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GB2181299A - Semiconductor devices - Google Patents

Semiconductor devices Download PDF

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Publication number
GB2181299A
GB2181299A GB08622390A GB8622390A GB2181299A GB 2181299 A GB2181299 A GB 2181299A GB 08622390 A GB08622390 A GB 08622390A GB 8622390 A GB8622390 A GB 8622390A GB 2181299 A GB2181299 A GB 2181299A
Authority
GB
United Kingdom
Prior art keywords
layer
region
layers
diode
doped gaas
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.)
Granted
Application number
GB08622390A
Other versions
GB8622390D0 (en
GB2181299B (en
Inventor
Nigel Roderick Couch
Michael Joseph Kelly
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.)
General Electric Company PLC
Original Assignee
General Electric Company PLC
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 GB858524070A external-priority patent/GB8524070D0/en
Application filed by General Electric Company PLC filed Critical General Electric Company PLC
Priority to GB8622390A priority Critical patent/GB2181299B/en
Publication of GB8622390D0 publication Critical patent/GB8622390D0/en
Publication of GB2181299A publication Critical patent/GB2181299A/en
Application granted granted Critical
Publication of GB2181299B publication Critical patent/GB2181299B/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
    • H10D62/80—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials
    • H10D62/81—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials of structures exhibiting quantum-confinement effects, e.g. single quantum wells; of structures having periodic or quasi-periodic potential variation
    • H10D62/815—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials of structures exhibiting quantum-confinement effects, e.g. single quantum wells; of structures having periodic or quasi-periodic potential variation of structures having periodic or quasi-periodic potential variation, e.g. superlattices or multiple quantum wells [MQW]
    • H10D62/8161—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials of structures exhibiting quantum-confinement effects, e.g. single quantum wells; of structures having periodic or quasi-periodic potential variation of structures having periodic or quasi-periodic potential variation, e.g. superlattices or multiple quantum wells [MQW] potential variation due to variations in composition or crystallinity, e.g. heterojunction superlattices
    • H10D62/8162—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials of structures exhibiting quantum-confinement effects, e.g. single quantum wells; of structures having periodic or quasi-periodic potential variation of structures having periodic or quasi-periodic potential variation, e.g. superlattices or multiple quantum wells [MQW] potential variation due to variations in composition or crystallinity, e.g. heterojunction superlattices having quantum effects only in the vertical direction, i.e. layered structures having quantum effects solely resulting from vertical potential variation
    • H10D62/8164—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials of structures exhibiting quantum-confinement effects, e.g. single quantum wells; of structures having periodic or quasi-periodic potential variation of structures having periodic or quasi-periodic potential variation, e.g. superlattices or multiple quantum wells [MQW] potential variation due to variations in composition or crystallinity, e.g. heterojunction superlattices having quantum effects only in the vertical direction, i.e. layered structures having quantum effects solely resulting from vertical potential variation comprising only semiconductor materials 
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
    • H10D62/80—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials
    • H10D62/82—Heterojunctions
    • H10D62/824—Heterojunctions comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D8/00—Diodes
    • H10D8/70—Tunnel-effect diodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/16—Photovoltaic cells having only PN heterojunction potential barriers
    • H10F10/163—Photovoltaic cells having only PN heterojunction potential barriers comprising only Group III-V materials, e.g. GaAs/AlGaAs or InP/GaInAs photovoltaic cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation
    • H10F30/22—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes
    • H10F30/222—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes the potential barrier being a PN heterojunction
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/14—Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
    • H10F77/146—Superlattices; Multiple quantum well structures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/544—Solar cells from Group III-V materials

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nanotechnology (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biophysics (AREA)
  • Optics & Photonics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Led Devices (AREA)
  • Bipolar Transistors (AREA)

