A preparation method of a mixed-dimensional heterojunction photodiode based on a gallium nitride single crystal substrate
By fabricating a mixed-dimensional heterojunction photodiode on a gallium nitride single-crystal substrate, the problems of low responsivity and narrow spectral detection of existing vdWHs photodetectors have been solved, achieving high rectification ratio and wide spectral detection, thus improving the response speed and sensitivity of the device.
Patent Information
- Application Number
- CN202211716039.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-29
- Publication Date
- 2025-12-12
- Estimated Expiration
- 2042-12-29
AI Technical Summary
Existing vdWHs photodetectors suffer from low responsivity and narrow spectral range due to a lack of gain, numerous surface effects and defects, making it difficult to achieve both fast response and high sensitivity under extreme conditions and in multi-band broadband spectral detection.
A mixed-dimensional heterojunction photodiode fabrication method based on gallium nitride single-crystal substrate is adopted. A lightly doped n-type gallium nitride epitaxial layer is grown on the single-crystal substrate, a p-type two-dimensional material layer is deposited to form a vertical electrode structure, and a built-in electric field is formed by chemical vapor deposition doping to optimize the energy band arrangement to promote the separation of photogenerated carriers.
It achieves high rectification ratio and high optical switching ratio, enabling wide-spectrum detection in the ultraviolet to visible light range, reducing reverse leakage current and dark current, and improving the device's response speed and sensitivity.
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Figure CN115863488B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of semiconductors, and particularly relates to a preparation method of a mixed-dimensional heterojunction photodiode based on a gallium nitride monocrystal substrate. BACKGROUND
[0002] The third-generation semiconductor material represented by gallium nitride has superior properties such as a wide band gap, a high breakdown field, a high thermal conductivity, a high electron saturation velocity, and a strong anti-radiation capability. With its superior performance and huge market prospect, the third-generation semiconductor material has become the focus of competition in the global semiconductor market. Two-dimensional (2D) materials in atomic thin layers provide an excellent platform for creating new atomic-scale van der Waals heterostructures (vdWHs) due to their excellent mechanical, thermal, optical and electrical properties, and particularly the unique van der Waals force stacking without the obstacles of dangling bonds and lattice mismatch. Meanwhile, vdWHs have material and structural diversity, and can be stacked with zero-dimensional (quantum dots), one-dimensional (nanowires) and three-dimensional (bulk materials) in space to form mixed-dimensional heterostructures. The 2D / WBG mixed-dimensional vdWHs integrate the advantages of three-dimensional wide-bandgap functional materials (Eg>3eV) such as high frequency and high electron mobility, and the excellent properties of two-dimensional (2D) materials such as dangling-free surfaces and adjustable band gaps, and show great potential in the next generation of functional electronic and optoelectronic devices.
[0003] Among the reported vdWHs devices, self-powered photodiodes are characterized by energy consumption-free based on photovoltaic effect, and have attracted widespread attention due to their good fit with the urgent needs of the next generation of optoelectronic nanodevices. Importantly, compared with phototransistors or photoconductors, self-powered vdWH photodiodes have photovoltaic capability and fast response time.
[0004] Current vdWHs photodetectors have problems such as low response rate and detection in a narrow spectral range due to the lack of gain, many surface effects and defects, and a single band gap, which limits the application in extreme conditions and multi-band wide spectral detection, and it is difficult to balance fast response and high sensitivity, wide spectral detection and the like at the same time. SUMMARY
[0005] The embodiment of the application provides a preparation method of a mixed-dimensional heterojunction photodiode based on a gallium nitride monocrystal substrate, which comprises the following steps:
[0006] An epitaxial growth of a lightly doped n-type gallium nitride epitaxial layer is performed on a monocrystal substrate, and the epitaxial layer is cleaned and dried after being polished on both sides;
[0007] A p-type two-dimensional material layer Mo is deposited on the surface of the device by using a three-temperature zone tube furnace x Re 1-xS2, spin-coating photoresist, performing mask exposure pattern, developing and removing the photoresist to expose the two-dimensional material of the patterned area, etching the exposed two-dimensional material to expose the ultraviolet absorption layer and form steps;
[0008] A metal film is deposited on the bottom of a single-crystal substrate to form an electrode, followed by annealing to form the bottom electrode.
[0009] Photoresist is spin-coated onto the top surface of the device to expose the pattern using a UV mask. After development and removal of the photoresist, the top square electrode pattern is exposed. A metal film is then deposited on the surface, and the top electrode is formed after gold removal and photoresist removal.
