A double heterojunction self-powered ultraviolet photodetector and its preparation method
By introducing 2D semiconductors into traditional 3D semiconductor photodetectors and forming a dual heterojunction structure, the difficulty of selecting and growing 2D/3D longitudinal heterojunction devices in the prior art is solved, and the performance of high responsiveness, low dark current and self-driven ultraviolet photodetectors is achieved.
Patent Information
- Application Number
- CN202310060579.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-01-18
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2043-01-18
AI Technical Summary
The prior art is difficult to achieve the selection and growth of high-quality 2D/3D longitudinal heterojunction devices with excellent photoelectric performance, and the application of two-dimensional materials in the field of photoelectricity is limited by their weak absorbance and poor photogenerated carrier separation effects.
By introducing 2D semiconductors on the basis of traditional 3D semiconductor photodetectors, and adding a third layer of material to form a dual heterojunction structure, the molecular beam epitaxial method is used to grow 2H-MoTe2 films and 2D vdw semiconductor materials to form 2D/3D and 2D/2D heterojunctions, improving the photoelectric performance.
It achieves high responsiveness and low dark current to ultraviolet light, has self-driven phenomena and large detection light intensity range, and has performance exceeds that of traditional gallium nitride ultraviolet photodetectors, and solves the problem of device miniaturization.
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Figure CN115966632B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of semiconductor devices, and relates to a dual heterojunction self-powered photodetector for ultraviolet and a preparation method thereof. Background Art
[0002] Ultraviolet photodetectors are widely used in the fields of military, medical, aerospace, etc. Ultraviolet light is divided into many bands. Among them, ultraviolet light in the range of 320 - 400 nm is called the UVA band. This part of ultraviolet light has extremely strong penetration and can almost all reach the earth's surface, which may cause skin cancer. Therefore, the detection of ultraviolet light in this band is very important.
[0003] GaN is a third-generation wide-bandgap semiconductor, which has advantages such as a high absorption coefficient and good thermal stability, and is an ideal material for ultraviolet photodetectors. However, due to its large volume, it is difficult to make an integrated device. With the progress of technology, there is a growing pursuit of miniaturization, self-power supply, and flexibility of ultraviolet photodetectors. TMDC materials are 2D vdw materials, and their bandgap varies with the layer thickness, having many unprecedented advantages, such as high carrier mobility, low energy dissipation, low dark current, and adjustable optoelectronic properties, etc. However, due to the ultra-thin characteristics of two-dimensional materials, they have a weak light absorption rate and a poor separation effect on photo-generated carriers, which limits their application in the optoelectronic field. 2D / 3D heterojunctions can overcome these disadvantages, realize enhanced light absorption and separation of photo-generated carriers, and thus obtain a higher-performance ultraviolet photodetector. At present, the selection and growth of high-quality and excellent optoelectronic property 2D / 3D vertical heterojunction devices are still a difficult problem. Summary of the Invention
[0004] To solve the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a dual heterojunction self-powered ultraviolet photodetection device and a preparation method thereof. By introducing a 2D semiconductor on the basis of a traditional 3D semiconductor photodetector, an integrated device is realized, and the optoelectronic properties of such a device are improved by adding a third-layer material.
[0005] The present invention is realized by the following technical solutions.
