Dual-heterojunction GaN HEMT (High Electron Mobility Transistor) ultraviolet detector based on dual-gate regulation
By utilizing the synergistic effect of the front and back gates, the dual heterojunction GaN HEMT ultraviolet detector optimizes the dark and light state performance, solving the problems of large dark current and low photogenerated carrier separation efficiency of traditional GaN-based ultraviolet detectors, and achieving high sensitivity and fast response detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGNAN UNIV
- Filing Date
- 2025-12-31
- Publication Date
- 2026-05-15
AI Technical Summary
Traditional GaN-based ultraviolet detectors suffer from problems such as large dark current, low photogenerated carrier separation efficiency, and slow response speed, making it difficult to achieve high sensitivity, low noise, and fast response characteristics.
A dual heterojunction GaN HEMT ultraviolet detector based on dual-gate control is adopted. The dark-state and light-state performance are optimized by the synergistic effect of the front gate and the back gate, respectively. The band tilt is controlled by the synergistic effect of the applied electric field and the polarization field to form two-dimensional electron gas and two-dimensional hole gas channels, and the dark current and photocurrent are independently controlled.
It significantly improves the separation efficiency and transmission speed of photogenerated carriers, enhances the sensitivity and response speed of the detector, and achieves effective suppression of dark current and enhancement of photocurrent.
Smart Images
Figure CN122054710A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ultraviolet detectors, and in particular to a dual heterojunction GaN HEMT ultraviolet detector based on dual-gate control. Background Technology
[0002] Ultraviolet (UV) detectors have significant applications in environmental monitoring, flame detection, and military reconnaissance. Traditional GaN-based UV detectors suffer from problems such as high dark current, low photogenerated carrier separation efficiency, and slow response speed. In existing technologies, single-gate HEMT devices have limitations in carrier manipulation, making it difficult to simultaneously achieve effective suppression of dark current and enhancement of photocurrent. Especially in UV detection applications, devices require high sensitivity, low noise, and fast response. Therefore, there is an urgent need for a novel UV detector structure capable of optimizing dark and light state performance through independent dual-gate control. Summary of the Invention
[0003] Therefore, the technical problem to be solved by the present invention is: low sensitivity.
[0004] The above-mentioned technical problems are solved by the following technical solution: The present invention proposes a dual heterojunction GaN HEMT ultraviolet detector based on dual gate control, which includes a device, wherein the device includes a substrate, a buffer layer, a bottom aluminum gallium nitride alloy layer, a gallium nitride layer and a top aluminum gallium nitride alloy layer arranged sequentially from bottom to top; The ultraviolet detector also includes a source, a drain, a front gate, and a back gate disposed on the device; The top aluminum gallium nitride alloy layer and the gallium nitride layer form a first heterojunction and form a two-dimensional electron gas conductive channel. The bottom aluminum gallium nitride alloy layer and the gallium nitride layer form a second heterojunction and form a two-dimensional hole gas channel. The back gate controls the band tilt of the gallium nitride layer by coordinating the applied electric field and the polarization field. The front gate suppresses dark current by controlling the concentration of two-dimensional electron gas.
[0005] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention: both the bottom aluminum gallium nitride alloy layer and the top aluminum gallium nitride alloy layer are Al x Ga 1-x There are N layers, where the value of x ranges from 0 to x and from 1 to 0.
[0006] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention, the value of x is 0.7.
[0007] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention: the front gate is disposed above the top aluminum gallium nitride alloy layer.
[0008] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention, the thickness of the buffer layer is 0.1 to 5 μm.
[0009] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention: the thickness of the bottom aluminum gallium nitride alloy layer and the top aluminum gallium nitride alloy layer are both 0.05 to 2 μm.
[0010] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention, the thickness of the gallium nitride layer is 0.1 to 3 μm.
[0011] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention: the source, drain, front gate and back gate are made of one of Ti, Al, Ni and Au.
[0012] This invention also proposes a fabrication method for the above-mentioned dual-gate controlled double heterojunction GaNHEMT ultraviolet detector; the steps are as follows: A buffer layer, a bottom aluminum gallium nitride alloy layer, a gallium nitride layer, and a top aluminum gallium nitride alloy layer are grown sequentially on the substrate. Fabrication of the back gate; The source, drain, and front gate are fabricated on the top aluminum gallium nitride alloy layer; The growth is performed using a metal-organic chemical vapor deposition method.