[0010] Further, the substrate containing the lightly doped n-type gallium nitride epitaxial layer is cleaned, including:
[0011] The sample was ultrasonically cleaned in ethanol for at least 10 minutes at an ultrasonic frequency of 50–70 kHz.
[0012] Ultrasonic cleaning in acetone for at least 10 minutes at an ultrasonic frequency of 50–70 kHz;
[0013] Ultrasonic cleaning in isopropanol for at least 10 minutes at an ultrasonic frequency of 50–70 kHz.
[0014] Rinse repeatedly in a beaker of deionized water, then rinse with running water.
[0015] Dry it with nitrogen gas.
[0016] Furthermore, a three-zone tubular furnace was used to deposit a p-type two-dimensional material layer, MoxRe. 1-x The condition for S2 is:
[0017] The precursors used were sulfur powder and ReO3 + 0.003gMoO3, which were placed in the first and third temperature zones respectively. The highest temperature in the first temperature zone was 200-235℃, and the highest temperature in the third temperature zone was 650-850℃. The argon gas flow rate was 100-120sccm.
[0018] Furthermore, the thickness of the single-crystal substrate is 200-300 μm.
[0019] Furthermore, the lightly doped n-type gallium nitride epitaxial layer was grown using MOCVD or HVPE, with a carrier concentration of 5–8 x 10⁻⁶. 15 cm -3 The thickness is approximately 10–15 μm.
[0020] Furthermore, the p-type two-dimensional material layer Mo x Re 1-x The thickness of S2 is approximately 1-2 nm.
[0021] Further, the metal material used by the bottom electrode is Ti / Al / Ni / Au.
[0022] Further, the metal material used by the top electrode is Cr / Au, Ti / Al or Ti / Ni.
[0023] Further, the p-type two-dimensional material is Nb, Ta doped MoS2, Nb, Ta, W doped ReS2, V doped WSe2, multi-layer WSe2, ReSe2 or Sb doped In2Se3.
[0024] Further, the single crystal substrate is a heavily doped n-type self-supporting gallium nitride single crystal substrate or a SiC substrate.
[0025] The beneficial effects of the embodiment of the present application are: the 2D / 3D PN heterojunction reduces the reverse leakage, the vertical structure effectively reduces the photo-generated carrier recombination caused by surface effect and defects, and has a lower dark current; the weak p-type two-dimensional material obtained by the chemical vapor deposition doping method forms a junction region with the lightly doped n-type gallium nitride epitaxial layer, forms a built-in electric field, the staggered arrangement of the II-type energy band promotes the separation of the photo-generated carriers, and the device has a high rectification ratio and a high photo-on light ratio; and thanks to the absorption characteristics of gallium nitride and 2D material in the ultraviolet and visible light range, the detection of a wide spectrum range from ultraviolet to visible light can be realized. BRIEF DESCRIPTION OF DRAWINGS
[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0027] Figure 1 A preparation process schematic diagram of a mixed-dimensional heterojunction photodiode based on a gallium nitride single crystal substrate is provided for the embodiment of the present application.
[0028] Figure 2 A structure schematic diagram of a mixed-dimensional heterojunction photodiode is provided for the embodiment of the present application.
[0029] Figure 3 A photoelectric test I-V curve of a mixed-dimensional heterojunction photodiode is provided for the embodiment of the present application. DETAILED DESCRIPTION
[0030] In order to make those skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application.
[0031] This invention provides a method for fabricating a mixed-dimensional heterojunction photodiode based on a gallium nitride single-crystal substrate, comprising:
[0032] Step 1: Epitaxially grow a lightly doped n-type gallium nitride epitaxial layer on a single crystal substrate, polish both sides, clean, and blow dry;
[0033] The embodiments of the present invention further include: cleaning the substrate containing a lightly doped n-type gallium nitride epitaxial layer, including: ultrasonic cleaning in ethanol for at least 10 minutes at an ultrasonic frequency of 50-70 kHz; ultrasonic cleaning in acetone for at least 10 minutes at an ultrasonic frequency of 50-70 kHz; ultrasonic cleaning in isopropanol for at least 10 minutes at an ultrasonic frequency of 50-70 kHz; rinsing multiple times in a beaker of deionized water and rinsing with running water; and drying it with nitrogen gas.
[0034] Specifically, the single-crystal substrate is a heavily doped n-type self-supporting gallium nitride single-crystal substrate with a thickness of 200-300 μm. Preferably, a double-sided polished n-type heavily doped self-supporting gallium nitride substrate with a thickness of approximately 200 μm to 300 μm is selected, with 200 μm being the most preferred.
