A current polarity controllable semiconductor photodetector and a device provided with the same

Abstract

The application discloses a semiconductor photoelectric detector with controllable current polarity and a device provided with the same. A lower polarization layer and an upper polarization layer in an active layer of the semiconductor photoelectric detector are a heterostructure, the band gap of the lower polarization layer is greater or smaller than that of the upper polarization layer, negative polarization charges or positive polarization charges are accumulated on the contact interface of the lower polarization layer and the upper polarization layer, and the absolute value of a heterojunction barrier formed at the contact interface is greater than 0.3eV. The application utilizes the strong polarization effect of a compound semiconductor, forms a heterojunction barrier with an interface double-side depletion layer at a heterojunction interface, irradiates the device with light of a wave band corresponding to the band gap of the lower polarization layer and the upper polarization layer under a specific bias voltage range, and opposite or same response currents can be formed. Thus, the current polarity can be controlled according to the bias voltage and the incident light, and functions such as a photo-controlled logic gate, a light wave band identification or a double-wave band light high-gain detection can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor photoelectric conversion, and more particularly to a semiconductor photoelectric detector with controllable current polarity and a device provided with the same. BACKGROUND

[0002] The basic working principle of a semiconductor photoelectric detector is that a photon with energy greater than or equal to the band gap of a semiconductor excites an electron-hole pair, and under the action of an applied bias and / or an internal electric field, carrier transport is generated to form a current signal collected by an electrode. Semiconductor photoelectric detection devices mainly include photodetectors and solar cells, among which the solar cell is a pn junction barrier device, and the photodetector further includes a photoconductive detector, a Schottky barrier photodiode, a metal-insulator-semiconductor photodetector, an avalanche photodiode, and a phototransistor. Regardless of which photoelectric detector, the direction of carrier transport (current polarity) is unidirectional when the applied bias is constant, and the size of the current changes with the intensity of the incident light, and thus the intensity of the incident light signal can be confirmed. The unidirectional carrier transport photodiode can be used as a photologic gate, but usually only a single logic gate such as "and" or "or" can be implemented.

[0003] With the advent of the fourth industrial revolution era centered on the Internet, the Internet of Things, big data, artificial intelligence, etc., the existing circuits or processors based on electronic logic gates will be limited in terms of computing large data sets due to the insufficient performance of switching, operation, and calculation. Therefore, it is of practical and important significance to develop new logic gates to achieve faster computing with lower power consumption to meet the needs of the upcoming new computing trend.

[0004] All-optical logic gates using optical input and output to replace electronic logic gate circuits including electronic binary adders, binary counters, decision circuits, and data encoders are one of the development approaches of new logic gates. However, these optical logic gates are constructed based on the complex design of optical components. Therefore, although optical logic gates have a series of advantages such as good optical gain, saturated output power, and gain bandwidth, the components are expensive and bulky, and there is a non-negligible optical loss when arranging integrated optical components due to the straight-line propagation of light, which forms a considerable obstacle to the production of high-integration systems. Under such circumstances, logic gates combining light and electricity have become the focus of attention due to their wide bandwidth, high data transmission rate, and low cost.

[0005] Compared with logic gates constructed using unipolar current photodetectors, traditional electronic logic gates, and all-optical logic gates, the current polarity controllable photodetector can realize multiple logic functions, thereby improving integration, reducing power consumption, and improving signal accuracy.

[0006] On the other hand, the current polarity controllable photodetector can also identify the wavelength band of the incident light through the difference of the current polarity without other auxiliary means. One of the commonly used wavelength identification means is to use an interferometer to identify, that is, to achieve the effect of wavelength measurement and identification according to the interference effect of the light wave. Although the interferometer has the advantages of high precision and high wavelength identification capability, it needs to arrange a complex optical path and has a higher requirement for the stability of the environment.

[0007] If the wavelength identification is performed by using a semiconductor photodetector, generally, photodetectors corresponding to different wavelength bands are needed to be used for detection to identify respectively. The photodetector can also be configured with an optical filter for wavelength identification, that is, by selectively transmitting or reflecting light signals of specific wavelengths, selective measurement of the wavelength is realized. Such a filter is usually composed of a series of optical elements with different transmission characteristics, such as an interference filter, a multilayer film filter, etc. By selecting different filter combinations, different wavelength light signals can be identified. However, the configuration of the optical filter not only causes the loss of the photoelectric conversion efficiency of the photodetector, but also significantly increases the structural complexity of the device and the system.

