Annular grating heterojunction solar blind detector and preparation method thereof

Abstract

The invention discloses an annular grating heterojunction solar blind detector and a preparation method thereof. The detector comprises a back electrode, a diamond layer, a Ga2O3 layer, an annular grating and an interdigital electrode. The diamond layer is arranged at the top end of the back electrode, and the Ga2O3 layer is arranged at the top end of the diamond layer; the annular grating is arranged at the top end of the Ga2O3 layer; the interdigital electrode is arranged at the central position of the top end of the annular grating; incident light is utilized more efficiently, the light intensity threshold value of detectable light is lower, the light absorption efficiency is improved, and the weak light detection capacity 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 and it is 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 , is an ideal solar-blind photoelectric detection material. Its shortcomings are: low thermal conductivity and difficulty in p-type doping, so Ga2O3 detectors cannot achieve self-powered operation. How to solve the problems faced by diamond-based solar-blind detectors, such as weak light absorption, no self-powered ability, and weak light detection, has received 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 interdigitated electrode is arranged at the top of the annular grating and contacts the top of the Ga2O3 layer. The interdigitated part of the interdigitated electrode is located at the center of the top of the annular grating.

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

[0011] The thickness of the diamond layer is 150-300 μm;

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

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

[0014] Preferably, the Ga2O3 layer includes an intrinsic i-Ga2O3 layer and an n-Ga2O3 layer;

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

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

[0017] Another aspect of the present invention discloses a method for preparing an annular grating heterojunction solar-blind detector, which uses the annular grating heterojunction solar-blind detector, comprising:

[0018] MPCVD is used to grow a B-doped p-type diamond layer on a diamond single crystal substrate using borane BH3 as a doping source;

[0019] Evaporating a back electrode on diamond;

[0020] A Ga2O3 layer is grown on the diamond layer by MBE; the Ga2O3 layer is doped by periodic delta-type modulation doping technology;

[0021] Etching is performed on the Ga2O3 layer to form a ring grating;

[0022] Interdigitated electrodes are fabricated on the annular grating.

[0023] Furthermore, before growing the B-doped p-type diamond layer, the substrate is mechanically polished, ultrasonically cleaned with acetone, ethanol, and deionized water in sequence, and blown dry for later use;

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

[0025] Further, a Ga2O3 layer is grown on the diamond layer by MBE; and the Ga2O3 layer is doped by periodic delta-type modulation doping technology, specifically including:

[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] Further, 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 oxygen plasma bombardment through ICP 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] 2 eff a=2λ

[0032] The grating diffraction conditions are as follows:

[0033] sinθ=sinφ+mλ / eff a(=0,1,2,3)

[0034] Where θ is the incident angle, φ is the exit angle, and a is the grating period.

[0035] Furthermore, manufacturing the 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 a forked finger electrode is formed.

[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 used 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 electrode at the top is 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 It is a top view of a ring-shaped grating heterojunction solar-blind detector provided in an embodiment.

[0042] Figure 3 It is a schematic diagram of the principle of the annular grating provided in 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 is in contact with 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 Ga2O3 layer 3 has a thickness of 200-500nm.

[0053] The thickness of the interdigitated electrode 5 is 100-150 nm, and the interdigital spacing of the interdigitated electrode 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 includes x periods of growth layers, wherein one period of growth layers includes a layer of i-Ga2O3 and a layer of Sn:Ga2O3. These two layers are taken as one period, and the growth is repeated for 5 periods, and there is no strict requirement for the number of periods. The ionization energy of Sn acceptors in the Ga2O3 film is reduced, and the formation of point defects and dislocation lines is suppressed at the same time.

