A dual-ultraviolet band photodetector based on AlGaN / GaN HEMT and its fabrication method

Abstract

This invention discloses a dual-ultraviolet photodetector based on AlGaN / GaN HEMT and its fabrication method, belonging to the field of ultraviolet photodetector technology. The detector comprises, from bottom to top, a stacked AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer. A two-dimensional electron gas conductive channel is formed at the interface between the AlGaN barrier layer and the GaN channel layer. The front side of the detector has a source, a drain, and a Schottky ring gate. The source and drain form ohmic contacts with the two-dimensional electron gas conductive channel, and the Schottky ring gate is used to modulate the two-dimensional electron gas conductive channel. Ultraviolet light can be incident simultaneously from both the front and back sides of the detector, achieving dual-sided ultraviolet detection. Ultraviolet photoresponse is observed on both the front and back sides at different ultraviolet wavelengths, achieving dual-sided ultraviolet detection. It can also be used as a photoelectric logic unit to implement AND, OR, XOR, and other logic operations, suitable for ultraviolet communication and on-chip optoelectronic information processing integrated applications.

Description

Technical Field

[0001] This invention belongs to the field of ultraviolet photodetector technology, specifically relating to a dual ultraviolet band photodetector based on AlGaN / GaN HEMT and its fabrication method. Background Technology

[0002] High-performance ultraviolet photodetectors (UVPDs) are widely used in numerous fields, including flame detection, space exploration, environmental monitoring, medical diagnostics, missile contrail detection, and optical communication. While traditional silicon-based detectors are technologically mature, their performance degrades significantly under high temperatures and strong radiation. In contrast, group III nitride semiconductors, with their wide bandgap, excellent thermal stability, and strong radiation resistance, have become ideal choices for next-generation ultraviolet detection. Two-dimensional electron gases (2DEGs) formed based on AlGaN / GaN heterojunctions not only possess excellent electrical properties but also exhibit significant photoelectric responses to ultraviolet light, thus becoming an important research direction for ultraviolet detectors.

[0003] Meanwhile, with the rapid development of information technology, integrated circuits are facing increasingly stringent requirements for miniaturization, multifunctionality, and low power consumption. Traditional CMOS-based logic circuits typically require multiple transistors to perform basic logic operations, which not only limits integration density but also reduces energy efficiency. In recent years, reconfigurable logic devices have attracted much attention because they can implement multiple logic functions in a single device. For example, two-dimensional material heterojunctions, ferroelectric control devices, and vertical optotransistors have been used to implement logic gates such as AND, OR, NAND, NOR, and XNOR, thereby significantly reducing the number of devices required.

[0004] However, most existing reconfigurable logic schemes rely on complex external electrical control, such as multi-gate bias, electric field polarization control, or additional driving circuits. This increases system complexity and power consumption to some extent, weakening the advantages of single-device logic computation. Secondly, although some optoelectronic logic devices can achieve logic function switching, they typically only support a limited number of logic operations, or require changing the output decision threshold to achieve different logic modes, thus reducing the stability and practicality of logic operations. Furthermore, existing optical control logic is mostly based on unilateral optical excitation, with limited optical control dimensions, making it difficult to achieve high-degree-of-freedom input modulation and continuous programmable logic mapping. For GaN-based HEMT optoelectronic devices, although two-dimensional electron gas (2DEG) has highly sensitive modulation capabilities to illumination, the presence of the silicon substrate in the traditional structure restricts the back-side light incident path, limiting optical-electric coupling to unilateral control and making it difficult to fully utilize the synergistic effect of multi-region photogenerated carriers on channel conductivity. Therefore, how to introduce new optical control degrees of freedom while maintaining device structure simplicity, and achieve stable, low-power, and multifunctional optical reconfigurable logic, remains a key issue in current research. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT and its fabrication method, thereby solving the problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: A dual-ultraviolet photodetector based on AlGaN / GaN HEMT comprises, from bottom to top, the following layers stacked sequentially: an AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer. A two-dimensional electron gas conductive channel is formed at the interface between the AlGaN barrier layer and the GaN channel layer. The front side of the detector has a source, a drain, and a Schottky ring gate. The source and drain form ohmic contacts with the two-dimensional electron gas conductive channel, and the Schottky ring gate is used to modulate the two-dimensional electron gas conductive channel. Ultraviolet light can be incident simultaneously from both the front and back sides of the detector, achieving dual-sided ultraviolet detection.