[0035] Furthermore, the lightly doped n-type gallium nitride epitaxial layer was grown using MOCVD or HVPE, with a carrier concentration of 5–8 x 10⁻⁶. 15 cm -3 The thickness is approximately 10–15 μm, preferably 12 μm.
[0036] Step 2: Deposit a p-type two-dimensional material layer Mo on the device surface using a three-temperature zone tube furnace. x Re 1-x S2, spin-coating photoresist, performing mask exposure pattern, developing and removing the photoresist to expose the two-dimensional material of the patterned area, etching the exposed two-dimensional material to expose the ultraviolet absorption layer and form steps;
[0037] MoxRe, a p-type two-dimensional material layer, was deposited using a three-zone tubular furnace. 1-x The conditions for S2 are as follows: Sulfur powder and ReO3 + 0.003g MoO3 are used as precursors, placed in the first and third temperature zones respectively. The highest temperature in the first temperature zone is 200-235℃, and the highest temperature in the third temperature zone is 650-850℃. The argon gas flow rate is 100-120 sccm. p-type two-dimensional material layer Mo x Re 1-x The thickness of S2 is approximately 1-2 nm, preferably 2 nm. The p-type two-dimensional material can also be: Nb or Ta-doped MoS2, Nb or Ta-doped ReS2, V-doped WSe2, multilayer WSe2, ReSe2, or Sb-doped ln2Se3.
[0038] Step three, evaporate metal film at the bottom of the single crystal substrate, anneal after forming electrode, form bottom electrode;
[0039] Step four, spin coating photoresist on the top surface of the device, UV mask exposure pattern, develop and remove photoresist, expose the top square electrode pattern, evaporate metal film on the surface, lift off after forming top electrode.
[0040] Specifically, the metal material used for the bottom electrode is Ti / Al / Ni / Au. The metal material used for the top electrode is Cr / Au, Ti / Al or Ti / Ni.
[0041] The application provides a preparation method of a mixed-dimensional heterojunction photodiode based on a gallium nitride single crystal substrate. A 2D / 3D PN heterojunction reduces reverse leakage, a vertical structure effectively reduces the recombination of photo-generated carriers caused by surface effects and defects, has lower dark current, and the weak p-type two-dimensional material obtained through chemical vapor deposition doping forms a junction area with a lightly doped n-type gallium nitride epitaxial layer, forms a built-in electric field, staggered arrangement of type II energy bands promotes the separation of photo-generated carriers, and the device has high rectification ratio and high photo-on light ratio. With the absorption characteristics of wide-bandgap semiconductor gallium nitride and 2D material to ultraviolet and visible light, the device can realize detection in a wide spectral range from ultraviolet to visible light.
[0042] An embodiment of the application is shown in Figure 1 The specific steps are as follows:
[0043] 1. Prepare a piece of heavily doped n-type self-supporting gallium nitride single crystal substrate, and epitaxially grow a 10-12 mu m lightly doped n-type gallium nitride epitaxial layer on the substrate by MOCVD or HVPE. After double-sided polishing, the substrate with the lightly doped n-type gallium nitride epitaxial layer is cleaned, that is, ultrasonic cleaning in ethanol for 10 minutes, the ultrasonic frequency is 50-70 KHz; ultrasonic cleaning in acetone for 10 minutes, the ultrasonic frequency is 50-70 KHz; ultrasonic cleaning in isopropyl alcohol for 10 minutes, the ultrasonic frequency is 50-70 KHz; rinse several times in a beaker of deionized water, and rinse with running water; dry with nitrogen.
[0044] 2. Deposit a p-type two-dimensional material layer MoxRe1-xS2, use a three-temperature zone tube furnace, the precursors are 0.75g of sulfur powder and 0.12g of ReO3+0.003g of MoO3, which are respectively placed in the first and third temperature zones, the highest temperature of the first temperature zone is 235 DEG C, the highest temperature of the third temperature zone is 750 DEG C, and the argon gas flow is 110sccm.
[0045] 3. Spin coating photoresist, mask exposure pattern, develop and remove photoresist, expose the patterned two-dimensional material.
[0046] 4. Dry etching is performed using Cl2 / SiCl4 to etch away the exposed two-dimensional material layer, thereby exposing the GaN ultraviolet absorption layer and forming a step. The etching depth is measured using an atomic force microscope.
[0047] 5. Preparation of bottom electrode: Metal film (such as Ti (25nm) / Al (75nm) / Ni (25nm) / Au (75nm)) is deposited by thermal evaporation, magnetron sputtering or electron beam evaporation, etc. After forming the electrode, it is annealed at 750℃ in N2 environment.