Description

SPECIFICATION Semiconductor devices This invention relates to semiconductor devices. In particulartheinvention relatestosemiconductordevices of a diode form.
It is an object of the present invention to provide a semiconductor device of a diode form which displays novel electronic properties leading to tailorable current-voltage characteristics.
According to the present invention a semiconductor device comprises: first and second layers of semiconductor material each of different conductivity type; and a region of semiconductor material sandwiched between the first and second layers, the mat erial ofwhich the region is formed being ofsubstanti- ally the same composition as the first layeratthe edgeofthe region adjacenttothefirst layer, and varying in composition linearly on the running average in the direction between the first and second layers, such that the region forms a heterojunction with the second layer.
In oneparticulardevice in accordancewiththeinvention the region is formed of a material whose composition varies continuously along said direction.
In another particular device in accordance with the invention the region comprises a stack of alternating layers of two different semiconductor materials which together define a superlattice along said direction, the relative thicknesses ofthe alternating layers varying along said direction.
Two diodes in accordance with the invention will now be described, by way of example only, with reference to the accompanying figures in which: Figure lisa schematic side view ofthe first diode; Figure2 illustrates the composition through the first diode, together with the corresponding energy bands; Figure 3 shows the current voltage characteristic of thefirstdiode; Figure 4illustrates the composition through the second diode, together with the corresponding energy bands; Figure 5shows the current-voltage characteristic of the second diode, and Figure 6shows the current-voltage characteristic ofthe second diode with an amplified current scale to that of Figure 5.
Referring firstly to Figure 1, the first diode comprises a 5000thick layerofp doped GaAs 1 and a 5000 layer of n doped GaAs 3, a 500 thick layer of A1 xGaq xAs 5 being sandwiched between the layers 1, 3. As can be seen in Figure 2, theAl contentxofthe layer5varies linearly from zero adjacenttothe ptype layer 1 ,to 0.3 adjacent to then type layer3,this being accompanied by a corresponding decrease in the Ga content ofthe layer.At either side of the layers 1,3 there are provided respective n+ doped GaAs 7 and p+ doped GaAs 9 capping layers each 5000Athick, the p+ layer lying on an + doped GaAs substrate 11.
Respective metal contacts 13, 15 for the device are provided on the free surface ofthe substrate 11 and the p+ capping layer 9. The doping levels ofthe layers 1,3,7,9 are as indicated in Figure 2. Thethick- ness ofthe layer of A1 xGa1 x5 is chosen to be in the order of the electron mean free path, this layer 5 for- ming part ofthe depletion region ofthe device and producing a discontinuity in the conduction band edge as shown in Figure 2.
The current-voltage plot of the first diode meas ured at 70K is shown in Figure 3, both the dark cur- rent, and the photocurrent produced when the diode is illuminated being shown. As can be seen the device exhibits a large photovoltaic effect. This indicates use of the device as a high performance photodetector, or as a solar cell.
Referring now to Figure 4the second diode to be described is ofthe same general form asthefirst diode and therefore corresponding parts ofthe second diode are correspondingly labelled. The layer of Al xGaa xAs 5 is however replaced in the second diode by a stack 16 of alternating layers of GaAs 17, 19 21, 23 and 25 andA1As 27, 29, 31, 33 and 35,these layers constituting a compositional superlattice. The thickness of each of the GaAs layers decreases I inearly along the direction from the p doped layer 1 to then doped layer 3 from 94Ato 70 , the thickness of each A1As layer correspondingly increasing from 6A to 30 . The running average composition of the stack 16 in the direction between the layers 1,3 is as shown in Figure 4 by the dotted line, this in fact being equivalent to the linearly graded A1xGA1-xAs composition ofthe layer 5 ofthe first diode. The conduction band edgeforthe second diode is thus of similar form to that shown in Figure 2 for the first diode.
Figure 5 illustrates the general form ofthe current voltage plot for the second diode where it can be seen the diode exhibits negative differential con ductivityfor applied voltages of about 1.7 volts. Thus such a diode finds application as a microwave local oscillator.
Referring now also to the more detailed current voltage plot of Figure 6, trace a illustrates the current voltage plot measured at4Kforthe second diode with the device kept in the dark, whilsttraceb illustrates the corresponding current voltage plot whilst the device is illuminated with a continuous wave HeNe laser. As can be seen from plot a, the dark currentforthe second device is less than 11 pA over the voltage range -I- + 1.1 vto -4.5vwith no discernable voltage dependence.Forvoltages of greaterthan 1 .52v, the current is controlled by the turn on of the p-n junction, constituted by the layers 1,3 and resonant tunnelling through the barriers constituted by the layers 27, 29, 31 33 and 35 of A1As within the superlattice separating the p doped GaAs layer 1 and then doped GaAs layer 3. Breakdown ofthe device in reverse bias is found to occur at -25V. As can be seen from plotb of Figure6, under illumination the second diode exhibits a photovoltage and an associated photocurrent. In reverse bias, the photocurrent is found to saturate at -3.0V at a current of 1 08 > A. The short circuit current is measured to be 85A, with the open circuit voltage being 0.94v.
At room temperature similar current-voltage characteristics for the second diode are obtained, although a leakage current superimposed equally on both the dark and photo-currents is produced. The photo-current is still found to saturate at -3.0V at room temperature however, at a value of iBSijA.
The existance of the low dark currentforthe second diode thus indicates a numberofopto- electronic applications forthis second diode which utilise the large increase in sensitivity over that of conventional p-i-n diodes.
It will be appreciated thatwhilstthe diodes descri bed by way of example are based on the two materials GaAs and A1As, diodes in accordance with the invention can be formed from any pair of compound semiconductorsthatarecapable of mutual epitaxial growth. This includesthe pairs of materials InGaAs/ InP, InGaAsP/lnP and HgCdTe/CdTe which have part icularapplication in systemsforoptical communications and use in the infrared.
It will also be appreciated that whilst in the diodes described before byway of example particular layer thicknesses have been specified, these may be readily varied in accordance with the particular diode characteristics required. Generally the thickness of the layer of varying composition will be up to about ten times the electron mean free path for the materials used. Forth in layers ofvarying composition, of athickness intheorderof20 ,tunnelling and inter- ference effects will dominate the characteristics of the diode, these effects slowly dying off with increasing thickness.
It will also be appreciated thatwhilst in the diodes described before byway of example the particular doping levels specified in Figures 2 and 4 are used, these levels may also be readily varied in accordance with the required device characteristics.