[0007] Furthermore, the AlGaN back barrier layer has a thickness of 300-350 nm and an Al molar fraction of 25%; the GaN buffer layer has a thickness of 2-3 μm. Furthermore, the GaN channel layer is an unintentionally doped GaN channel layer with a thickness of 150 nm; the AlGaN barrier layer has a thickness of 18-25 nm and an Al molar fraction of 20-23%; and the GaN cap layer has a thickness of 2 nm.

[0008] Furthermore, the source electrode is made of Ti and Au, with thicknesses of 20 nm and 100 nm, respectively; the drain electrode is made of Ti and Au, with thicknesses of 20 nm and 100 nm, respectively; and the Schottky ring gate electrode is made of Ni and Au, with thicknesses of 20 nm and 100 nm, respectively.

[0009] The above-mentioned method for fabricating a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT includes the following steps: S1, an AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer are sequentially grown on a silicon substrate using a metal-organic chemical vapor deposition method. S2, using ion beam etching process, etches from the GaN cap layer down until the GaN channel layer is exposed, forming a device isolation structure; S3, deposit a SiO2 insulating layer on the exposed upper surface of the GaN channel layer and the upper surface of the GaN cap layer; then open source and drain contact windows on the upper surface of the GaN cap layer; S4, a Ti / Au metal layer is deposited within the contact window; then annealing is performed to form source and drain ohmic contacts; S5, deposit a Ni / Au metal layer on the upper surface of the GaN cap layer and between the source and drain to form a ring Schottky gate structure; S6, deposit a SiO2 passivation layer on the entire upper surface; pattern the surface using an etching process, and then deposit a Ti / Au metal interconnect structure on the SiO2 passivation layer; S7 uses a back-side etching process to remove the silicon substrate and thins the AlGaN back barrier layer and GaN buffer layer to obtain a back-side ultraviolet incident structure.

[0010] Furthermore, in S3, the SiO2 insulating layer is deposited using atomic layer deposition with a thickness of 20 nm; the source and drain contact windows are opened using reactive ion etching.

[0011] Furthermore, in S4, the annealing temperature is 450~500℃, the annealing atmosphere is nitrogen, and the annealing time is 60~120s.

[0012] Furthermore, in S6, the SiO2 passivation layer is deposited using plasma-enhanced chemical vapor deposition (PECVD) with a thickness of 200 nm; it is then patterned using RIE (Rich Interaction Engineering) and finally formed using physical vapor deposition (PECVD) to create a Ti / Au metal interconnect structure.

[0013] Furthermore, in S7, the silicon substrate is first removed using the DRIE process; then, the AlGaN back barrier layer and GaN buffer layer are thinned using an inductively coupled plasma etching process.

[0014] The above-mentioned application of the dual ultraviolet band photodetector based on AlGaN / GaNHEMT in ultraviolet communication and on-chip optoelectronic information processing integration.

[0015] The beneficial effects of this invention are: This invention rationally designs an AlGaN / GaN heterojunction structure, employing front-side mesa etching, electrode structure design and fabrication, back-side substrate hollowing, and back-side AlGaN back barrier layer thinning. The device exhibits typical photoresponse characteristics under both front-side 254nm and back-side 365nm illumination. When dual-wavelength and dual-side illumination are applied simultaneously, its photoresponse to 254nm light intensity exhibits non-monotonic characteristics. Therefore, by using the 254nm front-side light intensity and the 365nm back-side light intensity as two inputs and the drain current (IDS) as the output, this device implements seven reconfigurable logic operations, including XOR, AND, OR, NOT, NOR, NAND, and suppression, within a single HEMT structure, fully demonstrating its application potential in highly integrated, low-power intelligent optoelectronic systems. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating the fabrication process of the dual ultraviolet band photodetector of the AlGaN / GaN HEMT of the present invention. Figure 2 This is an optical microscope image of the photodetector prepared in Example 1 of the present invention; Figure 3 This is an optical microscope image of the photodetector prepared in Example 2 of the present invention; Figure 4 The image shows the photoresponse test results of the detector prepared in Example 1 of the present invention under frontal 254 nm illumination. Figure 5 The image shows the photoresponse test results of the detector prepared in Example 1 of the present invention under 365 nm back-side illumination. Figure 6 This is a graph showing the photoresponse test results of the detector prepared in Example 2 of the present invention under frontal 254 nm illumination; Figure 7 This is a graph showing the photoresponse test results of the detector prepared in Example 2 of the present invention under 365 nm back-side illumination; Figure 8 This is a graph showing the test results of the dual-wavelength, dual-sided illumination light response of the detector prepared in Embodiment 2 of the present invention; Figure 9 This is a schematic diagram demonstrating the reconfigurable logic gates of the detector prepared in Embodiment 2 of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1As shown, a dual-ultraviolet photodetector based on AlGaN / GaNHEMT comprises, from bottom to top, the following layers stacked sequentially: an AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer. A two-dimensional electron gas conductive channel is formed at the interface between the AlGaN barrier layer and the GaN channel layer. The front side of the detector (i.e., the upper surface of the GaN cap layer) is provided with a source, a drain, and a Schottky ring gate. The source and drain form ohmic contacts with the two-dimensional electron gas conductive channel, and the Schottky ring gate is used to modulate the two-dimensional electron gas. Ultraviolet light can be incident simultaneously from both the front and back sides of the detector, achieving dual-sided ultraviolet detection.

