An annular grating heterojunction solar blind detector and a preparation method thereof

Abstract

The application discloses a ring-shaped grating heterojunction solar-blind detector and a preparation method thereof, wherein the detector comprises a back electrode, a diamond layer, a Ga2O3 layer, a ring-shaped grating and an interdigital electrode; the diamond layer is arranged at the top end of the back electrode, the Ga2O3 layer is arranged at the top end of the diamond layer, the ring-shaped grating is arranged at the top end of the Ga2O3 layer, and the interdigital electrode is arranged at the central position of the top end of the ring-shaped grating; the application is more efficient in utilizing incident light, the light intensity threshold of detectable light is lower, the light absorption efficiency is improved, and the weak light detection capability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field, and more specifically, to an annular grating heterojunction solar-blind detector and a preparation method thereof. Background Art

[0002] Ultra-wide bandgap semiconductor solar-blind ultraviolet detection has important applications in military early warning, target identification, guidance, environmental monitoring and other fields, and has received widespread attention in recent years. As a typical representative of ultra-wide bandgap semiconductors, diamond has the characteristics of strong radiation resistance, high thermal conductivity, and high breakdown electric field. Its light absorption is in the extreme ultraviolet region, that is, the wavelength is <210nm, which is very suitable for deep ultraviolet detection in extreme environments. However, its shortcomings are: the light absorption coefficient in the solar-blind band is small and n-type doping is difficult. Therefore, the light response of a single diamond detector in the solar-blind band is weak, making it difficult to apply directly. Compared with diamond, gallium oxide (Ga2O 3） The semiconductor band gap is 5.0eV, and its light absorption coefficient in the solar-blind band is >10 5 cm -1 , making it an ideal material for solar-blind photoelectric detection. However, its drawbacks include low thermal conductivity and difficulty in p-type doping, making Ga2O3 detectors incapable of self-powering. Addressing the challenges of diamond-based solar-blind detectors, such as weak light absorption, lack of self-power capability, and weak light detection, is gaining increasing attention. Summary of the Invention

[0003] In order to overcome the problems of weak light absorption and difficulty in weak light detection in the above-mentioned prior art, the present invention provides a ring-shaped grating heterojunction solar-blind detector and a preparation method thereof, which can more efficiently utilize incident light, lower the light intensity threshold of detectable light, improve light absorption efficiency, and enhance weak light detection capability.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] The present invention discloses, on one hand, a ring-shaped grating heterojunction solar-blind detector, comprising:

[0006] Back electrode, diamond layer, Ga2O3 layer, annular grating, interdigitated electrodes;

[0007] The diamond layer is arranged on the top of the back electrode, the Ga2O3 layer is arranged on the top of the diamond layer; the annular grating is arranged on the top of the Ga2O3 layer; back electrode, diamond layer, Ga2O3 layer, annular grating, interdigitated electrode;

[0008] The diamond layer is arranged on the top of the back electrode, the Ga2O3 layer is arranged on the top of the diamond layer; the annular grating is arranged on the top of the Ga2O3 layer;

[0009] The interdigital electrode is arranged at the top end of the ring-shaped grating and contacts the top end of the Ga2O3 layer, and the interdigital part of the interdigital electrode is located at the center position of the top end of the ring-shaped grating.

[0010] Preferably, the back electrode has a thickness of 100-150 nm.

[0011] The diamond layer has a thickness of 150-300 μm.

[0012] The Ga2O3 layer has a thickness of 200-500 nm.

[0013] The interdigital electrode has a thickness of 100-150 nm, and the interdigital spacing of the interdigital electrode is 3-10 μm.

[0014] Preferably, the Ga2O3 layer comprises an intrinsic i-Ga2O3 layer and an n-Ga2O3 layer.

[0015] The n-Ga2O3 layer comprises x periods of growth layers, wherein one period of growth layers comprises an i-Ga2O3 layer and a Sn: Ga2O3 layer.

[0016] Further, the thickness of the i-Ga2O3 and Sn: Ga2O3 in the growth layer is less than 5 nm.

[0017] Another aspect of the present application discloses a preparation method of a ring-shaped grating heterojunction solar blind detector.

[0018] The B-doped p-type diamond layer is grown on the diamond single crystal substrate by using borane BH3 as a doping source through MPCVD;

[0019] The back electrode is evaporated on the diamond;

[0020] The Ga2O3 layer is grown on the diamond layer by MBE, and the Ga2O3 layer is doped by using a periodic delta-type modulation doping technology.

