CN100424897C - Gallium Nitride-Based Infrared-Visible Wavelength Conversion Detector - Google Patents

Abstract

The present invention discloses an infrared-visible wavelength converting detector, which is made of gallium nitride (GaN) base material and can couple a multi-quantum well infrared detector and a light emitting diode on the same chip. The multi-quantum well infrared detector (QWIP) can convert infrared radiation signals into infrared electrooptical signals, and the infrared electrooptical signals are converted into optical signals of a visible waveband via the light emitting diode. The present invention has the advantages of realizing the upconversion of biasing voltage lower longwave thermal infrared to a visible light waveband, users can directly observe with eyes, and the present invention simplifies the structure of detecting systems. The material preparation of the present invention device has the advantages of mature technique and good material homogeneity.

Description

Gallium Nitride-Based Infrared-Visible Wavelength Conversion Detector

technical field

The invention relates to an infrared detector and a light-emitting diode, in particular to an infrared-visible wavelength conversion detector made of gallium nitride (GaN)-based material and coupled in series with the infrared detector and the light-emitting diode on the same chip.

Background technique

Traditional infrared detectors mostly use focal plane array technology. The signal of each photodetection unit in the array is sent to an external silicon readout circuit and converted into a video signal for output. This structure requires each photosensitive element to form a corresponding interconnect point on the silicon readout circuit. Therefore, it is necessary to accurately convert the information on the focal plane array to a correspondingly large number of interconnected nodes. Integrated systems between dissimilar materials are expensive and unreliable, and are especially susceptible to thermal shock from refrigeration and non-refrigeration cycles.

In recent years, with the maturity of GaN-based quantum well material preparation process and light-emitting diode technology, the infrared detector with sub-band transition of GaN/AlGaN quantum well grown in series and the up-conversion of light-emitting diode with inter-band transition of GaN-based single quantum well have been made possible. devices become possible. The device can convert infrared light into green light, which is the most sensitive to human eyes, through the effective coupling of GaN-based quantum well infrared detectors and light-emitting diodes, and realize direct observation by human eyes. It not only has a more mature material preparation process and better material uniformity than narrow-band material HgCdTe devices; it also avoids the problems of readout circuit interconnection and large cooling capacity requirements faced by general infrared detectors, and also saves the usual GaAs/AlGaAs-based The CCD imaging equipment required for the conversion of the mid-to-far infrared to the near-infrared of the quantum well simplifies the system structure and reduces the cost.

Contents of the invention

Based on the existing situation above, the object of the present invention is to propose an infrared-visible wavelength conversion detector in which a GaN-based multi-quantum well infrared detector and a visible light emitting diode are coupled in series.

In order to achieve the above object, the GaN-based infrared-visible wavelength conversion detector of the present invention includes a substrate 1, on which the lower electrode layer 2, the multi-quantum well infrared detector 3, the Al _a Ga _1-a N transition Layer 4, single quantum well light emitting diode 5, upper electrode layer 6.

The multi-quantum well infrared detector 3 is composed of _{AlbGa1 -bN} potential barrier layer/GaN potential well layer grown alternately for 50 cycles, and finally adds a layer of _{AlbGa1 -bN} potential barrier layer to end . The thickness of the GaN potential well layer and the Al _b Ga _1-b N barrier layer and the value of b are related to the infrared wavelength to be detected.

The single quantum well light emitting diode 5 is sequentially composed of an In _x Ga _1-x N barrier layer, an In _y Ga _1-y N active potential well layer and an Al _a Ga _1-a N barrier layer. The light-emitting wavelength of the light-emitting diode can be changed from blue to yellow by adjusting the y value in the undoped In _y Ga _1-y N active layer from 0.2 to 0.7.

The present invention adopts _{AlbGa1 -bN} /GaN as infrared detector multi-quantum well growth material, and its reason is that it has larger conduction band order, can make the absorption wavelength of transition between subbands have larger span (0.7 Micron to 14 microns), by adjusting the thickness of the GaN quantum well and the height of the AlGaN barrier, the energy between the subbands of the GaN quantum well can exactly correspond to the energy of the detected infrared radiation photon, and at the same time the first excited state is in the same state as the potential barrier In the quasi-bound state of resonance or in the continuum state above the potential barrier, it can be used for infrared detection. In the single quantum well green light-emitting diode, the bandgap width of the active potential well layer In _y Ga _1-y N changes with the change of In content (1.9-3.5eV), and the inter-band gap can be realized by properly adjusting the composition. The most sensitive green light emitted by the eye can be made into a light-emitting diode in the green band. Therefore, the choice of GaN-based materials can not only grow quantum well infrared detectors, but also prepare light-emitting diodes in the green band, which can well realize coupling integration.