[0013] In a preferred embodiment of the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector of the present invention: the source and drain are fabricated by sputter magnetron sputtering and then annealed at a temperature of 500-850°C for 30 seconds to 10 minutes.
[0014] The beneficial effects of this invention are as follows: the front gate is specifically used for dark current suppression, and the back gate is specifically used for photocurrent enhancement, achieving separate optimization of dark-state and light-state performance. The synergistic working mechanism—the external electric field of the back gate and the inherent polarization field of the material—synergistically enhances the separation efficiency of photogenerated carriers. Through dual-gate modulation, the light-dark output characteristic ratio of the device is significantly improved, enhancing detection sensitivity. A double heterojunction structure is employed, simultaneously forming 2DEG and 2DHG channels, providing independent transport paths for photogenerated electrons and holes. Based on mature GaN HEMT fabrication technology, it possesses good manufacturability and reliability. Attached Figure Description
[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein: Figure 1 A schematic diagram of a dual heterojunction GaN HEMT ultraviolet detector based on dual-gate control is shown. Detailed Implementation
[0016] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0017] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.
[0018] Reference Figure 1 This embodiment provides a dual heterojunction GaN HEMT ultraviolet detector based on dual gate control, including a device. The device adopts a bottom-up layered stacking design, and the device includes a substrate 1, a buffer layer 2, a bottom aluminum gallium nitride alloy layer 3, a gallium nitride layer 4, and a top aluminum gallium nitride alloy layer 5 arranged sequentially from bottom to top. The stacking sequence is based on the lattice matching characteristics and optoelectronic functions of the materials. The substrate 1 serves as the supporting foundation for the entire device, providing stable mechanical support and growth substrate for the growth of subsequent functional layers. The buffer layer 2 is disposed between the substrate 1 and the bottom aluminum gallium nitride alloy layer 3. Its core function is to alleviate the lattice mismatch and thermal mismatch between the substrate 1 and the subsequent nitride layer, reduce the defect density at the heterojunction, and improve the crystal quality of the subsequent functional layers. The bottom aluminum gallium nitride alloy layer 3, gallium nitride layer 4, and top aluminum gallium nitride alloy layer 5 constitute the core functional area of the detector. Among them, gallium nitride layer 4 serves as the core layer for ultraviolet light absorption. Due to its wide bandgap characteristics, it can efficiently absorb ultraviolet light and generate photogenerated electron-hole pairs. The top aluminum gallium nitride alloy layer 5 and the bottom aluminum gallium nitride alloy layer 3 are located on the upper and lower sides of the gallium nitride layer 4, respectively, forming a symmetrical double heterojunction structure, which provides an energy gradient for the separation and directional transport of charge carriers.
[0019] The ultraviolet detector also includes a source electrode 6, a drain electrode 7, a front gate electrode 8, and a back gate electrode 9 disposed on the device; the four electrodes ensure the photoelectric conversion and signal output of the device, wherein the source electrode 6 and the drain electrode 7 serve as the input and output terminals of the charge carriers, forming a current transmission path, which is used to collect the separated and transmitted photogenerated charge carriers and convert the photoelectric signal into a detectable electrical signal. The front gate 8 and the back gate 9 serve as control electrodes, which precisely control the dark current suppression and carrier separation efficiency, respectively. The two work together to optimize the device performance.
[0020] The top aluminum gallium nitride alloy layer 5 and gallium nitride layer 4 form a first heterojunction due to the difference in their material band gaps. The polarization discontinuity at the heterojunction interface induces the formation of a two-dimensional electron gas conductive channel 10. This channel has high electron mobility characteristics, enabling rapid transmission of photogenerated electrons and reducing recombination losses during transmission. The bottom aluminum gallium nitride alloy layer 3 and gallium nitride layer 4 also form a second heterojunction due to the difference in bandgap width, which correspondingly induces the formation of a two-dimensional hole gas channel 11. This channel is specifically used to transport photogenerated holes and forms a complementary carrier transport path with the two-dimensional electron gas conductive channel 10, thus avoiding the recombination of electrons and holes. The double heterojunction structure, composed of the first heterojunction and the second heterojunction, confines photogenerated electrons and holes in their respective transport channels through energy barriers on the upper and lower sides, significantly improving the carrier separation efficiency and transport speed.