[0006] On the one hand, the present invention provides a preparation method of a dual heterojunction self-powered ultraviolet photodetector, including:
[0007] Select a polished p-type or n-type GaN substrate, and fix the p-type or n-type GaN substrate on a sample holder;
[0008] Cover one side of the upper surface of the p-type or n-type GaN substrate with a tantalum sheet;
[0009] In an ultra-high vacuum environment, by means of molecular beam epitaxy, controlling the beam current ratio of Te to Mo and the growth temperature, a continuous 2H-MoTe2 thin film is grown on the upper surface of a p-type or n-type GaN substrate without shielding the tantalum sheet, forming a 2D / 3D heterojunction;
[0010] Shield one side of the upper surface of the continuously grown 2H-MoTe2 thin film with a tantalum sheet;
[0011] In an ultra-high vacuum environment, by means of molecular beam epitaxy, a third-layer 2D vdw semiconductor material is grown on the 2H-MoTe2 thin film without shielding the tantalum sheet, forming a 2D / 2D heterojunction;
[0012] Remove the tantalum sheets on the upper surface of the p-type or n-type GaN substrate and the 2H-MoTe2 thin film. By means of physical vapor deposition, a hollow mask template is attached to the upper surface of the p-type or n-type GaN substrate, the upper surface of the 2H-MoTe2 thin film, and the upper surface of the 2D vdw semiconductor material. An Au electrode is plated on the hollow mask template to obtain a double heterojunction self-driven ultraviolet photodetector.
[0013] Preferably, the width of the tantalum sheet shielding the p-type or n-type GaN substrate is 1 / 5 of the length of the p-type or n-type GaN substrate, and the width of the tantalum sheet shielding the 2H-MoTe2 thin film is 2 / 5 of the length of the p-type or n-type GaN substrate.
[0014] Preferably, in the ultra-high vacuum environment of the molecular beam epitaxy method, the vacuum degree is higher than 1×10 -6 Pa.
[0015] Preferably, the thickness of the 2H-MoTe2 thin film is 5 - 10 nm, the growth temperature is 340 - 350 °C; the beam current ratio of Te to Mo is 10:1 to 20:1.
[0016] Preferably, the 2D / 3D heterojunction is a heterojunction of a narrow-bandgap semiconductor and a wide-bandgap semiconductor.
[0017] Preferably, the third-layer 2D vdw semiconductor material is Te, MoS2, MoSe2, WTe2, WS2 or WSe2.
[0018] Preferably, the thickness of the third-layer 2D vdw semiconductor material is 5 - 10 nm.
[0019] Preferably, two Au electrodes are plated on the GaN substrate, four Au electrodes are plated on the 2H-MoTe2 thin film, and two Au electrodes are plated on the third-layer 2D vdw semiconductor material.
[0020] Preferably, the thickness of the Au electrode is 100 - 150 nm.
[0021] On the other hand, the present invention provides a double heterojunction self-driven ultraviolet photodetector prepared by the method described above.
[0022] Only the lower two heterojunctions of this device absorb light. Through the contact of 2D / 3D narrow-bandgap and wide-bandgap, the absorption of ultraviolet light around the 375nm band is realized. In addition, the lower two heterojunctions are type-II band contacts, and the large built-in electric field effectively promotes the separation of photo-generated carriers. Whether ultraviolet light is irradiated on the top or bottom of this device, it has a high responsivity and a low dark current, and has a self-driven effect at a 0V bias. In addition, this device has two output ports, which can be used to detect the light response signal. Through the measurement of the upper two heterojunctions, due to the higher mobility of the material and the adjustable transport path of photo-generated carriers, the separation of photo-generated carriers is promoted, the lifetime of photo-generated carriers is extended, and the light intensity range detected by the photodetector is improved. This ultraviolet detector can be applied to outdoor ultraviolet detection, etc.
[0023] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:
[0024] 1. Strong responsivity to ultraviolet light. Since the GaN-2H-MoTe2 is a heterojunction combined with a three-dimensional wide-bandgap and a two-dimensional narrow-bandgap semiconductor, the response to infrared and visible light is suppressed, and it only responds to ultraviolet light. Also, because a type-II band contact is formed, photo-generated carriers can be quickly separated.
[0025] 2. Low dark current. The three-dimensional wide-bandgap semiconductor and the two-dimensional narrow-bandgap semiconductor form a large built-in electric field, which promotes the separation of photo-generated carriers and limits the magnitude of the dark current.
[0026] 3. Self-driven phenomenon. At a 0V bias, there is a large on-off ratio for ultraviolet light, and it can be used as a self-driven device.
[0027] 4. Dual output ports. The light response output signal can be measured through both ends of GaN-MoTe2 and both ends of the MoTe2-2D vdw material.