[0008] Therefore, it is of great significance to develop a current polarity controllable semiconductor photodetector with simple structure and manufacturing process, small size, easy integration and high reliability for the development of high-performance, miniaturized and highly integrated photologic gates and wavelength identification photodetectors. SUMMARY

[0009] The present application aims to provide a new type of current polarity controllable semiconductor photodetector with simple structure and manufacturing process, miniaturization and easy integration, which can not only realize a single photodetector multifunctional logic gate, but also realize the identification of dual-wavelength light or the high-gain detection of dual-wavelength light.

[0010] The technical scheme adopted by the present application is to provide a current polarity controllable semiconductor photodetector, wherein the photodetector adopts a group III nitride material, and the photodetector comprises a substrate and an active layer, the active layer comprises an epitaxial layer and a metal contact electrode, and the epitaxial layer comprises, in the growth order from bottom to top, a lower contact layer, a lower polarization layer, an upper polarization layer and an upper contact layer; the metal contact electrode comprises a lower contact electrode deposited on the lower contact layer and an upper contact electrode deposited on the upper contact layer; the lower polarization layer and the upper polarization layer are heterostructures, and the band gap of the lower polarization layer can be greater than or less than the band gap of the upper polarization layer; positive polarization charges or negative polarization charges can be accumulated on the contact interface of the lower polarization layer and the upper polarization layer due to the semiconductor polarization effect, and the absolute value of the heterojunction barrier formed at the contact interface of the lower polarization layer and the upper polarization layer is greater than 0.3eV.

[0011] The working principle of the current polarity controllable semiconductor photodetector is that, under the influence of the internal polarization effect in the epitaxial layer, which includes spontaneous polarization and piezoelectric polarization effect, negative or positive polarization charges will accumulate at the interface of the lower and upper polarization layers, thereby increasing or decreasing the potential energy of the heterojunction interface, forming depletion regions on both sides of the heterojunction interface, and generating two back-to-back connected built-in electric field regions that form heterojunction barriers for electrons or holes. We define the lower contact electrode as the ground terminal and the upper contact electrode as the bias voltage application terminal. Regardless of the positive or negative bias voltage applied, the depletion regions on both sides of the barrier will form one that is forward-biased and the other that is reverse-biased, i.e., the heterojunction barrier hinders the passage of most carriers. In the case where the incident light energy is lower than the band gap width of the upper and lower polarization layers, the photodetector will be in a low-conducting (current) state due to the blocking of the heterojunction barrier.

[0012] In the case of accumulating negative polarization charges at the heterojunction interface and back incidence of incident light, under zero bias or micro bias, when the photodetector is irradiated by light with photon energy greater than the band gap of the upper polarization layer and less than the band gap of the lower polarization layer, the incident light passes through the lower polarization layer and is absorbed in the upper polarization layer to excite electron-hole pairs. Since the built-in electric field in the upper polarization layer is dominant, the direction of the total current and the direction of the built-in electric field in the upper polarization layer remain consistent; when the photodetector is irradiated by light with photon energy greater than the band gap of the lower polarization layer, the incident light is absorbed in the lower polarization layer to excite electron-hole pairs, and since the built-in electric field in the lower polarization layer is greater than the applied electric field, the direction of the total current formed is also consistent with the direction of the built-in electric field in the lower polarization layer. Since the directions of the built-in electric fields in the lower polarization layer and the upper polarization layer are opposite, the device will form currents with different directions when irradiated by light with different wave bands. Thus, for a photodetector with appropriate upper and lower polarization layer structure parameters (layer thickness and carrier concentration), by using incident light with different wave bands and light intensity, and further by adjusting the bias to cooperate, logic gate operations such as AND gate and OR gate can be realized. On the other hand, for unknown incident light signals, the wave band can be identified according to the direction of the current generated by the photodetector under light incidence. If positive polarization charges accumulate at the heterojunction interface, the working principle of the photodetector remains basically the same as above, except that the current transport is dominated by the majority carrier photoholes. In addition, a larger positive bias can be applied to the upper or lower contact electrode alternately to expand the depletion region on one side of the upper contact electrode layer and the upper polarization layer, or the lower contact electrode layer and the lower polarization layer, while the depletion region on the other side of the heterojunction interface shrinks. Photoholes accumulate at the heterojunction interface, reducing the interface barrier, thereby inducing photoelectric gain due to the photoelectrons and holes generated in the depletion region of the upper contact electrode / polarization layer or the lower contact electrode / polarization layer, realizing double-wave band gain detection corresponding to the wave bands of the upper polarization or lower polarization layer band gap. The photodetector of the technical solution can cover the deep ultraviolet to near infrared wave band corresponding to the band gap of the group III nitride material, has the characteristics of simple structure and high sensitivity; as a light-controlled logic device, it can accurately realize multifunctional logic operation, and has the beneficial effects of wide wavelength recognition range and high application potential.