[0021] The core control mechanism of the back gate 9 is to form a synergistic effect between the external electric field and the polarization field inside the device, thereby controlling the band tilt of the gallium nitride layer 4. The optimization of the band tilt can enhance the internal electric field strength, provide greater separation force for photogenerated electron-hole pairs, accelerate the migration of charge carriers to their respective channels, reduce the recombination probability, and improve the response speed and responsivity of the detector. The front gate 8 suppresses dark current by regulating the concentration of the two-dimensional electron gas. Dark current is the leakage current generated by the detector under no light conditions, mainly caused by factors such as thermally excited charge carriers. By regulating the voltage of the front gate 8, the concentration of the two-dimensional electron gas can be precisely controlled, reducing the carrier transport efficiency under no light conditions, thereby suppressing dark current and improving the signal-to-noise ratio and detection accuracy of the detector.
[0022] As an optional embodiment, the bottom aluminum gallium nitride alloy layer 3 and the top aluminum gallium nitride alloy layer 5 are specifically made of Al x Ga 1-x The N-ternary alloy material, based on the tunable composition of ternary alloys, can optimize the band gap and lattice constant of the material by precisely controlling the mole fraction x of Al, thereby adapting to the formation requirements and carrier transport characteristics of double heterojunctions.
[0023] Alx Ga 1-x The range of values for the Al component x in N is set to 0 < x < 1, which is based on a dual consideration of material physical properties and device function. When x=0, the material degenerates into pure GaN, and there is no effective bandgap difference between it and the GaN layer, making it difficult to construct a heterojunction barrier and unable to induce two-dimensional electron gas or two-dimensional hole gas channels. When x=1, the material becomes pure AlN, and its lattice mismatch with the GaN layer increases significantly, which leads to a sharp increase in the density of interface defects, disrupting the transport path of charge carriers. At the same time, the excessively high Al content also increases the difficulty of material growth and makes it easy to generate structural defects such as cracks.
[0024] Therefore, the range of values 0 < x < 1 not only ensures the band gap difference required for heterojunction formation, but also balances the lattice matching degree and crystal growth quality by reasonably selecting the x value, thus providing a basis for the stable operation of the double heterojunction structure.
[0025] Within the aforementioned value range, setting x to 0.7 is the optimal solution after performance optimization. When x = 0.7, Al 0.7 Ga 0.3 The bandgap of the Ni material and the GaN layer form an ideal difference, enabling the construction of a suitable heterojunction barrier: for the top Al layer... 0.7 Ga 0.3 The first heterojunction formed by N and GaN effectively confines photogenerated electrons, inducing the formation of a high-concentration, high-mobility two-dimensional electron gas conductive channel 10; for the underlying Al... 0.7 Ga 0.3 The second heterojunction formed by N and GaN can precisely match the transport requirements of photogenerated holes, forming a stable two-dimensional hole gas channel 11.
[0026] Meanwhile, the component design with x=0.7 allows Al 0.7 Ga 0.3 With the lattice mismatch between the N and GaN layers controlled within a reasonable range, combined with the stress-relieving effect of the buffer layer 2, the interface defect density can be significantly reduced, improving crystal growth quality and ensuring carrier transport efficiency within the channels. Furthermore, the Al composition under this condition... 0.7 Ga 0.3 N also possesses excellent polarization characteristics, enabling it to form a highly efficient synergy with the external electric field of the back gate 9, enhancing the band tilt control effect of the gallium nitride layer 4, while simultaneously regulating the two-dimensional electron gas concentration and suppressing dark current for the front gate 8.
[0027] As an optional embodiment, the front gate 8 is disposed above the top aluminum gallium nitride (AGaN) layer 5. From the perspective of device structure logic, the top AGaN layer 5 and the underlying gallium nitride (GaN) layer 4 constitute the first heterojunction. This heterojunction interface is precisely the formation region of the two-dimensional electron gas (2D) conductive channel 10. The concentration of the 2D electron gas directly determines the magnitude of the dark current and also affects the transmission efficiency of photogenerated electrons. The core function of the front gate 8 is to suppress the dark current by regulating the concentration of the 2D electron gas. By placing it above the top AGaN layer 5, the gate electric field can directly act on the heterojunction interface region where the 2D electron gas is located. The accumulation or depletion state of the 2D electron gas can be quickly changed by voltage regulation, effectively reducing the carrier transmission efficiency in the absence of light, thereby suppressing the dark current.
[0028] As an optional embodiment, the thickness of the buffer layer 2 is 0.1 to 5 μm, and the thickness of the AlN buffer layer 2 is 0.1 to 5 μm. The setting of this thickness range is based on the synergistic adaptation between the core function of the buffer layer 2 and the overall performance of the device and the fabrication process, which is in line with the structural design and working principle of the detector.