[0028] 5. Large detection light intensity range. The upper two heterojunctions have a separation effect on the photo-generated carriers of the lower two heterojunctions. By applying a bias voltage to the upper two electrodes, the photo-generated electrons move in the upper circuit, restricting the recombination of photo-generated electrons and photo-generated holes, extending the lifetime of carriers, and preventing carriers from saturating even under strong or weak light. Description of the Drawings
[0029] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation to the present invention. In the drawings:
[0030] Figure 1 It is a schematic diagram of a double heterojunction self-driven ultraviolet photodetector;
[0031] Figures 2(a)-(j) are the preparation flow charts of double heterojunction self-driven ultraviolet photodetectors;
[0032] Figure 3 It is the energy band diagram of one kind of double heterojunction device p-type Te / n-type 2H-MoTe2 / p-type GaN;
[0033] Figure 4 For Example 1, in the dark and under 375 nm ultraviolet light with a light power of 19.2 mW / cm 2 It is the I-V image connecting electrode 1 and electrode 3 of the double heterojunction self-driven ultraviolet photodetector;
[0034] Figure 5 For Example 1, connecting electrode 6 and electrode 8 of the double heterojunction self-driven ultraviolet photodetector, irradiating with ultraviolet laser with a wavelength of 375 nm and a light power of 19.2 mW / cm 2 It is the I-t image measured by laser pulse under the illumination of light power. Detailed implementation manners
[0035] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. Here, the schematic embodiments of the present invention and the descriptions are used to explain the present invention, but do not limit the present invention.
[0036] As Figure 1 shown, a double heterojunction self-driven ultraviolet photodetector provided by an embodiment of the present invention includes a wide-bandgap semiconductor p-type or n-type GaN substrate, 2H-MoTe2 located on the p-type or n-type GaN substrate, and a third layer of 2D vdw semiconductor material located on the 2H-MoTe2. The p-type or n-type GaN substrate, the 2H-MoTe2 layer, and the third layer of 2D vdw semiconductor material layer are in a stepped structure, and Au electrodes are distributed on the upper surface of the stepped structure. There are a total of eight Au electrodes, including two on the third layer of vdw semiconductor material as the first electrode 1 and the second electrode 2, four on the 2H-MoTe2 as the third electrode 3, the fourth electrode 4, the fifth electrode 5, and the sixth electrode 6, and two on the GaN substrate as the seventh electrode 7 and the eighth electrode 8. The above-mentioned multiple electrodes are for improving the success rate of the device, and multiple groups of tests can be performed.
[0037] For the 2D vdw semiconductor material / 2H-MoTe2 / GaN three-layer device prepared by the present invention, since the upper two layers are both vdw materials, there is no need to consider lattice mismatch during growth. In the device, the 2H-MoTe2 / GaN heterojunction is a type-II energy band contact, and a large energy band bending will occur. After illumination, the photo-generated carriers are quickly separated under the action of the built-in electric field. The energy band diagram of the double heterojunction device p-type Te / n-type 2H-MoTe2 / p-type GaN can be seen in Figure 3As shown; when a third layer of material is added to the heterojunction, through the measurement of the upper two layers of materials, the separation of photo-generated carriers in the lower two-layer heterojunction can be promoted, the transport path of photo-generated carriers is changed, and the lifetime of photo-generated carriers can be extended. Therefore, the prepared double heterojunction self-driven ultraviolet photodetector has a very low dark current and a large on-off ratio, and can be used for self-driven devices. The performance of this device exceeds that of traditional gallium nitride ultraviolet photodetectors, and at the same time solves the difficulties such as device miniaturization.
[0038] The embodiment of the present invention also provides a preparation method of a double heterojunction self-driven ultraviolet photodetector, and the specific steps are as follows:
[0039] 1) Select a polished p-type or n-type 2-μm-thick GaN substrate with a doping concentration of 1×10 20 cm -3 , as shown in Fig. 2(a).