[0021] The ring-shaped grating is formed by etching the Ga2O3 layer;

[0022] The interdigital electrode is made on the ring-shaped grating.

[0023] Further, before the B-doped p-type diamond layer is grown, the substrate is mechanically polished, and then sequentially ultrasonic cleaned with acetone, ethanol and deionized water, and dried for standby use.

[0024] Hydrogen, methane and borane are introduced into the reaction chamber, and plasma is generated by microwave radiation, so that the methane and borane are decomposed and react with hydrogen to generate active groups; the active groups are deposited on the substrate to grow the diamond layer.

[0025] Furthermore, a Ga2O3 layer is grown on the diamond layer by MBE; and the Ga2O3 layer is doped using a periodic delta-type modulation doping technique, specifically comprising:

[0026] Using the δ-type modulation doping method and atomic-level regulation through MBE, an intrinsic i-Ga2O3 buffer layer is first grown on the diamond film, and then the i-Ga2O3 / Sn: Ga2O3 modulation doping superlattice is grown in sequence to construct the n-Ga2O3 layer.

[0027] Furthermore, etching the Ga2O3 layer to form a ring grating specifically includes:

[0028] Through photolithography, the photoresist is patterned as a mask for ICP, and then the Ga2O3 layer without mask coverage is etched by ICP to form grooves. Finally, the photoresist mask is removed by ICP and bombarded with oxygen plasma to obtain a ring grating.

[0029] Furthermore, the duty cycle and period of the annular grating satisfy the grating diffraction condition and the second-order Bragg condition;

[0030] The second-order Bragg conditions are as follows:

[0031]

[0032] The grating diffraction conditions are as follows:

[0033]

[0034] in is the angle of incidence, is the exit angle, is the grating period.

[0035] Furthermore, fabricating interdigitated electrodes on the annular grating specifically includes:

[0036] Photolithography is performed on the annular grating to make a photoresist mask, and then the top metal electrode is evaporated. The excess photoresist and metal are removed by soaking in a degumming solution, and annealing is performed to eliminate the interface stress between the metal electrode and the lower material of the metal electrode to form an ohmic contact, and finally form an interdigitated electrode.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. Through the second-order diffraction of the annular grating, the incident light and scattered light are converged, the incident light is utilized more efficiently, the light intensity threshold of the detectable light is lowered, and the problem of weak light absorption and difficulty in detecting weak light is solved.

[0039] 2. The interdigitated electrodes at the top are easy to integrate and can quickly collect photogenerated carriers. The small interdigital spacing improves the transient response speed of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a cross-sectional view of a ring-shaped grating heterojunction solar-blind detector provided in an embodiment.

[0041] Figure 2 This is a top view of a ring-shaped grating heterojunction solar-blind detector provided in an embodiment.

[0042] Figure 3 Schematic diagram of the ring grating principle provided by the embodiment.

[0043] Among them: 1. back electrode; 2. diamond layer; 3. Ga2O3 layer; 4. annular grating; 5. interdigitated electrode. DETAILED DESCRIPTION

[0044] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] In this embodiment, if Figure 1 、 Figure 2 As shown, a ring-shaped grating heterojunction solar-blind detector comprises:

[0047] Back electrode 1, diamond layer 2, Ga2O3 layer 3, annular grating 4, interdigitated electrode 5;

[0048] The diamond layer 2 is arranged on the top of the back electrode 1, the Ga2O3 layer 3 is arranged on the top of the diamond layer 2; the annular grating 4 is arranged on the top of the Ga2O3 layer 3; and the interdigitated electrode 5 is arranged at the top center position of the annular grating 4.

[0049] The interdigitated electrode 5 is disposed at the top of the annular grating 4 and contacts the top of the Ga 2 O 3 layer 3 . The interdigitated portion of the interdigitated electrode 5 is located at the top center of the annular grating 4 .

[0050] In this embodiment, the thickness of the back electrode 1 is 100-150 nm.

[0051] The thickness of the diamond layer 2 is 150-300 μm.

[0052] The thickness of the Ga2O3 layer 3 is 200-500nm.

[0053] The thickness of the interdigitated electrodes 5 is 100-150 nm, and the interdigital spacing between the interdigitated electrodes 5 is 3-10 μm.

[0054] In this embodiment, the Ga2O3 layer 3 includes an intrinsic i-Ga2O3 layer and an n-Ga2O3 layer.