[0013] Preferably, the lattice structure of the group III nitride material is a wurtzite structure, and the material has piezoelectric polarization and spontaneous polarization effects, including GaN, AlN, Al x Ga 1-x N, In x Ga 1-x N, Al x In 1-x N, Al x In y Ga1-x-y N material, where 0 < x < 1, 0 < y < 1.

[0014] Preferably, the lower polarization layer and the upper polarization layer can be a multi-layer hetero-junction structure.

[0015] Preferably, the lower polarization layer and the lower contact layer can be a hetero-material with different composition ratio, and a buffer layer can be inserted between the lower contact layer and the lower polarization layer, the composition of the buffer layer being a linear or non-linear gradient of the composition ratio between the lower polarization layer and the lower contact layer.

[0016] Preferably, the upper polarization layer and the upper contact layer can be a hetero-material with different composition ratio, and a buffer layer can be inserted between the upper contact layer and the upper polarization layer, the composition of the buffer layer being a linear or non-linear gradient of the composition ratio between the upper polarization layer and the upper contact layer.

[0017] Preferably, the lower polarization layer and the upper polarization layer can be a hetero-material with different composition ratio, and a buffer layer can be inserted between the lower polarization layer and the upper polarization layer, the composition of the buffer layer being a linear or non-linear gradient of the composition ratio between the lower polarization layer and the upper polarization layer.

[0018] Preferably, the lower polarization layer and the upper polarization layer can be a III-V nitride semiconductor material with a metal-polar surface; further preferably, the III-V nitride material is grown on a Ga(Al, In) surface, and is a weak n-type lightly doped layer or an unintentionally doped layer with an electron concentration less than 3 x 1016cm-3. 17 -3 .

[0019] Preferably, the lower polarization layer and the upper polarization layer can be a III-V nitride semiconductor material with a non-metal-polar surface; further preferably, the III-V nitride material is grown on an N surface, and is a weak p-type lightly doped layer or an unintentionally doped layer with a hole concentration less than 3 x 1016cm-3. 17 -3 .

[0020] Preferably, if the semiconductor photodetector is used in a normal incidence mode, the thickness of the upper polarization layer is less than 100 nm, and the thickness of the lower polarization layer is greater than 30 nm.

[0021] Preferably, if the semiconductor photodetector is used in a back incidence mode, the thickness of the upper polarization layer is greater than 20 nm, and the thickness of the lower polarization layer is less than 500 nm.

[0022] Preferably, the lower contact layer has a band gap greater than or equal to the band gap of the lower polarization layer, and a majority carrier concentration greater than 1 x 1016cm-3. 17 -3 .

[0023] ​​​Preferably, the upper contact layer has a thickness less than 300 nm and a majority carrier concentration greater than 1*10 17 cm -3 .

[0024] Preferably, the lower contact electrode, the upper contact electrode and the lower contact layer, the upper contact layer form an ohmic contact. The metal deposited for the lower contact electrode and the upper contact electrode can be a metal stack Ti / Al / Ni / Au or V / Al / V / Au, and the thickness can be 15 / 80 / 20 / 60 nm.

[0025] Preferably, the device for implementing logic gate operation, waveband identification or dual waveband gain detection prepared by the current polarity controllable semiconductor photodetector further comprises a substrate. The substrate is prepared or supports the required substrate material for the epitaxial structure on the device. Optionally, a nucleation layer for nucleation grown on the substrate and / or other transition layers required for the implementation of the structure are arranged between the substrate and the active layer.