[0048] 6. Spin-coat photoresist, expose the pattern with ultraviolet mask, develop and remove the photoresist to expose the top square electrode pattern.
[0049] 7. Preparation of top electrode: A metal film of Cr (5nm) / Au (50nm) is deposited by thermal evaporation, magnetron sputtering or electron beam evaporation, and the gold is peeled off to form the top electrode.
[0050] This invention proposes a mixed-dimensional heterojunction vertical photodiode based on a gallium nitride single-crystal substrate, such as... Figure 2 As shown, it includes a gallium nitride single crystal substrate 1, a lightly doped n-type GaN epitaxial layer 2, a p-type two-dimensional material 3, top electrodes 4 / 5 / 6 / 7, and a bottom electrode 8: wherein, top electrodes 4 and 5 are placed on the p-type two-dimensional material layer 3, and top electrodes 6 and 7 are placed on the lightly doped n-type GaN epitaxial layer 2.
[0051] like Figure 3 The image shows the IV curves for testing the photoelectric performance of the fabricated mixed-dimensional heterojunction photodiode. Specifically, under 365nm ultraviolet light irradiation, the vertical 2D / 3D mixed-dimensional heterojunction photodiode exhibits a performance exceeding 10... 7 High rectification ratio, approximately 10 6 Its high on / off ratio and normalized detectivity exceeding 10¹⁴ Jones outperform other similar devices.
[0052] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
[0053] The above description is only a partial embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a mixed-dimensional heterojunction photodiode of a gallium nitride single crystal substrate, comprising: epitaxially growing a lightly doped n-type gallium nitride epitaxial layer on a gallium nitride single crystal substrate, polishing both sides, washing, and blowing dry; A p-type two-dimensional material layer Mo is deposited on the surface of the device by using a three-temperature-zone tube furnace x Re 1-x S2, spin coating photoresist, mask exposure pattern, develop photoresist, expose two-dimensional material in the pattern part, etch the exposed two-dimensional material to expose the gallium nitride ultraviolet absorption layer and form a step; evaporating a metal film on the bottom of the single crystal substrate, annealing after forming an electrode, and forming a bottom electrode; In the device top surface spin coating photoresist for ultraviolet mask exposure pattern, development, exposed to the top square electrode pattern, evaporation of metal film on the surface, gold after lifting the development of the top electrode; wherein, the top electrode includes four, two said top electrode is placed in the p-type two-dimensional material layer Mo x Re 1-x S2 above, another two said top electrode is placed on the lightly doped n-type gallium nitride epitaxial layer.
2. The production method according to claim 1, characterized by, washing the substrate containing the lightly doped n-type gallium nitride epitaxial layer, comprising: ultrasonic cleaning in ethanol for at least 10 min, with an ultrasonic frequency of 50-70 KHz; ultrasonic cleaning in acetone for at least 10 min, with an ultrasonic frequency of 50-70 KHz; ultrasonic cleaning in isopropyl alcohol for at least 10 min, with an ultrasonic frequency of 50-70 KHz; washing in a beaker of deionized water for multiple times, and washing with running water; blowing dry with nitrogen.
3. The preparation method according to claim 1, characterized in that, Depositing a p-type two-dimensional material layer MoxRe using a three-temperature-zone tube furnace 1-x The conditions at S2 are: The precursors are 0.75 g of sulfur powder and 0.012 g of ReO3+0.003 g of MoO3, which are placed in the first and third temperature zones, respectively, wherein the maximum temperature of the first temperature zone is 200-235°C, the maximum temperature of the third temperature zone is 650-850°C, and the argon flow rate is 100-120 sccm.
4. The preparation method according to claim 1, characterized in that, The thickness of the single crystal substrate is 200-300 μm.
5. The preparation method according to claim 1, characterized in that, The MOCVD or HVPE is used in the deposition of the light-doped n-type gallium nitride epitaxial layer, the carrier concentration is 5-8x10 15 cm -3 , and the thickness is 10-15 μm.
6. The method of claim 1, wherein, p-type two-dimensional material layer Mo x Re 1-x The thickness of S2 is 1-2 nm.
7. The preparation method according to claim 1, characterized in that, The metal material used for the bottom electrode is Ti / Al / Ni / Au.
8. The method of claim 1, wherein, The metal material used for the top electrode is Cr / Au, Ti / Al, or Ti / Ni.
9. The method of claim 1, wherein, The gallium nitride single crystal substrate is a heavily doped n-type self-supporting gallium nitride single crystal substrate.