[0055] The n-Ga2O3 layer comprises x periods of growth layers, one of which includes a layer of i-Ga2O3 and a layer of Sn:Ga2O3. These two layers constitute a cycle, and the growth is repeated for five cycles, with no strict requirement for the number of cycles. This reduces the Sn acceptor ionization energy within the Ga2O3 film and suppresses the formation of point defects and dislocation lines.

[0056] More specifically, the thickness of i-Ga2O3 and Sn:Ga2O3 in the growth layer is less than 5nm.

[0057] Example 2

[0058] In this embodiment, a method for preparing an annular grating heterojunction solar-blind detector, using the annular grating heterojunction solar-blind detector described in Example 1, includes:

[0059] MPCVD is used on a diamond single crystal substrate, using borane BH3 as a doping source to grow a B-doped p-type diamond layer 2;

[0060] Evaporating a back electrode 1 on the diamond;

[0061] A Ga2O3 layer 3 is grown on the diamond layer 2 by MBE; the Ga2O3 layer 3 is doped by a periodic delta-type modulation doping technique;

[0062] Etching is performed on the Ga2O3 layer 3 to form a ring grating 4;

[0063] Interdigitated electrodes 5 are formed on the annular grating 4 .

[0064] More specifically, before growing the B-doped p-type diamond layer 2, the substrate is mechanically polished, ultrasonically cleaned with acetone, ethanol, and deionized water in sequence, and blown dry for later use;

[0065] Hydrogen, methane and borane are introduced into the reaction chamber, and microwave radiation is used to generate plasma, causing the methane borane to decompose and react with hydrogen to generate active radicals; the active radicals are deposited on the substrate to grow a diamond layer 2.

[0066] More specifically, the Ga2O3 layer 3 is grown on the diamond layer 2 by MBE; and the Ga2O3 layer 3 is doped using a periodic delta-type modulation doping technique, specifically including:

[0067] Using a delta-type modulation doping method, controlled by MBE at the atomic level, an i-Ga2O3 buffer layer is first grown on a diamond film, followed by the sequential growth of an i-Ga2O3 / Sn:Ga2O3 modulation doping superlattice. This reduces the Sn acceptor ionization energy within the Ga2O3 film, while suppressing the formation of point defects and dislocation lines.

[0068] More specifically, etching the Ga2O3 layer 3 to form the annular grating 4 specifically includes:

[0069] Through photolithography, the photoresist is patterned as a mask for ICP, and then the Ga2O3 layer without mask coverage is etched by ICP to form grooves. Finally, the photoresist mask is removed by oxygen plasma bombardment through ICP to obtain the annular grating 4.

[0070] More specifically, the duty cycle and period of the annular grating 4 satisfy the grating diffraction condition and the second-order Bragg condition;

[0071] The second-order Bragg conditions are as follows:

[0072]

[0073] The grating diffraction conditions are as follows:

[0074]

[0075] in is the angle of incidence, is the exit angle, is the grating period.

[0076] Second-order diffracted light propagates parallel to the grating surface, reflecting optical feedback caused by the periodic ring grating 4. The second-order diffracted light couples with light traveling in the same or opposite direction, generating strong interference perpendicular to the grating lines. Because the refractive index of Ga2O3 and diamond is closer than that of air, resulting in a higher degree of admittance matching, most light preferentially propagates toward the interface between the diamond and Ga2O3 layers. Ring grating 4 serves to focus the incident light on the heterojunction region.

[0077] In this embodiment, if Figure 3 As shown, a groove and a protrusion constitute a grating period. According to the second-order grating diffraction and Bragg condition, the first-order diffracted light reflects the surface light loss, and the second-order diffracted light reflects the grating light feedback. The light propagating parallel to the grating interface will couple with its second-order diffracted light and reflect back and forth in the grating. Since the coupled light in all directions will propagate to the center of the grating, it has a focusing effect.

[0078] More specifically, manufacturing the interdigitated electrodes 5 on the annular grating 4 specifically includes:

[0079] Photolithography is performed on the annular grating 4 to make a photoresist mask, and then the top metal electrode is evaporated. The excess photoresist and metal are removed by soaking in a degumming solution, and annealing is performed to eliminate the interface stress between the metal electrode and the lower material of the metal electrode to form an ohmic contact, and finally form an interdigitated electrode 5.

[0080] The annular grating 4 is conducive to the collection and propagation of the light to be detected to the heterojunction region. The top interdigital electrode and the back electrode 1 construct a high field region between the diamond hole collector, the heterojunction light absorption region and the top interdigital Ga2O3 electron collector, so as to realize efficient separation and collection of the photoexcited electron-hole pairs, avoid the parasitic capacitance of the diamond bottom electrode, and inhibit the carrier consumption caused by the "recombination effect".