[0026] Another object of the present application is to provide a photologic gate device, which selects the current polarity controllable semiconductor photodetector as provided in the technical solution, applies a certain bias voltage on the upper contact electrode or the lower contact electrode, irradiates the photologic gate device with two incident lights of the waveband corresponding to the band gap of the upper polarization layer and the lower polarization layer, and forms the photologic gate according to the size of the output current. The absolute value of the applied bias voltage is not greater than 20 V.

[0027] Preferably, the photologic gate comprises an OR gate, an AND gate, a NOT gate, an NOR gate, an NAND gate, an XOR gate, or an XNOR gate.

[0028] Another object of the present application is to provide a waveband identification device, which selects the current polarity controllable semiconductor photodetector as provided in the technical solution, applies a certain bias voltage on the upper contact electrode or the lower contact electrode when the waveband identification device is irradiated with an unknown light beam, and identifies the waveband range of the unknown light beam according to the direction of the output current. The absolute value of the applied bias voltage is not greater than 10 V.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] (1) The application provides a current polarity controllable semiconductor photoelectric detector. The strong polarization effect of the III-nitride semiconductor material is utilized. A heterojunction barrier with an interface double-side depletion layer is formed at a heterojunction interface. Under a specific bias range, the device is irradiated with light of a wave band corresponding to the band gap of the lower polarization layer and the upper polarization layer. A response current with opposite or same direction is formed. Thus, the photoelectric detector provided by the application can control the current polarity according to the bias and the incident light. Further, various detection functions can be realized by controlling the current polarity of the photoelectric detector. Moreover, the current polarity controllable semiconductor photoelectric detector and the device provided with the same have simple structure, and the process can be realized by using standard semiconductor process.

[0031] (2) The application provides a novel photoelectric logic gate. Various logic operations can be realized by a single device by adjusting the incident light intensity and the bias. The speed is fast, and the integration degree is high.

[0032] (3) The application provides a wave band identification device. The III-nitride material is used as the layer material of the device. The upper and lower polarization layers can be constructed according to different ternary and quaternary III-nitride materials. Thus, different wave bands with important applications from near infrared to deep ultraviolet can be covered. The wave band can be clearly distinguished by the current polarity. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 FIG. 1 is a structure schematic diagram of the current polarity controllable semiconductor photoelectric detector of the application.

[0034] Figure 2 FIG. 2 is a structure schematic diagram of the embodiment 2 of the application.

[0035] Figure 3 FIG. 3 is a test result diagram of the embodiment 2 of the application.

[0036] Figure 4 FIG. 4 is a structure schematic diagram of the embodiment 3 of the application.

[0037] Figure 5 FIG. 5 is a structure schematic diagram of the embodiment 4 of the application.

[0038] Figure 6 FIG. 6 is a test result diagram of the embodiment 4 of the application. DETAILED DESCRIPTION

[0039] The drawings of the application are only used for exemplary description, and cannot be understood as the limitation of the application. In order to better illustrate the following embodiments, some components in the drawings can be omitted, enlarged or reduced, and do not represent the size of the actual product. It is understandable for those skilled in the art that some well-known structures and their descriptions in the drawings can be omitted.

[0040] Embodiment 1

[0041] AsFigure 1 The embodiment aims to provide a semiconductor photodetector with controllable current polarity, wherein the photodetector adopts a group III nitride material, and the photodetector comprises a substrate and an active layer, the active layer comprises an epitaxial layer and a metal contact electrode, the epitaxial layer is a multilayer structure, and the epitaxial layer comprises, in a growth order from bottom to top, a lower contact layer 101, a lower polarization layer 102, an upper polarization layer 103, and an upper contact layer 104; the metal contact electrode comprises a lower contact electrode 105 deposited on the lower contact layer 101, and an upper contact electrode 106 deposited on the upper contact layer 104; the lower polarization layer and the upper polarization layer are a heterostructure, and the band gap of the lower polarization layer can be greater than or less than the band gap of the upper polarization layer; the contact interface between the lower polarization layer and the upper polarization layer can accumulate positive polarization charges or negative polarization charges due to a semiconductor polarization effect, and the absolute value of a heterojunction barrier formed at the contact interface between the lower polarization layer and the upper polarization layer is greater than 0.3 eV.