[0040] 2) Prepare two tantalum sheets. The width of tantalum sheet 1 is 1 / 5 of the length of the p-type or n-type GaN substrate, and the width of tantalum sheet 2 is 2 / 5 of the length of the p-type or n-type GaN substrate.
[0041] 3) Fix the p-type or n-type GaN substrate in step 1) on the sample holder, cover one side of the upper surface of the p-type or n-type GaN substrate with tantalum sheet 1, and weld both ends to the sample holder; arrange tantalum sheet 2 under the p-type or n-type GaN substrate, and weld one end to the sample holder first without covering the sample, as shown in Fig. 2(b).
[0042] 4) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, grow a continuous 2H-MoTe2 thin film on the upper surface of the p-type or n-type GaN substrate in step 3) by molecular beam epitaxy to form a 2D / 3D heterojunction. The 2D / 3D heterojunction is a heterojunction of a narrow-bandgap and a wide-bandgap semiconductor. See Fig. 2(c). The thickness of the 2H-MoTe2 thin film is 5-10 nm, the growth temperature is 340-350 °C, and the beam current ratio of Te to Mo is 10:1 to 20:1.
[0043] 5) In an ultra-high vacuum environment with a vacuum higher than ×10 -6 Pa, cover the pre-welded tantalum sheet 2 in step 3) on the upper surface of the 2H-MoTe2 close to the side of tantalum sheet 1, as shown in Fig. 2(d).
[0044] 6) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6In an ultra-high vacuum environment of 1×10 Pa, a third-layer 2D vdw semiconductor material is grown on 2H-MoTe2 in step 5) by molecular beam epitaxy to form a 2D / 2D heterojunction, as shown in Fig. 2(e). Keep warm for 10 min. The third-layer 2D vdw semiconductor material is Te, MoS2, MoSe2, WTe2, WS2 or WSe2, with a thickness of 5-10 nm.
[0045] 7) Remove tantalum sheet 1 and tantalum sheet 2, as shown in Fig. 2(f).
[0046] 8) Attach the self-made three-layer film hollow mask template to the upper surface of the sample prepared in step 6) by physical vapor deposition, as shown in Fig. 2(g);
[0047] 9) Deposit Au electrodes with a thickness of 100-150 nm on the three-layer film respectively. Deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third-layer 2D vdw semiconductor material, as shown in Fig. 2(h). Obtain a double heterojunction self-driven ultraviolet photodetector.
[0048] The preparation of the photodetector of the present invention will be further described below through different embodiments.
[0049] Example 1
[0050] 1) Select a polished p-type GaN substrate with a thickness of 2 μm and a doping concentration of 1×10 20 cm -3 ;
[0051] 2) Shield tantalum sheet 1 on one side of the upper surface of the p-type GaN substrate; the width of the tantalum sheet shielded on the p-type GaN substrate is 1 / 5 of the length of the p-type GaN substrate;
[0052] 3) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy method, control the beam current ratio of Te to Mo to be 18:1 and the growth temperature to be 350 °C, and grow a continuous 2H-MoTe2 thin film on the upper surface of the unshielded p-type GaN substrate, with a thin film thickness of 10 nm, to form a 2D / 3D heterojunction;
[0053] 4) Shield tantalum sheet 2 on one side of the upper surface of the grown continuous 2H-MoTe2 thin film; the width of the tantalum sheet shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the p-type GaN substrate;
[0054] 5) In a vacuum higher than 1×10 -6In an ultra-high vacuum environment of Pa, through molecular beam epitaxy, a third layer of 2D vdw semiconductor material is grown on a 2H-MoTe2 thin film without covering the tantalum sheet to form a 2D / 2D heterojunction; the third layer of 2D vdw semiconductor material is Te with a thickness of 5 nm;
[0055] 6) Remove tantalum sheet 1 and tantalum sheet 2. Through physical vapor deposition, a hollow mask template is attached to the upper surface of the p-type GaN substrate, the upper surface of the 2H-MoTe2 thin film, and the upper surface of the 2D vdw semiconductor material. An Au electrode with a thickness of 140 nm is deposited on the hollow mask template. Two Au electrodes are deposited on the GaN substrate, four Au electrodes are deposited on the 2H-MoTe2 thin film, and two Au electrodes are deposited on the third layer of 2D vdw semiconductor material to obtain a double heterojunction self-driven ultraviolet photodetector.