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

[0057] Example 2

[0058] In this embodiment, a method for preparing a ring-shaped grating heterojunction solar-blind detector, using the ring-shaped grating heterojunction solar-blind detector described in Embodiment 1, comprises:

[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] Vapor depositing a back electrode 1 on diamond;

[0061] A Ga2O3 layer 3 is grown on the diamond layer 2 by MBE; and 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 plasma is generated by microwave radiation, so that methane borane decomposes and reacts with hydrogen to generate active groups; the active groups 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 by periodic delta-type modulation doping technology, which specifically includes:

[0067] Using the δ-type modulation doping method, MBE is used for atomic-level regulation to first grow an i-Ga2O3 buffer layer on the diamond film, and then sequentially grow i-Ga2O3 / Sn:Ga2O3 modulation doping superlattice. This reduces the Sn acceptor ionization energy in the Ga2O3 film and inhibits 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] 2 eff a=2λ

[0073] The grating diffraction conditions are as follows:

[0074] sinθ=sinφ+mλ / eff a(=0,1,2,3...)

[0075] Where θ is the incident angle, φ is the exit angle, and a is the grating period.

[0076] The second-order diffraction light propagates parallel to the grating surface, reflecting the light feedback caused by the periodic ring grating 4. The second-order diffraction light couples with the light with the same or opposite propagation direction, and produces strong interference in the direction perpendicular to the grating lines. Since the refractive index between Ga2O3 and diamond is closer than that of air, the admittance matching degree is higher, so most of the light preferentially propagates to the junction of diamond and Ga2O3 layers. The ring grating 4 plays the role of converging the incident light to the heterojunction area.

[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 the Bragg condition, the first-order diffraction light reflects the surface light loss, and the second-order diffraction light reflects the grating light feedback. The light propagating in the parallel grating interface will couple with its second-order diffraction 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, and the excess photoresist and metal are removed by soaking in a degumming solution. 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 a forked finger electrode 5 is formed.

[0080] The annular grating 4 facilitates the gathering and propagation of the light to be detected to the heterojunction region. The top interdigitated electrode and the back electrode 1 construct a spatial high field strength region between the diamond hole collector, the heterojunction light absorption region, and the top interdigitated Ga2O3 electron collector to achieve efficient separation and collection of electron-hole pairs excited by solar-blind photons; avoid the parasitic capacitance of the diamond bottom electrode, and suppress the carrier consumption caused by the "recombination effect".

[0081] In order to overcome the bottleneck of diamond heterojunction growth, the interface polarity control technology is used to match the Ga growth surface with the diamond interface, and the interface defects caused by the O polar surface are suppressed. In view of the difficulty of n-type doping of ultra-wide bandgap β-Ga2O3, an innovative periodic δ-type modulation doping technology is proposed to reduce the donor ionization energy to obtain high-concentration electrons to suppress the generation of point defects. In addition, a ring grating 4 structure is designed so that the incident light can be converged and propagated to the heterojunction area, increasing the utilization rate of the incident light and improving the sensitivity of the photodetector in harsh environments. The heterojunction detector constructed with diamond and Ga2O3 will have the advantages of self-powered, low dark current, high signal-to-noise ratio, and high UV / visible suppression ratio.

[0082] Example 3

[0083] In this embodiment, a heterojunction ultraviolet solar-blind detector is constructed by combining diamond with Ga2O3 thin film as the substrate, making full use of the respective characteristics of the two ultra-wide bandgap semiconductors to achieve complementary advantages. The innovative use of periodic δ-type modulation doping technology is used for n-type Ga2O3 doping to obtain high-concentration carriers. The design of an integrated top fork-finger structure auxiliary junction area can efficiently separate photogenerated carriers, and together with the back electrode 1, it can well suppress the "parasitic capacitance". The design of the annular grating 4 structure allows the incident light to converge and propagate to the heterojunction area, increasing the utilization rate of the incident light and improving the sensitivity of the photodetector in harsh environments. It can be used in the new generation of diamond-based ultraviolet solar-blind detection chip technology. The specific technical solution is described as follows.

[0084] The MPCVD described in this embodiment is microwave plasma chemical vapor deposition, MBE is molecular beam epitaxy, and ICP etching is inductively coupled plasma etching.

[0085] First, the software is used to simulate the Ga and O polar growth surface characteristics of Ga2O3 materials, and the influence of Ga and O polar surfaces of Ga2O3 on crystal phase, dangling bonds, and interface energy bands is studied. The formation energy of various point defects in β-phase Ga2O3 is analyzed, especially the formation energy of oxygen vacancies in different components and their influence on carrier concentration and film conductivity, so as to guide the subsequent growth and preparation.