[0020] The AlGaN back barrier layer has a thickness of 300~350nm and an Al molar fraction of 25%. The GaN buffer layer is a high-resistivity GaN buffer layer with a thickness of 2~3μm; The GaN channel layer is an unintentionally doped GaN channel layer with a thickness of 150 nm; The AlGaN barrier layer has a thickness of 18-25 nm and an Al molar fraction of 20-23%. Furthermore, the thickness of the GaN cap layer is 2 nm.

[0021] The source electrode is made of Ti and Au, with thicknesses of 20 nm and 100 nm, respectively; the drain electrode is made of Ti and Au, with thicknesses of 20 nm and 100 nm, respectively; and the Schottky ring gate electrode is made of Ni and Au, with thicknesses of 20 nm and 100 nm, respectively.

[0022] like Figure 1 As shown, the fabrication method of the above-mentioned AlGaN / GaNHEMT-based dual-ultraviolet band photodetector includes the following steps: S1, an AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer are sequentially grown on a silicon substrate using a metal-organic chemical vapor deposition method. S2, the device isolation structure is formed by IBE (ion beam etching) process. The etching starts from the GaN cap layer and goes down until it reaches the depth of the GaN channel layer to achieve effective electrical isolation outside the two-dimensional electron gas region. S3, deposit a SiO2 insulating layer on the exposed upper surface of the GaN channel layer and the upper surface of the GaN cap layer (the SiO2 insulating layer covers the entire upper surface); then use an etching process to open source and drain contact windows on the upper surface of the GaN cap layer (before this, the SiO2 insulating layer is partially removed). S4, depositing Ti and Au metal layers within the contact window; then annealing in a nitrogen atmosphere to form source and drain ohmic contacts with low contact resistance; S5, Ni and Au metal layers are deposited on the upper surface of the GaN cap layer and between the source and drain to form a ring Schottky gate structure, so as to achieve effective control of the two-dimensional electron gas channel; S6, deposit a SiO2 passivation layer on the entire upper surface; after patterning by etching, deposit a Ti and Au metal interconnect structure on the upper surface of the SiO2 passivation layer; S7. Finally, the silicon substrate is removed by back-side etching, and the AlGaN back barrier layer and GaN buffer layer are thinned to obtain the back-side ultraviolet incident structure.

[0023] in: In S3, an ALD (atomic layer deposition) is used to deposit a SiO2 insulating layer with a thickness of 20 nm; the source and drain contact windows are opened using the RIE process.

[0024] In S4, within the contact window, a 20 nm thick Ti metal layer and a 100 nm thick Au metal layer are sequentially deposited by electron beam evaporation to form a source / drain electrode metal stack structure. The annealing parameters are: rapid thermal annealing, annealing temperature of 450~500℃, annealing atmosphere of nitrogen, and annealing time of 60~120s.

[0025] In S5, a double-layer metal stack structure is formed by sequentially depositing Ni with a thickness of 20 nm and Au with a thickness of 100 nm using electron beam evaporation.

[0026] In S6, a 200nm thick SiO2 passivation layer is applied using plasma-enhanced chemical vapor deposition (PECVD). The layer is patterned using RIE (Rigid Interchange) technology. A 50nm Ti layer is deposited sequentially as an adhesion layer and a 100nm Au layer as a conductive layer using physical vapor deposition (PVD) to form a metal interconnect structure, which is used to construct the metal connection of the lead regions of the source, drain, and gate.