[0042] The group III nitride material has a wurtzite structure, and the material has piezoelectric polarization and spontaneous polarization effects, and the group III nitride material comprises GaN, AlN, Al x Ga 1-x N, In x Ga 1-x N, Al x In 1-x N, Al x In y Ga 1-x-y N, and 0 < x < 1 and 0 < y < 1.

[0043] Preferably, the lower polarization layer and the upper polarization layer are Ga (Al, In) -plane grown group III nitride materials, and are weak n-type lightly doped layers or unintentionally doped layers, and the electron concentration of the layers is less than 3 × 10 17 cm -3 ; or, the lower polarization layer and the upper polarization layer are N-plane grown group III nitride materials, and are weak p-type lightly doped layers or unintentionally doped layers, and the hole concentration of the layers is less than 3 × 10 17 cm -3 .

[0044] Preferably, the lower polarization layer and the upper polarization layer can be a multilayer heterojunction structure.

[0045] Preferably, the lower polarization layer and the lower contact layer can be heterogeneous materials with different composition ratios. A buffer layer can be inserted between the lower contact layer and the lower polarization layer, and the composition of the buffer layer is a linear or non-linear gradient of the composition ratio between the lower polarization layer and the lower contact layer. And / or, the upper polarization layer and the upper contact layer can be heterogeneous materials with different composition ratios. A buffer layer can be inserted between the upper contact layer and the upper polarization layer, and the composition of the buffer layer is a linear or non-linear gradient of the composition ratio between the upper polarization layer and the upper contact layer. And / or, the lower polarization layer and the upper polarization layer can be heterogeneous materials with different composition ratios. A buffer layer can be inserted between the lower polarization layer and the upper polarization layer, and the composition of the buffer layer is a linear or non-linear gradient of the composition ratio between the lower polarization layer and the upper polarization layer.

[0046] Preferably, if normal incident light is used, the thickness of the upper polarization layer of the semiconductor photodetector is less than 100 nm and the thickness of the lower polarization layer is greater than 30 nm.

[0047] Preferably, if the photodetector uses back-incident light, its upper polarization layer thickness is greater than 20 nm and its lower polarization layer thickness is less than 500 nm.

[0048] Preferably, the bandgap of the lower contact layer is greater than or equal to the bandgap of the lower polarization layer, and its majority carrier concentration is greater than 1×10⁻⁶. 17 cm -3 .

[0049] Preferably, the thickness of the upper contact layer is less than 300 nm, and its majority carrier concentration is greater than 1 × 10⁻⁶. 17 cm -3 Preferably, the lower contact electrode and the upper contact electrode form an ohmic contact with the lower contact layer and the upper contact layer. The metal deposited on the lower contact electrode and the upper contact electrode can be a metal stack Ti / Al / Ni / Au or V / Al / V / Au, with a thickness of 15 / 80 / 20 / 60 nm.

[0050] Example 2

[0051] like Figure 2 As shown, this embodiment aims to provide an optoelectronic logic gate device capable of implementing logic including optically controlled OR gates, AND gates, NOT gates, NOR gates, NAND gates, XOR gates, and XNOR gates. The optoelectronic logic gate device in this embodiment uses a semiconductor photodetector with controllable current polarity as provided in Embodiment 1; wherein the detection wavelength is in the UVA and UVC bands, and the light incident mode is back incidence. The device structure, from bottom to top, consists of a substrate, a nucleation layer, a transition layer, a lower contact layer 201, a lower buffer layer 202, a lower polarization layer 203, an upper polarization layer 204, an upper contact layer 205, a lower contact electrode 206, and an upper contact electrode 207.

[0052] The substrate is a double-side polished c-plane sapphire substrate with a wurtzite structure, and its crystal plane orientation is

[0001] .

[0053] The nucleation layer is an AlN layer grown on the substrate, with a thickness of 1000 nm.

[0054] The transition layer is a high-concentration doped n-type Al 0.6～1.0 GaN layer gradually changing from AlN to Al 0.6 GaN from bottom to top, and the composition change can be linear or nonlinear, with an electron concentration of 2x1018cm 18 -3cm -3 and a thickness of 100 nm.