The basic working process of the device of the present invention is: when a constant bias voltage is applied to both ends of the series device, the bias voltage will simultaneously act on the multi-quantum well infrared detector (QWIP) device and the green light emitting diode (LED) device. When infrared light enters the QWIP through the optical system, the absorption of infrared radiation by the QWIP causes subband transitions to generate mobile free electrons. Some of these electrons are injected into the LED under the action of an electric field, and recombine with holes in the active area of the LED to emit visible light. Since QWIP is a photoconductive device, when it absorbs different intensities of infrared radiation, its resistance decreases differently, so the voltage applied to both ends of the LED is also correspondingly different, resulting in different luminous intensity of the LED. Therefore, if the incident radiation is not uniform, after the QWIP electrons are injected into the LED, the intensity of the corresponding output visible light will be not uniform. That is, in the absence of obvious optical crosstalk, the spatial distribution of the output green light repeats the distribution of the photogenerated current in QWIP, which in turn also repeats the spatial distribution of the input infrared radiation. In short, through this series of non-photosensitive components, the upconversion of thermal infrared photons to visible green light photons is realized, that is, the conversion of infrared images into green light band images that can be directly observed by the eyes is realized.

The quantum well infrared detector in the up-conversion device can be either N-type or P-type, and it only needs to pay attention to the bias voltage applied corresponding to the LED terminal. However, due to the transition selection rule, the N-type QWIP must etch a grating on it to effectively absorb the vertically incident infrared light.

Device of the present invention has following positive effect and advantage:

1. Compared with the CCD imaging equipment required by the general up-conversion device from mid-far infrared to near-infrared, the device of the present invention can be directly observed by human eyes, which simplifies the system structure.

2. Compared with the traditional infrared detector, the device of the present invention does not need a separate photosensitive element, avoids the Si readout circuit, thus does not involve the problem of circuit interconnection, avoids the problem that the usual focal plane device needs a large cooling capacity, and reduces The technical difficulty and cost of device fabrication are reduced.

3. The material used in the device of the present invention has a mature preparation process and good material uniformity.

Description of drawings

Fig. 1 is a schematic diagram of the structure and function implementation of the detector of the present invention.

Fig. 2 is a schematic diagram of the energy band and physical process of the multi-quantum well infrared detector-green light-emitting diode.

Detailed ways

The following is an example of an infrared-visible wavelength conversion detector coupled in series with an N-type QWIP and a green LED, wherein the infrared absorption peak of the N-type QWIP is set at around 2.9 microns, and the peak wavelength of the EL spectrum of the LED is at 525nm. The figure further elaborates the specific embodiment of the present invention:

The detector of the present invention utilizes a typical technique of semiconductor material epitaxy, such as molecular beam epitaxy _technique , metal organic chemical vapor deposition technique, etc., and is arranged and grown sequentially on _Al2O3 sapphire substrate 1:

n*-GaN lower electrode layer 2;

Alternately grow 50 cycles of 10nm thick Al _0.35 Ga _0.65 N barrier layers (51 layers) and 3.5nm thick GaN potential well layers (50 layers), where the doping concentration in the GaN quantum wells is 8*10 ¹⁷ cm ^-3 , thereby forming an infrared detector 3 with multiple quantum wells;

100nm thick Al _0.1 Ga _0.9 N transition layer 4;

Then there is a 50nm thick N-type In _0.05 Ga _0.95 N barrier layer and a 2nm thick undoped In _0.43 Ga _0.57 N active layer and a 100nm P-type Al _0.1 Ga _0.9 N barrier layer to form a single quantum well LED 5;

Next is a 200nm P-type GaN upper electrode layer 6, and a grating layer 7 is etched thereon to complete the preparation of the infrared-visible wavelength conversion detector.

In this embodiment, the single quantum well LED is selected because the single quantum well has higher luminous intensity and color purity than the double heterostructure LED.

Claims (2)

1. a gallium nitride-base infrared visable wavelength conversion detector comprises substrate (1), it is characterized in that:

On substrate (1), be arranged in order growth lower electrode layer (2), multiple quantum well infrared detector (3), Al _aGa _1-aN transition zone (4), single quantum well light-emitting diode (5), upper electrode layer (6);

Said multiple quantum well infrared detector (3) is by the alternating growth Al in 50 cycles _bGa _1-bN barrier layer/GaN potential well layer adds one deck Al at last _bGa _1-bThe N barrier layer is formed; GaN potential well layer and Al _bGa _1-bThe bed thickness of N barrier layer is relevant with the infrared wavelength that will survey with the value of b;

Said single quantum well light-emitting diode (5) is successively by In _xGa _1-xN barrier layer, In _yGa _1-yActive potential well layer of N and Al _aGa _1-aThe N barrier layer is formed, and the emission wavelength of light-emitting diode can be by regulating unadulterated In _yGa _1-yY value in the N active layer, from 0.2 to 0.7, make it change emission wavelength from the blueness to the yellow.

2. according to a kind of gallium nitride-base infrared visable wavelength conversion detector of claim 1, it is characterized in that: said multiple quantum well infrared detector both can be the N type, also can be the P type, if the N type then needs to form grating layer (7) on the top of upper electrode layer (6) by etching.

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