[0027] In S7, the silicon substrate is completely removed using the DRIE process; then, the AlGaN back barrier layer is thinned using an inductively coupled plasma (ICP) etching process, with an etching time of 5 minutes.

[0028] The technical solution of the present invention will be described below through the following embodiments; Example 1 This embodiment provides a method for fabricating a silicon-based AlGaN / GaNHEMT dual-ultraviolet band photodetector, such as... Figure 1 As shown, it includes the following steps: First, an AlGaN back barrier layer, a GaN buffer layer, an unintentionally doped GaN channel layer, an AlGaN barrier layer, and a GaN cap layer were sequentially grown on a cleaned silicon substrate using MOCVD. The AlGaN back barrier layer had a thickness of 850 nm and an Al molar fraction of 25%; the GaN buffer layer had a thickness of 2 μm; the unintentionally doped GaN channel layer had a thickness of 150 nm; the AlGaN barrier layer had a thickness of 20 nm and an Al molar fraction of 20%; and the GaN cap layer had a thickness of 2 nm. The resulting sample was then cleaned and dried with nitrogen.

[0029] Next, the device was subjected to mesa isolation etching using an IBE process (argon gas value 7 sccm, rotation speed 10 RPM, energy 500 eV, beam current 90±2 mA, neutralization 120±15 mA, etching rate 35 nm-40 nm / min). The etching started from the GaN cap layer and proceeded downwards until it penetrated the GaN channel layer, reaching a depth of 60 nm, to achieve effective electrical isolation outside the two-dimensional electron gas region. A 20 nm thick SiO2 insulating layer was deposited on the exposed GaN channel layer and the GaN cap layer using the ALD method (at 250 °C). Subsequently, the source and drain contact windows were created using a RIE process. This insulating layer covers and protects the mesa sidewalls to reduce leakage current and improve device reliability.

[0030] Then, within the contact window, Ti / Au metal layers are deposited by electron beam evaporation (evaporation rate 0.5 nm / s, vacuum environment, pressure 5E-4 Pa, temperature 300℃), with thicknesses of 20 nm and 100 nm, respectively; followed by rapid thermal annealing at 500℃ for 2 min in a nitrogen atmosphere to form ohmic contacts between the source and drain with low contact resistance. Ni / Au metal layers are then deposited by electron beam evaporation on the surface of the GaN cap layer and between the source and drain electrodes (evaporation rate 0.5 nm / s, vacuum environment, pressure 5E-4 Pa, temperature 300℃), with thicknesses of 20 nm and 100 nm, respectively, to form a ring-shaped Schottky gate structure.

[0031] A 200 nm thick SiO2 passivation layer was deposited on the entire upper surface using PECVD (deposition rate 80 nm / min, deposition at 350 °C for 150 s). After patterning using RIE (etching rate 200 nm / min, etching for 60 s), a Ti / Au metal interconnect structure was formed using PVD. Subsequently, deep silicon etching was performed to gradually remove the silicon substrate (etching environment: C4F8 flow rate 200 sccm, SF6 flow rate 500 sccm, with SF6 as the etching gas and C4F8 as the passivation gas, alternating between the two). The device structure after removing the silicon substrate is shown below. Figure 2 As shown.

[0032] Example 2 This embodiment provides a dual-ultraviolet photodetector with back-side thinning of AlGaN / GaNHEMT and its fabrication method. The preceding process of Embodiment 2 is the same as that of Embodiment 1, including the design of the metal contact electrode. However, after the process of Embodiment 1 is completed, the AlGaN back barrier layer is thinned by ICP etching (Cl2 flow rate of 10 sccm, BCl3 flow rate of 25 sccm, ignition power of 100W, etching power of 300W, and etching rate of 100 nm / min). By controlling the etching time to 5 min, the thickness of the AlGaN back barrier layer after thinning is 350 nm, thereby forming a back-side ultraviolet incident structure.

[0033] The etched device structure behind it is as follows Figure 3 As shown, with Figure 2 The comparison shows that a semi-transparent area appears around the device, indicating that the thinning of the back side reduces the material thickness and improves the light transmission capability, providing a structural basis for realizing double-sided light incidence.