[0081] In order to overcome the bottleneck of diamond heterojunction growth, the interface polarity regulation technology is used to complete the matching of the Ga growth surface and the diamond interface, and to inhibit the interface defects caused by the O-polar surface. In view of the n-type doping problem of the ultra-wide bandgap β-Ga2O3, the periodic δ-type modulation doping technology is innovatively proposed to reduce the donor ionization energy and obtain high-concentration electrons to inhibit the generation of point defects. The annular grating 4 structure is designed to make the incident light converge and propagate to the heterojunction region, increase the utilization rate of incident light, and improve the sensitivity of the photodetector in harsh environments. The heterojunction detector constructed by diamond and Ga2O3 will have the advantages of self-power supply, low dark current, high signal-to-noise ratio, and high ultraviolet / visible rejection ratio.

[0082] Embodiment 3

[0083] In this embodiment, a heterojunction ultraviolet solar blind detector is constructed by combining diamond as a substrate and Ga2O3 film, which fully utilizes the respective characteristics of the two ultra-wide bandgap semiconductors to realize complementary advantages. The periodic δ-type modulation doping technology is innovatively used for n-type Ga2O3 doping to obtain high-concentration carriers. The integrable top interdigital structure is designed to assist the efficient separation of photo-generated carriers in the junction region, and together with the back electrode 1, it can well inhibit the "parasitic capacitance". The annular grating 4 structure is designed to make the incident light converge and propagate to the heterojunction region, increase the utilization rate of incident light, and improve the sensitivity of the photodetector in harsh environments, which can be used in the new generation of diamond-based ultraviolet solar blind detection chip technology. The specific technical scheme is described as follows.

[0084] In this embodiment, MPCVD means microwave plasma chemical vapor deposition, MBE means molecular beam epitaxy, and ICP etching means inductively coupled plasma etching.

[0085] Firstly, the characteristics of Ga and O polar growth surfaces of Ga2O3 material are simulated by software to study the influence of Ga and O polar surfaces of Ga2O3 on crystal phase, dangling bonds and interface energy band. The formation energy of various point defects in β-Ga2O3 is analyzed, especially the formation energy of oxygen vacancies in different components and its influence on carrier concentration and film conductivity, so as to guide the subsequent growth and preparation.

[0086] Subsequently, a boron-doped p-type diamond layer 2 was grown on a diamond single crystal substrate using MPCVD, using borane (BH3) as the doping source. The researchers systematically investigated the effects of different single-crystal diamond growth planes, interface control, and growth processes on boron doping, aiming to achieve high-quality p-diamond films with high boron acceptor concentrations, low defects, and low ionization energies. By optimizing interface control, they suppressed the formation of interface states, reduced deep-level traps, and effectively increased the hole concentration in the p-type diamond film.

[0087] A low-temperature metallic Ga layer, a low-temperature intrinsic Ga2O3 layer, and a high-density Ga2O3 layer were sequentially grown on a p-diamond substrate using MBE. The metallic Ga layer effectively relieves stress, promotes the growth of Ga polar faces, and reduces the density of point defects and dislocation lines within the Ga2O3 film. The low-temperature intrinsic Ga2O3 layer serves as a nucleation site for the subsequent two-dimensional growth of Ga2O3 thin films. The use of a Ga / Ga2O3 composite buffer layer addresses the lattice stress and thermal adaptation issues during epitaxial growth.

[0088] Using periodic δ-modulation doping technology, i-Ga2O3 / Sn:Ga2O3 modulation-doped superlattice is sequentially grown on the intrinsic i-Ga2O3 layer. This structure can effectively reduce the Sn acceptor ionization energy in the Ga2O3 film and inhibit the formation of point defects and dislocation lines.

[0089] Using the finite difference time domain (FDTD) method, researchers simulated the changes in the light field distribution generated by diffraction from a ring grating (4) within the device, optimizing the grating period and duty cycle for optimal focusing. Software was used to construct a p-diamond / n-Ga2O3 heterojunction and simulate the heterojunction device. Based on the simulation results, structural parameters were optimized. By adjusting the interdigital width, interdigital spacing, and electron-hole collector spacing, the device's IV characteristics, on-off ratio, and the spatial distribution of the heterojunction's built-in electric field were determined. This provided technical insights and specific parameters for heterojunction thin film growth, modulated doping, and micro-nano device fabrication.