[0055] The lower contact layer 201 is a high-concentration doped n-type Al 0.6 GaN layer with an electron concentration of 3x1018cm 18 -3cm -3 and a thickness of 300 nm.

[0056] The lower buffer layer 202 is an unintentionally doped Al 0.4～0.6 GaN layer, with Al 0.6 GaN gradually changing to Al 0.4 GaN from bottom to top, and the composition change can be linear or nonlinear, with an electron concentration of 5x1018cm 16 -2cm -3 and a thickness of 35 nm.

[0057] The lower polarization layer 203 is an unintentionally doped Al 0.4 GaN layer with an electron concentration of 1x1018cm 16 -2cm -3 and a thickness of 120 nm.

[0058] The upper polarization layer 204 is an unintentionally doped GaN layer with an electron concentration of 3x1018cm 16 -2cm -3 and a thickness of 120 nm.

[0059] The upper contact layer 205 is a high-concentration doped n-type GaN layer with an electron concentration of 2x1018cm 18 -2cm -3 and a thickness of 100 nm.

[0060] The lower contact electrode 206 and the upper contact electrode 207 are Ti / Au / Ni / Au metal stacks deposited on the lower contact layer and the upper contact layer, with a thickness of 15 / 80 / 20 / 60 nm.

[0061] In this embodiment, due to the polarization effect, the upper polarization layer (uid-GaN layer), the lower polarization layer (uid-Al 0.4The GaN layer interface accumulates positively charged negative charges, forming a heterojunction barrier. When the UVA and UVC wavelengths are not detected, the heterojunction barrier hinders electron flow, resulting in low dark current. Under a certain positive bias, when the device is irradiated with light (UVA) corresponding to the bandgap of the upper polarization layer (uid-GaN layer), the direction of the current is from the upper contact electrode to the lower contact electrode; when the lower polarization layer (uid-Al) is used... 0.4 The light (UVC) irradiation device corresponding to the band gap of the GaN layer forms a current direction from the upper contact electrode to the lower contact electrode, and its current direction is the same as the former. By setting the power of the two incident light beams and the high and low level boundary points of the output current, optical control logic gates such as OR gate, AND gate, NOT gate, NOR gate, NAND gate, XOR gate, and XNOR gate can be formed according to the magnitude of the current formed after the beam is incident.

[0062] Taking the formation of an AND gate device as an example, such as Figure 3 As shown, under a positive bias of 1.7V, an illumination intensity of 428μW / cm² was used. 2 When the device is irradiated with UVA, the UVA light signal is "1", and the output current of the device is 3nA. The illumination intensity is 24.1 μW / cm². 2 When the UVC irradiates the device, the UVC light signal is "1", and the output current of the device is 3nA. If the reference for high and low levels is set to 5nA, then when both the UVA light signal and the UVC light signal are "1", the logic operation result is "1".

[0063] Example 3

[0064] like Figure 4 As shown, this embodiment aims to provide an optoelectronic logic gate device capable of implementing logic including optically controlled OR gates, AND gates, NOT gates, NOR gates, NAND gates, XOR gates, and XNOR gates. The optoelectronic logic gate device in this embodiment uses a semiconductor photodetector with controllable current polarity as provided in Embodiment 1. The difference between this embodiment and Embodiment 2 is that the detection wavelength is in the violet and UVA bands, and the light incident method is back incidence. The device structure, from bottom to top, consists of a substrate layer, a lower contact layer 301, a lower polarization layer 302, an upper polarization layer 303, an upper contact layer 304, a lower contact electrode 305, and an upper contact electrode 306.

[0065] The substrate material is GaN or c-plane sapphire with a wurtzite lattice structure and its crystal plane orientation is

[0001] .

[0066] The lower contact layer 301 is a highly doped n-type GaN layer with an electron concentration of 1.5 × 10⁻⁶. 18 cm -3 The thickness is 200nm.

[0067] The lower polarization layer 302 is an unintentionally doped GaN layer with an electron concentration of 1×10⁻⁶. 16 cm -3 The thickness is 300nm.

[0068] The upper polarization layer 303 is unintentionally doped with In. 0.2 GaN layer, electron concentration of 2×10 15 cm -3 The thickness is 110nm.