[0034] Experimental Test Experimental tests were conducted on the detectors prepared in Examples 1 and 2. The test procedure included: placing a 254 nm ultraviolet LED, an optical lens, and the device prepared in Example 1 at the same height and aligned along the same vertical axis; focusing the light beam emitted by the LED onto the front of the device through the optical lens. The device was connected to a semiconductor parameter analyzer (Agilent B1500A), with the source grounded, the drain bias fixed at 6 V, and the gate bias scanned from −8 V to 4 V in 20 mV steps. The incident light power density was changed by adjusting the LED driving voltage under dark conditions and at 0.1, 0.2, 0.5, 1, 1.5, 2, and 2.5 mW / cm². 2 The photoresponse was tested under varying light intensity. The light source was then replaced with a 365 nm ultraviolet LED, and the device orientation was adjusted so that the beam was focused onto the back of the device through a lens. The test process was repeated while keeping other experimental conditions and test parameters constant. Finally, the test device was replaced with the device prepared in Example 2, and all tests were repeated under the same experimental conditions for comparative analysis.

[0035] Test results are as follows Figures 4-7As shown, the drain current remains low under dark conditions, indicating good turn-off characteristics and low dark current. When 254 nm ultraviolet light is irradiated onto the front side of the device, the drain current increases with increasing incident light power density, and the transfer characteristic curve shifts towards the negative gate voltage direction, indicating that ultraviolet light effectively modulates the two-dimensional electron gas concentration and enhances conductivity. Under 365 nm back-side illumination, the device also exhibits photoresponse behavior. Further comparison of devices with different back-side etching depths reveals that the photoresponse intensity of the device prepared in Example 2 is significantly higher than that in Example 1. Moderate back-side etching improves light modulation efficiency while maintaining the integrity of the back barrier structure, thus resulting in superior photoelectric response performance. In summary, the results show that the double-sided light incident structure achieved through substrate removal and back-side thinning not only broadens the ultraviolet detection methods of the device but also provides a physical basis for the subsequent implementation of reconfigurable logic functions based on dual-wavelength light modulation.

[0036] Furthermore, the device prepared in Example 2 was subjected to dual-wavelength, bi-sided illumination testing. A 254 nm ultraviolet LED was used as the front incident light source, and a 365 nm ultraviolet LED was used as the back incident light source. The two beams were focused onto the front and back sides of the device through optical lenses, respectively, to achieve independent optical excitation on both sides. The device was connected to a semiconductor parameter analyzer (Agilent B1500A), with the source grounded, the drain bias fixed at 6 V, and the gate bias maintained at −2.3 V. The incident light intensity was controlled by adjusting the LED driving voltage, with the driving voltage of the 254 nm LED gradually increased from 5 V to 7.4 V, and the driving voltage of the 365 nm LED gradually increased from 3 V to 5.4 V, with a voltage step size of 0.2 V for both. The changes in the device drain current were recorded under different dual-wavelength light intensity combinations.

[0037] Test results are as follows Figure 8 As shown, under simultaneous dual-wavelength illumination, the device drain current exhibits a distinct non-monotonic trend with varying 254nm light intensity. When the 365nm back illumination remains constant, the drain current initially increases with gradually increasing 254nm front illumination intensity, but then decreases after reaching a certain intensity. This tunable nonlinear optical response caused by the synergistic effect of the dual wavelengths allows the device output current to exhibit distinguishable stable current states under different light intensity combinations.

[0038] Therefore, by defining 254 nm front illumination and 365 nm back illumination as two independent optical input signals, and by setting a drain current threshold as the output criterion, a logical mapping relationship between optical input and electrical output can be established. The results are as follows: Figure 9 As shown: Among them, Figure 9(a) in the figure is a two-dimensional distribution diagram of drain current IDS as a function of light intensity at 254 nm and 365 nm. Different color areas correspond to different current output states and indicate the distribution of achievable logic function areas. Figure 9 Tables (b) to (h) show the specific logical operation results achieved under different light intensity combinations. Among them: Figure 9 (b) in the diagram corresponds to XOR (exclusive OR) logic. When the two optical inputs are different, the output is logic "1", and when the inputs are the same, the output is logic "0", which reflects the typical characteristics of XOR. Figure 9 (c) in the code represents AND logic, which outputs logic "1" only when both 254 nm and 365 nm light are in a high input state at the same time, and logic "0" in other cases. Figure 9 (d) in the diagram represents OR logic, which generates a logic "1" output as long as either optical input is high, and outputs a logic "0" only when both inputs are low. Figure 9 (e) represents NOT logic, where the output state is inversely correlated with the input optical signal, thus achieving single-input inversion. Figure 9 (f) in the code is a NOR (or NOT) logic, which outputs logic "1" only when both inputs are low light intensity, otherwise it outputs logic "0". Figure 9 (g) in the code represents NAND logic, which outputs logic "1" for all other input combinations except when both inputs are high simultaneously. Figure 9 The (h) in the code represents the Inhibit logic, which suppresses the output to logic "0" under specific optical input conditions, demonstrating the modulation and suppression effects between inputs. It can be seen that when the drain current is defined as logic "0" between 3.9 mA and 5.7 mA, and logic "1" elsewhere, seven different logic operations, including XOR, AND, OR, NOT, NOR, NAND, and suppression, can be implemented, realizing the application of its reconfigurable logic gates.