[0029] The core function of the AlN buffer layer 2 is to alleviate the lattice and thermal mismatch between the sapphire substrate 1 and the subsequent AlGaN and GaN functional layers. Sapphire inherently differs from AlN and GaN in lattice constants and thermal expansion coefficients; directly growing functional layers would lead to numerous dislocations and stress concentrations at the interface, severely impacting carrier transport efficiency and device stability. Therefore, the appropriate selection of the thickness is crucial to ensuring the effective functioning of this core layer. If the thickness of the AlN buffer layer 2 is less than 0.1 μm, its mitigation effect on lattice mismatch and thermal mismatch will be greatly reduced, failing to adequately neutralize the stress between the substrate 1 and the functional layer. This will significantly increase the interface defect density, affecting the subsequent growth of the underlying Al layer. 0.7 Ga 0.3 The crystal quality of N-layer and GaN-layer will be severely affected, resulting in problems such as small grain size and increased defects. This will hinder the formation of two-dimensional electron gas and two-dimensional hole gas channels 11, reduce the separation and transport efficiency of photogenerated carriers, and ultimately lead to a decrease in detector responsivity and an increase in noise.
[0030] If the AlN buffer layer 2 thickness exceeds 5 μm, on the one hand, it will significantly increase the difficulty of the metal-organic chemical vapor deposition (MOCVD) growth process. The excessively long growth time is prone to structural defects such as cracks and pores inside the AlN layer, which will damage the structural integrity of the device. On the other hand, an excessively thick AlN layer will introduce additional stress accumulation, which is not only detrimental to the epitaxial growth of subsequent functional layers, but also increases the overall thickness and fabrication cost of the device. At the same time, it may affect the thermal conductivity of the device, leading to heat accumulation during operation and affecting the stability of the detection performance.
[0031] As an optional embodiment, the thickness of both the bottom and top aluminum gallium nitride (AGaN) alloy layers 5 is 0.05–2 μm. The core function of these layers is to form double heterojunctions with the intermediate GaN layer, thereby inducing two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) channels, and providing a stable structural basis for dual-gate control. The appropriate selection of the thickness of the 2DEG or 2DHG channels directly determines the effectiveness of the heterojunction barrier and the precision of carrier control: if the thickness is less than 0.05 μm, the AGaN alloy layer cannot form a sufficiently strong heterojunction barrier, making it difficult to effectively confine photogenerated carriers and stably induce... An excessively thin layer structure leads to insufficient barrier height, making it easy for charge carriers to overflow the channel and exacerbating recombination losses. It also weakens the polarization characteristics of the material, affecting the synergistic control effect of the applied electric field and polarization field of the back gate 9. If the thickness exceeds 2μm, on the one hand, it will significantly increase the lattice mismatch stress between the aluminum gallium nitride layer and the GaN layer, resulting in a significant increase in the interface defect density, which will destroy the integrity of the heterojunction interface and hinder the efficient transport of charge carriers. On the other hand, it will prolong the growth cycle of metal-organic chemical vapor deposition (MOCVD), increasing the process difficulty and preparation cost. Furthermore, an excessively thick aluminum gallium nitride layer may block the absorption of ultraviolet light by the GaN layer, indirectly affecting the generation efficiency of photogenerated charge carriers.
[0032] As an optional embodiment, the thickness of the gallium nitride layer 4 is 0.1–3 μm. The GaN layer serves as the core ultraviolet absorption layer of the detector, and its core function is to efficiently absorb ultraviolet light and generate photogenerated electron-hole pairs. Simultaneously, it acts as the top and bottom Al... 0.7 Ga 0.3 The N-layer and GaN-layer form a double heterojunction, providing a stable substrate and ensuring effective separation and carrier transport of the two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) channels. From a functional implementation perspective, the appropriate selection of thickness directly determines the light absorption efficiency and carrier transport effect. If the GaN layer thickness is less than 0.1 μm, the propagation path of ultraviolet light within the layer is too short, resulting in insufficient light absorption and an inability to generate a sufficient number of photogenerated electron-hole pairs. This directly leads to insufficient photocurrent in the device and a decrease in detection sensitivity. Simultaneously, an excessively thin GaN layer cannot provide enough space to support the stable formation of a double heterojunction structure, hindering the interaction between the top and bottom Al layers. 0.7 Ga 0.3 The potential barriers of the N layers can interfere with each other, affecting the independence of the 2DEG and 2DHG channels, and thus reducing carrier separation efficiency.