[0069] The upper contact layer 304 is a highly doped n-type In. 0.2 GaN layer, electron concentration of 2×10 18 cm -3 The thickness is 20nm.

[0070] The lower contact electrode 305 and the upper contact electrode 306 are Ti / Au / Ni / Au metal stacks deposited on the lower contact layer and the upper contact layer, with thicknesses of 15 / 80 / 20 / 60nm.

[0071] In this implementation case, under a certain bias voltage, the device is irradiated with light of the corresponding power in the violet and UVA bands. The high and low level boundary points can be set according to the magnitude of the current, thereby forming corresponding optically controlled OR gate, AND gate, NOT gate, NOR gate, NAND gate, XOR gate, XNOR gate, and other logic gates.

[0072] Example 4

[0073] like Figure 5 As shown, this embodiment aims to provide a band identification device. The optoelectronic logic gate device in this embodiment is a semiconductor photodetector with controllable current polarity, as provided in Embodiment 1. The identification bands are the violet band and the UVA band, and the light incident mode is back incidence. The device structure, from bottom to top, consists of a substrate, a transition layer, a lower contact layer 401, a lower polarization layer 402, an upper polarization layer 403, an upper contact layer 404, a lower contact electrode 405, and an upper contact electrode 406.

[0074] The substrate is a double-polished c-plane sapphire substrate with a wurtzite lattice structure and its crystal orientation is

[0001] .

[0075] The transition layer, from bottom to top, consists of a 20 nm thick low-temperature AlN nucleation layer and a 1 μm thick unintentionally doped Al layer. 0.05 GaN layer.

[0076] The lower contact layer 401 includes, from bottom to top, highly doped n-type Al 0.05 GaN layer (electron concentration of 1.5 × 10⁻⁶) 18 cm -3(300 nm thick) and n-type Al with Al composition x gradually changing from 0.05 to 0. x GaN layer (electron concentration of 1.0 × 10⁻⁶) 18 cm -3 (Thickness is 30nm).

[0077] The lower polarization layer 402 is an unintentionally doped GaN layer with an electron concentration of 8 × 10⁻⁶. 16 cm -3 The thickness is 200nm.

[0078] The upper polarization layer 403 is unintentionally doped with In. 0.2 GaN layer, electron concentration of 2×10 17 cm -3 The thickness is 100nm.

[0079] The upper contact layer 404 is a highly doped n-type In. 0.2 GaN layer, electron concentration of 2×10 18 cm -3 The thickness is 20nm.

[0080] The lower contact electrode 405 and the upper contact electrode 406 are Ti / Au / Ni / Au metal stacks deposited on the lower contact layer and the upper contact layer, with thicknesses of 15 / 80 / 20 / 60nm.

[0081] In this implementation, back-incidence detection is used. Because the bandgap of the upper polarization layer is smaller than that of the lower polarization layer, back-incidence effectively reduces the absorption of light of the corresponding wavelength by the upper material. Under a weak bias, when using uid-In... 0.2 When the detector is illuminated with light (violet light) corresponding to the bandgap of the GaN layer (upper polarization layer), the direction of the current is from the upper contact electrode to the lower contact electrode. When the detector is illuminated with light (UVA) corresponding to the bandgap of the uid-GaN layer (lower polarization layer), the direction of the current is from the lower contact electrode to the upper contact electrode, which is opposite to the former. Therefore, the incident light band can be determined based on the direction of the current. Figure 6 As shown, when a positive bias voltage of 0.43V is applied to the band identification device, when the device is irradiated with incident light of wavelength 400nm, the current output by the device is in the positive direction, that is, from the upper contact electrode to the lower contact electrode, and it is identified as the violet band; when the device is irradiated with incident light of wavelength 355nm, the current output by the device is in the negative direction, that is, from the lower contact electrode to the upper contact electrode, and it is identified as the UVA ultraviolet band.

[0082] On the other hand, for the wave band identification device provided in the embodiment, when a positive voltage greater than 1.5V is applied to the upper contact electrode 406 or the lower contact electrode 405 alternately, a response photocurrent with high photoelectric gain corresponding to the wave band corresponding to the band gap of the upper polarization layer 403 or the lower polarization layer 402 can be obtained, thereby realizing high-gain dual-wave band detection.