Claims (7)

1. A semiconductor device comprising: firstand second layers of semiconductor material each of different conductivity type; and a region of semiconductor material sandwiched between the first and second layers, the material of which the region is formed being of substantially the same composition as the first layer at the edge of the region adjacentto the first layer, and varying in composition linearly on the running average in the direction between the first and second layers, such thatthe region forms a het erojunction with the second layer.
2. A device according to Claim 1 in which the re- gion is formed of a material whose composition varies continuously along said direction.
3. Adeviceaccordingto Claim 2 inwhich thefirst layer is formed of p doped GaAs, the second layer is formed of n doped GaAs, and the region is formed of A1xGa1 wherex is 0 adjacenttothe first layer, and increases linearly in said direction.
4. A device according to Claim 3 in which xis 0.3 adjacentto the second layer.
5. A device according to Claim 1 in which the region comprises a stock of alternating layers of two different semiconductor materials which together define a superlattice along said direction,the relative thicknesses of the alternating layers varying along said direction.
6. Adeviceaccordingto Claim 5 in which the first layer is formed of p doped GaAs, the second layer is formed of n doped GaAs, and the alternating layers are of GaAs and A1As.
7. A semiconductor device substantially as here it before described with reference to Figures 1,2 and 3 or Figures 4,5 and 6 ofthe accompanying drawings.
GB8622390A 1985-09-30 1986-09-17 Semiconductor devices Expired GB2181299B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8622390A GB2181299B (en) 1985-09-30 1986-09-17 Semiconductor devices

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB858524070A GB8524070D0 (en) 1985-09-30 1985-09-30 Semiconductor devices
GB8530294 1985-12-09
GB8622390A GB2181299B (en) 1985-09-30 1986-09-17 Semiconductor devices

Publications (3)

Publication Number Publication Date
GB8622390D0 GB8622390D0 (en) 1986-10-22
GB2181299A true GB2181299A (en) 1987-04-15
GB2181299B GB2181299B (en) 1989-03-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8622390A Expired GB2181299B (en) 1985-09-30 1986-09-17 Semiconductor devices

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0134069A2 (en) * 1983-05-17 1985-03-13 Kabushiki Kaisha Toshiba Bipolar transistor having a heterojunction between base and collector

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0632339B2 (en) * 1984-12-18 1994-04-27 キヤノン株式会社 Semiconductor laser

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0134069A2 (en) * 1983-05-17 1985-03-13 Kabushiki Kaisha Toshiba Bipolar transistor having a heterojunction between base and collector

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Publication number Publication date
GB8622390D0 (en) 1986-10-22
GB2181299B (en) 1989-03-15

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19920917