[0056] Connect electrode 1 - electrode 3 (or electrode 2 - electrode 4) to measure the Te / 2H-MoTe2 heterojunction. The dark current of the device is 3.2×10 -12 A, and the responsivity to ultraviolet light reaches 2.1×10 3 mA / W, the detectivity reaches 3×10 13 Jones, see Figure 4 , and the linear dynamic range reaches 120 dB.
[0057] Connect electrode 6 - electrode 8 (or electrode 5 - electrode 7) to measure the 2H-MoTe2 / p-type GaN heterojunction. There is no response under infrared and visible light, and the on / off ratio reaches 1.2×10 5 , see Figure 5 .
[0058] Example 2
[0059] 1) Select a polished p-type 2-μm-thick GaN substrate with a doping concentration of ×10 20 cm -3 ;
[0060] 2) Cover tantalum sheet 1 on one side of the upper surface of the p-type GaN substrate; the width of the tantalum sheet covering the p-type GaN substrate is 1 / 5 of the length of the p-type GaN substrate;
[0061] 3) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, through molecular beam epitaxy, control the beam current ratio of Te to Mo to be 20:1 and the growth temperature to be 345 °C, and grow a continuous 2H-MoTe2 thin film on the upper surface of the p-type GaN substrate without covering the tantalum sheet. The thickness of the thin film is 6 nm to form a 2D / 3D heterojunction;
[0062] 4) Shield the tantalum sheet 2 on one side of the upper surface of the continuously grown 2H-MoTe2 thin film; the width of the tantalum sheet shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the p-type GaN substrate;
[0063] 5) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, through molecular beam epitaxy, grow the third layer of 2D vdw semiconductor material on the 2H-MoTe2 thin film without shielding the tantalum sheet to form a 2D / 2D heterojunction; the third layer of 2D vdw semiconductor material is WTe2 with a thickness of 6 nm;
[0064] 6) Remove the tantalum sheet 1 and the tantalum sheet 2, and attach a hollow mask on the upper surface of the p-type GaN substrate, the upper surface of the 2H-MoTe2 thin film, and the upper surface of the 2D vdw semiconductor material by physical vapor deposition. Deposit an Au electrode with a thickness of 150 nm on the hollow mask, deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third layer of 2D vdw semiconductor material respectively to obtain a double heterojunction self-driven ultraviolet photodetector.
[0065] Connect electrode 1 - electrode 3 (or electrode 2 - electrode 4) to measure the WTe2 and 2H-MoTe2 heterojunction. The dark current of the device is 2.7×10 -12 A, and the responsivity to ultraviolet light reaches 2.3×10 3 mA / W, the detectivity reaches 3.4×10 13 Jones, and the linear dynamic range reaches 122 dB.
[0066] Connect electrode 6 - electrode 8 (or electrode 5 - electrode 7) to measure the 2H-MoTe2 and p-type GaN heterojunction. There is no response under infrared and visible light, and the on-off ratio reaches 1.4×10 5 .