[0086] Subsequently, MPCVD was used on a diamond single crystal substrate, using borane BH3 as a doping source to grow a B-doped p-type diamond layer 2, and the effects of different single crystal diamond growth planes, interface regulation, and growth processes on B atom doping were systematically studied to achieve high-quality p-diamond films with high B acceptor concentration, low defects, and low ionization energy. By optimizing interface regulation, the formation of interface states was suppressed, deep energy level capture traps were reduced, and the hole concentration of the p-type diamond film was effectively increased.

[0087] MBE was used to sequentially grow a low-temperature metal Ga layer, a low-temperature intrinsic Ga2O3, and a high-Ga2O3 layer on a p-diamond substrate. The metal Ga layer can effectively release stress, promote the growth of Ga polar surfaces, and reduce the density of point defects and dislocation lines inside the Ga2O3 film. The low-temperature intrinsic Ga2O3 layer can serve as a nucleation point for the subsequent two-dimensional growth of Ga2O3 films. The Ga / Ga2O3 composite buffer layer was used to solve the lattice stress and thermal adaptation problems in epitaxial growth.

[0088] Using periodic δ modulation doping technology, i-Ga2O3 / Sn:Ga2O3 modulation doping superlattice is grown sequentially 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] Finite Difference Time Domain (FDTD) is used to simulate the changes in the light field distribution generated by the diffraction of the annular grating 4 in the device, and the grating period and duty cycle are optimized to obtain the best convergence effect. The software is used to construct the p-diamond / n-Ga2O3 heterojunction, simulate the heterojunction device, optimize the structural parameters according to the simulation results, and obtain the device IV characteristics, switching ratio and spatial distribution of the built-in electric field of the heterojunction by adjusting different interdigital widths, finger spacings, and electron-hole collector spacings, providing technical ideas and specific parameters for heterojunction film growth, modulation doping, and device micro-nano preparation.

[0090] Diamond / Ga2O3 heterojunction devices are prepared by photolithography, ICP dry etching, electron beam evaporation, thermal evaporation, rapid annealing and other methods. First, the back electrode 1 is evaporated on the diamond, and then the annular grating 4 is made on the Ga2O3 on the front side by photolithography and ICP etching. Finally, the top ohmic contact interdigital electrode is prepared on the grating. Annealing can eliminate the interface stress between the electrode and the material below, and better form the ohmic contact.

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

[0092] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

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 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; The interdigitated electrode is arranged at the top of the annular grating and contacts the top of the Ga2O3 layer. The interdigitated part of the interdigitated electrode is located at the center of the top of the annular grating.

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

3. A ring-shaped 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, wherein one period of growth layers includes a layer of i-Ga2O3 and a layer of Sn:Ga2O3.

4. A ring-shaped 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 claims 1 to 4, characterized in that: include: MPCVD is 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 is plated to form a back electrode; A Ga2O3 layer is grown on the diamond layer by MBE; the Ga2O3 layer is doped by periodic delta-type modulation doping technology; Etching is performed on the Ga2O3 layer to form a ring grating; Interdigitated electrodes are fabricated on the annular grating.

6. A 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 is mechanically polished, ultrasonically cleaned with acetone, ethanol, and deionized water in sequence, and blown dry for later use; Hydrogen, methane and borane are introduced into the reaction chamber, and plasma is generated by microwave radiation, so that methane borane decomposes and reacts with hydrogen to generate active groups; the active groups are deposited on the substrate to grow a diamond layer.

7. A method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: The Ga2O3 layer is grown on the diamond layer by MBE; the Ga2O3 layer is doped by periodic delta-type modulation doping technology, 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. A method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: Etching on 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 oxygen plasma bombardment through ICP to obtain a ring grating.

9. A method for preparing a ring-shaped grating heterojunction solar-blind detector according to claim 5, characterized in that: 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: 21neffa=221 The grating diffraction conditions are as follows: sinθ=sinφ+mλ / neffa(m=0,1,2,3...) Where θ is the incident angle, φ is the exit angle, and a is the grating period.

10. A 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 the annular grating 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 a forked finger electrode is formed.

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