[0083] Obviously, the above-mentioned embodiments of the present application are only examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the specific embodiments of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A semiconductor photodetector with controllable current polarity, characterized in that, The photodetector uses a group III nitride material, and its active layer includes an epitaxial layer and a metal contact electrode. The epitaxial layer is grown in the following order from bottom to top: lower contact layer, lower polarization layer, upper polarization layer and upper contact layer. The metal contact electrode includes a lower contact electrode deposited on a lower contact layer and an upper contact electrode deposited on an upper contact layer; The lower polarization layer and the upper polarization layer are heterogeneous structures, and the band gap of the lower polarization layer can be greater than or less than the band gap of the upper polarization layer. Positive or negative polarization charges accumulate at the contact interface between the lower and upper polarization layers, and the absolute value of the heterojunction barrier formed at the contact interface between the lower and upper polarization layers is greater than 0.3 eV. The lower and upper polarization layers are group III nitride semiconductor materials with metallic polar crystal planes, and are lightly doped or unintentionally doped layers of weak n-layer type, with an electron concentration of less than 3 × 10⁻⁶. 17 cm -3 The metal polar crystal plane group III nitride semiconductor material is a group III nitride semiconductor material grown on one or more of Ga, Al, and In planes. Alternatively, the lower polarization layer and the upper polarization layer are group III nitride semiconductor materials with non-metallic polar crystal planes, and are weakly p-layer type lightly doped layers or unintentionally doped layers with a hole concentration of less than 3 × 10⁻⁶. 17 cm -3 The non-metallic polar crystal plane group III nitride semiconductor material is a group III nitride semiconductor material grown on the N-plane.

2. The semiconductor photodetector with controllable current polarity according to claim 1, characterized in that, The epitaxial layer further includes a buffer layer, which is disposed between the lower contact layer and the lower polarization layer, and / or between the lower polarization layer and the upper polarization layer, and / or between the upper polarization layer and the upper contact layer; The two adjacent layers of the buffer layer are heterogeneous materials with different component ratios. The components of the buffer layer change linearly or non-linearly between the component ratios of the adjacent upper and lower layers of the buffer layer.

3. The semiconductor photodetector with controllable current polarity according to any one of claims 1-2, characterized in that, When the photodetector uses normal incident light, its upper polarization layer thickness is less than 100 nm and its lower polarization layer thickness is greater than 30 nm. When the photodetector uses back-incident light, its upper polarization layer thickness is greater than 20 nm and its lower polarization layer thickness is less than 500 nm.

4. The semiconductor photodetector with controllable current polarity according to any one of claims 1-2, characterized in that, The bandgap of the lower contact layer is not less than the bandgap of the lower polarization layer, and its majority carrier concentration is greater than 1×10⁻⁶. 17 cm -3 ; The thickness of the upper contact layer is less than 300 nm, and its majority carrier concentration is greater than 1 × 10⁻⁶. 17 cm -3 .

5. The semiconductor photodetector with controllable current polarity according to any one of claims 1-2, characterized in that, The lower contact electrode forms an ohmic contact with the lower contact layer, and the upper contact electrode forms an ohmic contact with the upper contact layer.

6. A photoelectric logic gate device, characterized in that, The optoelectronic logic gate device is selected as a semiconductor photodetector with controllable current polarity as described in any one of claims 1-5. By applying a certain bias voltage to the upper contact electrode or the lower contact electrode, two incident beams of light corresponding to the band gaps of the upper polarization layer and the lower polarization layer are respectively used to irradiate the optoelectronic logic gate device, and the optoelectronic logic gate is formed according to the magnitude of the output current. The absolute value of the applied bias voltage is no greater than 20V.

7. The optoelectronic logic gate device according to claim 6, characterized in that, The optoelectronic logic gates include OR gate, AND gate, NOT gate, NOR gate, NAND gate, XOR gate, and XNOR gate.

8. A band identification device, characterized in that, The band identification device is a semiconductor photodetector with controllable current polarity as described in any one of claims 1-5. When the band identification device is irradiated with an unknown light beam, the band range of the unknown light beam is identified by applying a certain bias voltage to the upper or lower contact electrode and based on the direction of the output current. The absolute value of the bias voltage applied to the upper or lower contact electrode is not greater than 10V.

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