[0039] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A dual-ultraviolet band photodetector based on AlGaN / GaN HEMT, characterized in that, From bottom to top, the detector comprises, in sequence: an AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer. A two-dimensional electron gas conductive channel is formed at the interface between the AlGaN barrier layer and the GaN channel layer. The front side of the detector is provided with a source, a drain, and a Schottky ring gate. The source and drain form ohmic contacts with the two-dimensional electron gas conductive channel, and the Schottky ring gate is used to modulate the two-dimensional electron gas conductive channel. Ultraviolet light can be incident from both the front and back sides of the detector simultaneously, achieving double-sided ultraviolet detection.

2. The dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 1, characterized in that, The AlGaN back barrier layer has a thickness of 300-350 nm and an Al molar fraction of 25%; the GaN buffer layer has a thickness of 2-3 μm.

3. The dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 1, characterized in that, The GaN channel layer is an unintentionally doped GaN channel layer with a thickness of 150 nm; the AlGaN barrier layer has a thickness of 18-25 nm and an Al molar fraction of 20-23%; the GaN cap layer has a thickness of 2 nm.

4. A dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 1, characterized in that, The source electrode is made of Ti and Au, with thicknesses of 20 nm and 100 nm, respectively; the drain electrode is made of Ti and Au, with thicknesses of 20 nm and 100 nm, respectively; and the Schottky ring gate electrode is made of Ni and Au, with thicknesses of 20 nm and 100 nm, respectively.

5. A method for fabricating a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT as described in any one of claims 1-4, characterized in that, Includes the following steps: S1, an AlGaN back barrier layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer are sequentially grown on a silicon substrate using a metal-organic chemical vapor deposition method. S2, using ion beam etching process, etches from the GaN cap layer down until the GaN channel layer is exposed, forming a device isolation structure; S3, deposit a SiO2 insulating layer on the exposed upper surface of the GaN channel layer and the upper surface of the GaN cap layer; then open source and drain contact windows on the upper surface of the GaN cap layer; S4, a Ti / Au metal layer is deposited within the contact window; Then, annealing is performed to form ohmic contacts between the source and drain electrodes; S5, deposit a Ni / Au metal layer on the upper surface of the GaN cap layer and between the source and drain to form a ring Schottky gate structure; S6, deposit a SiO2 passivation layer on the entire upper surface; pattern the surface using an etching process, and then deposit a Ti / Au metal interconnect structure on the SiO2 passivation layer; S7 uses a back-side etching process to remove the silicon substrate and thins the AlGaN back barrier layer and GaN buffer layer to obtain a back-side ultraviolet incident structure.

6. The method for fabricating a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 5, characterized in that, In S3, the SiO2 insulating layer is deposited using atomic layer deposition with a thickness of 20 nm; the source and drain contact windows are opened using reactive ion etching.

7. The method for fabricating a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 5, characterized in that, In S4, the annealing temperature is 450~500℃, the annealing atmosphere is nitrogen, and the annealing time is 60~120s.

8. The method for fabricating a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 5, characterized in that, In S6, the SiO2 passivation layer is deposited using plasma-enhanced chemical vapor deposition (PECVD) with a thickness of 200 nm; it is then patterned using RIE (Rich Interaction Engineering) and finally formed into a Ti / Au metal interconnect structure using physical vapor deposition (PECVD).

9. The method for fabricating a dual-ultraviolet band photodetector based on AlGaN / GaN HEMT according to claim 5, characterized in that, In S7, the silicon substrate is first removed using the DRIE process; then, the AlGaN back barrier layer and GaN buffer layer are thinned using an inductively coupled plasma etching process.

10. The application of the dual ultraviolet band photodetector based on AlGaN / GaN HEMT as described in any one of claims 1-4 in the integration of ultraviolet communication and on-chip optoelectronic information processing.

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