element twin-stripe laser is easily realized via native-oxide device processing.
  • the planar devices exhibit large hysteresis in the L-I curve, with large amplitude switching from the peak of the stimulated emission regime (ON) to the spontaneous regime (OFF) .
  • Changes in the coupling e.g., the spacing between the laser stripe and linear array and between the array elements, and in the geometry of the structure should improve the switching behavior of these lasers.
  • Independent control of the current (carrier population) in the single laser stripe in the linear array e.g., via a third terminal electrode, should allow control of the switching behavior, and other variations are possible.
  • Fig. 26 shows a part of the surface of the device described in conjunction with Figures 23-25, and is used as a reference to show the cross-sections used for the illustrations of Figures 27-29.
  • the stripe is labelled 1210 and the minicavities, or portions thereof, are labelled 1221-1225.
  • the cross-section 13-13 is taken through the stripe 1210 and an adjacent minicavity 1224.
  • the illustrated layers include the bottom contact metallization 1250 (it being understood throughout that references to “bottom” or “top” are for ease of description, as the device may be mounted and used in any desired orientation) , followed, in ascending order, by the n- type GaAs substrate layer 1255, the n-type GaAs buffer layer 1258, the n-type Al Q 23 Ga 077 As buffer layer 1260, the n-type Al 05 Ga 05 As lower confining layer 1-263, and active region 1270 that includes a GaAs quantum well layer 1271 between waveguide layers 1273 and 1275 of undoped Al 023 Ga 077 As. Above the active region is the upper confining layer 1278 of p-type Al 0 B Ga Q2 As.
  • the layer thicknesses may be, for example, as previously indicated above for the experimental device.
  • the p-type GaAs contact 1281 and the p-type GaAs contact 1283 respectively define the contact positions of the stripe 1210 and the minicavity 1225 of Fig. 26.
  • the native oxide is shown at 1291, 1292, and 1293, and, in this example, has a thickness of about 1300 A The oxide also extends somewhat under the GaAs contact regions.
  • the top (p-side) metallization is labeled 1240.
  • Fig. 28 illustrates the cross-section defined by arrows 14-14 of Fig. 26. In this view, only the contact region 1281 of the stripe 1210 is visible. The oxide (1294) extends continuously to the right of the stripe.
  • Fig. 19 shows the cross-section defined by arrows 15-15 of Fig. 26. This view is longitudinally through the minicavities, with two minicavities being shown between three oxide regions 1296, 1297, 1298. The longitudinal dimension of the contact 1283 is seen in this view.
  • operation may be "two terminal", such as by applying the electrical potential between the bottom electrode and the top common metallization.
  • the device can alternatively be made for operation as a three terminal or multiple terminal device.
  • Fig. 30 illustrates a device having a stripe 1610 with mini cavities 1620 on both sides, each line having a common metallization (represented by the joining lines between minicavities) and its own terminal, so that the device can be operated with four independent terminals, with three terminals (for example, the terminals of only two adjacent lines and the bottom terminal, or with the two outside lines in common) or two terminals, with all three lines in common.
  • Fig. 31 illustrates a two-dimensional array of adjacent lines of mini cavities, with individual terminals coupled with the mini cavities. It will be understood that a terminal can be coupled with any desired combination or group of cavities or minicavities.
  • FIG. 32-39 illustrate some representative embodiments (with bottom electrode and various possible top electrodes not shown) .
  • Fig. 32 there is shown a ring laser which is divided into curved minicavities 1815, to obtain the types of effects described in N. El-Zein, F.A. Kish, N. Holonyak, Jr., A.R. Sugg, M.J. Ries, S.C. Smith, J.M. Dallesasse, and R.D.
  • Fig. 33 illustrates two concentric ring lasers, each divided into minicavities 1915, so that lateral coupling can be achieved, as first described in conjunction with Figures 19-22 above for the case of straight line arrays.
  • Fig. 35 illustrates a circular configuration with sector-shaped minicavities 2115 separated by radial "spokes" of native oxide.
  • Fig. 36 shows a ring laser 2210 laterally coupled with a stripe laser 2220.
  • the ring is divided into minicavities 2315
  • the stripe is divided into minicavities 2415
  • both the ring and the stripe are divided into minicavities (2515 and 2525, respectively) .
  • Fig. 40 illustrates, in cross-section, a form of the invention which couples cavities with different longitudinal mode characteristics, in the form of a vertical cavity laser array.
  • Vertical cavity lasers are well known in the art (see, for example, H. Soda et al. Japan J. Appl. Phys. 18, 59 (1979) and K. Iga et al.. Electron Lett. 23, 134 (1987), and include, as in the lefthand unit of Fig. 40, a bottom contact 2610 on a substrate (e.g.
  • the superlattices may comprise a number of alternating layers of AlAs and GaAs [or Al ⁇ Ga l ⁇ As and Al Ga r yAs, ' x ⁇ y -xx, ' or combinations of AlXGa1,-xAs and conductive dielectric stacks (e.g.
  • the active region may comprise Al 0 .Ga 0 g As (or GaAs) waveguides layers with a GaAs (or In 01 Ga o g As) quantum well layer with total thickness of typically ⁇ 250 A.
  • the contacts at the surface may comprise for example Au or Ag with a standard (e.g. Ge-Au) backside (substrate) side contact.
  • a two-dimensional vertical cavity coupled array of such devices is described for example in D.G. Deppe, J.P. Van der Ziel, Nasesh Chand, G.J. Zydzik, and S.N.G. Chu, Appl. Phys. Lett. 56, 2089 (1990). Briefly, in operation, the multiple reflections from the superlattice interfaces provide a relatively short effective cavity length (typically ⁇ 5 ⁇ m) from the limited thickness device, and the cavities are coupled evanescently.
  • adjacent vertical cavity laser units are provided with active regions of different thicknesses, as illustrated in Fig. 40, where the active region 2630' is substantially thicker than the active region thickness of its neighboring unit.
  • the quantum well layer is continuous through adjacent active regions, although this is not necessary.
  • the superlattice layers above the active region 2630* Variation of the upper or lower superlattice thickness laterally varies the effective lateral mirror reflectivity. Such variations may also be employed with a uniform thickness active region to achieve local variations in the cavity structure.
  • other schemes may be employed to couple such devices such as varying the mirror (e.g. superlattice) angles to directly reflect some of the light from one cavity into adjacent cavities.
  • vertical cavities having substantially different effective cavity lengths means that the cavities have substantially different longitudinal mode characteristics, as previously defined.
  • the active regions of adjacent units may comprise different materials.
  • adjacent units with superlattices of different thicknesses, or superlattices of different configurations An example of the latter would be to provide one unit having superlattices of alternating 100 A GaAs and AlAs layers and the other unit with superlattices having alternating 200 A GaAs layers and 100 A AlAs layers, which results in different effective cavity lengths.
  • Fig. 41 illustrates a checkerboard-type array of such units, with the cross-hatched units representing the units having the thicker active regions.
  • the array can be operated as a two terminal device, with the top contacts coupled in common, and potential applied between the top and bottom contact, or can be driven as a three terminal or multiple terminal device with separate connections to contacts.
  • Various other shapes and configurations in one-dimension or two-dimensions can be utilized.
  • the growth may be terminated at the active region (2630' ).
  • a two-dimensional pattern e.g. a checkerboard
  • a two-dimensional pattern is then masked using standard photolithography techniques and the sample is subjected to chemical etching to remove a portion of the active region (2636) in the unmasked areas.
  • the photoresist is then removed and the upper p-type supperlattice is grown on the patterned active region, such as by MOCVD or MBE (molecular beam epitaxy) .
  • MOCVD molecular beam epitaxy
  • a circular (dot) metallization can then be applied on the upper p-type supperlattice for contact and reflectivity purposes.
  • devices can integrate the aluminum-bearing III-V semiconductor material (from which the native oxide is formed) with other non-III-V semiconductor materials.
  • laterally coupled cavities as described herein can be utilized for tuning as well as indicated functions such as switching. The lateral coupling described herein is particularly facilitated by using the native oxide formed in an aluminum-bearing III-V semiconductor material to separate laterally coupled cavities.
  • less preferred cavity definition can alternatively be implemented by techniques such as multiple regrowths/overgrowths, etch and regrowth/overgrowth, ridge formation, ridge formation and overgrowth, impurity induced layer disordering, and proton implantation.