[0090] Diamond / Ga2O3 heterojunction devices are fabricated using methods such as photolithography, ICP dry etching, electron beam evaporation, thermal evaporation, and rapid annealing. First, a back electrode 1 is evaporated on the diamond. Then, a ring-shaped grating 4 is fabricated on the Ga2O3 surface via photolithography and ICP etching. Finally, top ohmic contact interdigital electrodes are formed on the grating. Annealing eliminates interfacial stress between the electrodes and the underlying material, enhancing ohmic contact formation.

[0091] Finally, the production of high-performance self-powered diamond-based heterojunction solar-blind detector was completed.

[0092] Obviously, the above-mentioned embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Any modification, equivalent replacement and improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A ring-shaped grating heterojunction solar-blind detector, characterized in that: include: Back electrode, diamond layer, Ga2O3 layer, annular grating, interdigitated electrodes; The diamond layer is provided on the top of the back electrode, and the Ga2O3 layer is provided on the top of the diamond layer; the top of the Ga2O3 layer is etched to form the annular grating; The interdigitated electrode is provided at the top of the annular grating and contacts the top of the Ga2O3 layer, and the interdigitated portion of the interdigitated electrode is located at the top center of the annular grating; the duty cycle and period of the annular grating satisfy the grating diffraction condition and the second-order Bragg condition; The second-order Bragg conditions are as follows: The grating diffraction conditions are as follows: in is the angle of incidence, is the exit angle, is the grating period.

2. The annular grating heterojunction solar-blind detector according to claim 1, characterized in that: The thickness of the back electrode is 100-150 nm; The thickness of the diamond layer is 150-300 μm; The thickness of the Ga2O3 layer is 200-500nm; The thickness of the interdigitated electrodes is 100-150 nm, and the interdigital spacing of the interdigitated electrodes is 3-10 μm.

3. The annular grating heterojunction solar-blind detector according to claim 1, characterized in that: The Ga2O3 layer includes an intrinsic i-Ga2O3 layer and an n-Ga2O3 layer; The n-Ga2O3 layer includes x periods of growth layers, and one period of growth layer includes a layer of i-Ga2O3 and a layer of Sn:Ga2O3.

4. The annular grating heterojunction solar-blind detector according to claim 3, characterized in that: The thickness of i-Ga2O3 and Sn:Ga2O3 in the growth layer is less than 5nm.

5. A method for preparing a circular grating heterojunction solar-blind detector, using the circular grating heterojunction solar-blind detector according to any one of claims 1 to 4, characterized in that: include: MPCVD was used to grow a B-doped p-type diamond layer on a diamond single crystal substrate using borane BH3 as a doping source; After cleaning and drying the diamond, gold plating is performed to form a back electrode; A Ga2O3 layer is grown on a diamond layer by MBE; the Ga2O3 layer is doped using a periodic delta-type modulation doping technique; Etching is performed on the Ga2O3 layer to form a ring grating; Interdigitated electrodes are fabricated on the annular grating.

6. The method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: Before growing the B-doped p-type diamond layer, the substrate was mechanically polished, ultrasonically cleaned with acetone, ethanol, and deionized water in sequence, and dried for later use; Hydrogen, methane and borane are introduced into the reaction chamber, and microwave radiation is used to generate plasma, causing the methane borane to decompose and react with hydrogen to generate active groups; the active groups are deposited on the substrate to grow a diamond layer.

7. The method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: A Ga2O3 layer is grown on the diamond layer by MBE. The Ga2O3 layer is doped using a periodic delta-type modulation doping technique, specifically including: Using the δ-type modulation doping method and atomic-level regulation through MBE, an intrinsic i-Ga2O3 buffer layer is first grown on the diamond film, and then the i-Ga2O3 / Sn: Ga2O3 modulation doping superlattice is grown in sequence to construct the n-Ga2O3 layer.

8. The method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: Etching the Ga2O3 layer to form a ring grating specifically includes: Through photolithography, the photoresist is patterned as a mask for ICP, and then the Ga2O3 layer without mask coverage is etched by ICP to form grooves. Finally, the photoresist mask is removed by ICP and bombarded with oxygen plasma to obtain a ring grating.

9. The method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: The process of making interdigitated electrodes on annular gratings specifically includes: Photolithography is performed on the annular grating to make a photoresist mask, and then the top metal electrode is evaporated. The excess photoresist and metal are removed by soaking in a degumming solution, and annealing is performed to eliminate the interface stress between the metal electrode and the lower material of the metal electrode to form an ohmic contact, and finally form an interdigitated electrode.

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