[0067] Example 3
[0068] 1) Select a polished p-type 2-μm-thick GaN substrate with a doping concentration of 1×10 20 cm -3 ;
[0069] 2) Shield the tantalum sheet 1 on one side of the upper surface of the p-type GaN substrate; the width of the tantalum sheet shielded on the p-type GaN substrate is 1 / 5 of the length of the p-type GaN substrate;
[0070] 3) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6In an ultra-high vacuum environment of Pa, by means of molecular beam epitaxy, the beam current ratio of Te to Mo is controlled to be 15:1 and the growth temperature is 340 °C. A continuous 2H-MoTe2 thin film with a thickness of 5 nm is grown on the upper surface of a p-type GaN substrate without shielding tantalum foil, forming a 2D / 3D heterojunction;
[0071] 4) Shield tantalum foil 2 on one side of the upper surface of the continuously grown 2H-MoTe2 thin film; the width of the tantalum foil shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the p-type GaN substrate;
[0072] 5) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by means of molecular beam epitaxy, a third layer of 2D vdw semiconductor material is grown on the 2H-MoTe2 thin film without shielding tantalum foil, forming a 2D / 2D heterojunction; the third layer of 2D vdw semiconductor material is WS2 with a thickness of 10 nm;
[0073] 6) Remove tantalum foil 1 and tantalum foil 2, and by means of physical vapor deposition, attach a hollow mask template on the upper surface of the p-type GaN substrate, the upper surface of the 2H-MoTe2 thin film, and the upper surface of the 2D vdw semiconductor material. Deposit Au electrodes with a thickness of 100 nm on the hollow mask template, deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third layer of 2D vdw semiconductor material respectively, to obtain a double heterojunction self-powered ultraviolet photodetector.
[0074] Connect electrode 1 - electrode 3 (or electrode 2 - electrode 4) to measure the WS2 / 2H-MoTe2 heterojunction. The dark current of the device is 3.3×10 -12 A, and the responsivity to ultraviolet light reaches 3.7×10 3 mA / W, the detectivity reaches 4.2×10 13 Jones, and the linear dynamic range reaches 124 dB.
[0075] Connect electrode 6 - electrode 8 (or electrode 5 - electrode 7) to measure the 2H-MoTe2 / p-type GaN heterojunction. There is no response under infrared and visible light, and the on-off ratio reaches 1.1×10 5 .
[0076] Example 4
[0077] 1) Select a polished n-type 2-μm-thick GaN substrate with a doping concentration of 1×10 20 cm -3 ;
[0078] 2) Shield the tantalum sheet 1 on one side of the upper surface of the n-type GaN substrate; the width of the tantalum sheet shielded on the n-type GaN substrate is 1 / 5 of the length of the n-type GaN substrate;
[0079] 3) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy, control the beam current ratio of Te to Mo to be 10:1 and the growth temperature to be 350 °C, and grow a continuous 2H-MoTe2 thin film on the upper surface of the n-type GaN substrate without shielding the tantalum sheet. The thickness of the thin film is 7 nm to form a 2D / 3D heterojunction;
[0080] 4) Shield the tantalum sheet 2 on one side of the upper surface of the continuously grown 2H-MoTe2 thin film; the width of the tantalum sheet shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the n-type GaN substrate;
[0081] 5) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy, grow the third layer of 2D vdw semiconductor material on the 2H-MoTe2 thin film without shielding the tantalum sheet to form a 2D / 2D heterojunction; the third layer of 2D vdw semiconductor material is WSe2 with a thickness of 8 nm;
[0082] 6) Remove the tantalum sheet 1 and the tantalum sheet 2, and attach a hollow mask on the upper surface of the n-type GaN substrate, the upper surface of the 2H-MoTe2 thin film, and the upper surface of the 2D vdw semiconductor material by physical vapor deposition. Deposit an Au electrode with a thickness of 110 nm on the hollow mask, deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third layer of 2D vdw semiconductor material respectively to obtain a double heterojunction self-driven ultraviolet photodetector.
[0083] Connect electrode 1 - electrode 3 (or electrode 2 - electrode 4) to measure the WSe2 and 2H-MoTe2 heterojunction. The dark current of the device is 2.4×10 -12 A, and the responsivity to ultraviolet light reaches 1.9×10 3 mA / W, the detectivity reaches 2.2×10 13 Jones, and the linear dynamic range reaches 128 dB.
[0084] Connect electrode 6 - electrode 8 (or electrode 5 - electrode 7) to measure the 2H-MoTe2 and n-type GaN heterojunction. It has no response under infrared and visible light, and the on-off ratio reaches 1.7×10 5 .