[0033] If the GaN layer thickness exceeds 3 μm, although the light absorption path is extended, it will cause two key problems: First, the transmission distance of photogenerated carriers in the GaN layer increases significantly. During the migration of carriers to the 2DEG or 2DHG channels, the probability of collisions with lattice defects and impurities increases dramatically, leading to increased carrier recombination loss and reducing the effective carrier utilization rate. Second, an excessively thick GaN layer increases the difficulty of the metal-organic chemical vapor deposition (MOCVD) growth process. The excessively long growth cycle is prone to stress accumulation and increased crystal defects within the layer, which damages the crystal quality of the GaN layer and also exacerbates the interaction with the surrounding Al atoms. 0.7 Ga 0.3 The lattice mismatch stress of the N-layer affects the heterojunction interface quality and weakens the effect of the back gate 9 on the band tilt of the GaN layer.
[0034] As an optional embodiment, the source 6, drain 7, front gate 8, and back gate 9 are made of one or more combinations of Ti, Al, Ni, and Au.
[0035] This invention also proposes a fabrication method for the above-mentioned dual-gate controlled double heterojunction GaNHEMT ultraviolet detector; the steps are as follows: A buffer layer 2, a bottom aluminum gallium nitride alloy layer 3, a gallium nitride layer 4, and a top aluminum gallium nitride alloy layer 5 are grown sequentially on substrate 1. Fabrication of back gate 9; Source 6, drain 7 and front gate 8 are fabricated on the top aluminum gallium nitride alloy layer 5; The growth process employs a metal-organic chemical vapor deposition method.
[0036] Source 6 and drain 7 were prepared by sputter magnetron sputtering and then annealed at a temperature of 500–850 °C for 30 seconds to 10 minutes.
[0037] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.
Claims
1. A dual-gate controlled GaN HEMT ultraviolet detector, characterized in that: The device includes a substrate (1), a buffer layer (2), a bottom aluminum gallium nitride alloy layer (3), a gallium nitride layer (4), and a top aluminum gallium nitride alloy layer (5) arranged sequentially from bottom to top. The ultraviolet detector also includes a source (6), a drain (7), a front gate (8), and a back gate (9) disposed on the device. The top aluminum gallium nitride alloy layer (5) and the gallium nitride layer (4) form a first heterojunction and form a two-dimensional electron gas conductive channel (10). The bottom aluminum gallium nitride alloy layer (3) and the gallium nitride layer (4) form a second heterojunction and form a two-dimensional hole gas channel (11). The back gate (9) controls the band tilt of the gallium nitride layer (4) through the coordinated control of the applied electric field and the polarization field. The front gate (8) suppresses dark current by controlling the concentration of two-dimensional electron gas.
2. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 1, characterized in that: Both the bottom aluminum gallium nitride alloy layer (3) and the top aluminum gallium nitride alloy layer (5) are Al x Ga 1-x There are N layers, where the value of x ranges from 0 to x and from 1 to 0.
3. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 2, characterized in that: The value of x is 0.
7.
4. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 1, characterized in that: The front gate (8) is disposed above the top aluminum gallium nitride alloy layer (5).
5. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 1, characterized in that: The thickness of the buffer layer (2) is 0.1 to 5 μm.
6. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 1, characterized in that: The thickness of both the bottom aluminum gallium nitride alloy layer (3) and the top aluminum gallium nitride alloy layer (5) is 0.05 to 2 μm.
7. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 1, characterized in that: The thickness of the gallium nitride layer (4) is 0.1 to 3 μm.
8. The dual-gate controlled dual-heterojunction GaN HEMT ultraviolet detector according to claim 1, characterized in that: The source (6), drain (7), front gate (8) and back gate (9) are made of one of Ti, Al, Ni and Au.
9. A preparation method, characterized in that: Used to prepare the dual-gate controlled dual heterojunction GaN HEMT ultraviolet detector according to any one of claims 1 to 8; The steps are as follows: A buffer layer (2), a bottom aluminum gallium nitride alloy layer (3), a gallium nitride layer (4), and a top aluminum gallium nitride alloy layer (5) are grown sequentially on a substrate (1). Fabricate the back gate (9); Source (6), drain (7) and front gate (8) are fabricated on the top aluminum gallium nitride alloy layer (5); The growth is performed using a metal-organic chemical vapor deposition method.
10. The preparation method according to claim 9, characterized in that: The source electrode (6) and drain electrode (7) are prepared by sputter magnetron sputtering and annealed at a temperature of 500 to 850°C for 30 seconds to 10 minutes.