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Abstract

L'invention se rapporte à des techniques et à des dispositifs améliorés utilisant un matériau semi-conducteur du groupe III à V comportant de l'aluminium et un oxyde natif d'aluminium constitué dans le matériau semi-conducteur. Dans un mode de réalisation de l'invention, deux rangées linéaires de minicavités couplées à leurs extrémités, définies par un oxyde natif d'un matériau semi-conducteur du groupe III à V comportant de l'aluminium, sont disposées côte à côte, de façon à obtenir une rangée bidimensionnelle, ainsi qu'un couplage latéral entre les rangées linéaires. La rangée bidimensionnelle présente une commutation de mode et une commutation multiple de la caractéristique (L-I) de puissance lumineuse (L)/courant (I) avec une augmentation de l'intensité du courant. Dans un autre mode de réalisation, un laser à bande (1210) est couplé transversalement (ou couplé latéralement) avec une rangée linéaire de minicavités couplées à leurs extrémités (1221-1275). La caractéristique lumière/courant (L-I) d'une structure définie par un oxyde natif de ce type est une démonstration de la bistabilité et de la commutation.
EP93908605A 1992-03-30 1993-03-26 Dispositifs et techniques optiques a semi-conducteur. Withdrawn EP0634052A4 (fr)

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US07/927,822 US5353295A (en) 1992-08-10 1992-08-10 Semiconductor laser device with coupled cavities
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US5550081A (en) * 1994-04-08 1996-08-27 Board Of Trustees Of The University Of Illinois Method of fabricating a semiconductor device by oxidizing aluminum-bearing 1H-V semiconductor in water vapor environment
US6117699A (en) * 1998-04-10 2000-09-12 Hewlett-Packard Company Monolithic multiple wavelength VCSEL array
US7561770B2 (en) * 2007-07-30 2009-07-14 Hewlett-Packard Development Company, L.P. Microresonator systems and methods of fabricating the same
GB2478602B (en) * 2010-03-12 2014-09-03 Toshiba Res Europ Ltd A semiconductor device and method of manufacturing a semiconductor device
US11658453B2 (en) * 2018-01-29 2023-05-23 Ronald LaComb Concentric cylindrical circumferential laser
FR3078834B1 (fr) * 2018-03-08 2020-03-27 Commissariat A L'energie Atomique Et Aux Energies Alternatives Dispositif d’emission lumineuse comportant au moins un vcsel et une lentille de diffusion
CN115799990A (zh) * 2022-11-14 2023-03-14 中国科学院半导体研究所 一种高铝组分的氧化限制半导体激光器及其制备方法

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EP0634052A4 (fr) 1997-08-27
JP3726240B2 (ja) 2005-12-14
AU3936893A (en) 1993-11-08
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JPH07505503A (ja) 1995-06-15
CA2132986A1 (fr) 1993-10-14
WO1993020581A1 (fr) 1993-10-14

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