[0085] Example 5
[0086] 1) Select a polished n-type GaN substrate with a thickness of 2 μm and a doping concentration of 1×1020 cm -3 ;
[0087] 2) Shield the tantalum sheet 1 on one side of the upper surface of the n-type GaN substrate; the width of the tantalum sheet shielded on the n-type GaN substrate is 1 / 5 of the length of the n-type GaN substrate;
[0088] 3) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy, control the beam current ratio of Te to Mo to be 12:1 and the growth temperature to be 350 °C, and grow a continuous 2H-MoTe2 thin film on the upper surface of the n-type GaN substrate without shielding the tantalum sheet. The thickness of the thin film is 8 nm to form a 2D / 3D heterojunction;
[0089] 4) Shield the tantalum sheet 2 on one side of the upper surface of the continuously grown 2H-MoTe2 thin film; the width of the tantalum sheet shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the n-type GaN substrate;
[0090] 5) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy, grow the third layer of 2D vdw semiconductor material on the 2H-MoTe2 thin film without shielding the tantalum sheet to form a 2D / 2D heterojunction; the third layer of 2D vdw semiconductor material is MoS2 with a thickness of 9 nm;
[0091] 6) Remove the tantalum sheet 1 and the tantalum sheet 2, and attach a perforated mask on the upper surface of the n-type GaN substrate, the upper surface of the 2H-MoTe2 thin film, and the upper surface of the 2D vdw semiconductor material by physical vapor deposition. Deposit an Au electrode with a thickness of 130 nm on the perforated mask, deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third layer of 2D vdw semiconductor material respectively to obtain a double heterojunction self-driven ultraviolet photodetector.
[0092] Connect electrode 1 - electrode 3 (or electrode 2 - electrode 4) to measure the MoS2 and 2H-MoTe2 heterojunction. The dark current of the device is 3.8×10 -12 A, and the responsivity to ultraviolet light reaches 4.2×10 3 mA / W, the detectivity reaches 3.4×10 13 Jones, and the linear dynamic range reaches 130 dB.
[0093] Connect electrode 6 - electrode 8 (or electrode 5 - electrode 7) to measure the 2H-MoTe2 and n-type GaN heterojunction. There is no response under infrared and visible light, and the on-off ratio reaches 1.0×10 5 .
[0094] Example 6
[0095] 1) Select a polished n-type 2-μm-thick GaN substrate with a doping concentration of 1×10 20 cm -3 ;
[0096] 2) Shield tantalum sheet 1 on one side of the upper surface of the n-type GaN substrate; the width of the tantalum sheet shielded on the n-type GaN substrate is 1 / 5 of the length of the n-type GaN substrate;
[0097] 3) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy, control the beam current ratio of Te to Mo to be 16:1 and the growth temperature to be 350 °C, and grow a continuous 2H-MoTe2 thin film with a thickness of 9 nm on the upper surface of the n-type GaN substrate without shielding the tantalum sheet to form a 2D / 3D heterojunction;
[0098] 4) Shield tantalum sheet 2 on one side of the upper surface of the grown continuous 2H-MoTe2 thin film; the width of the tantalum sheet shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the n-type GaN substrate;
[0099] 5) In an ultra-high vacuum environment with a vacuum higher than 1×10 -6 Pa, by molecular beam epitaxy, grow a third layer of 2D vdw semiconductor material on the 2H-MoTe2 thin film without shielding the tantalum sheet to form a 2D / 2D heterojunction; the third layer of 2D vdw semiconductor material is MoSe2 with a thickness of 7 nm;
[0100] 6) Remove tantalum sheet 1 and tantalum sheet 2, and by physical vapor deposition, attach a hollow mask on the upper surfaces of the n-type GaN substrate, the 2H-MoTe2 thin film, and the 2D vdw semiconductor material, and deposit Au electrodes with a thickness of 120 nm on the hollow mask, deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third layer of 2D vdw semiconductor material respectively to obtain a double heterojunction self-driven ultraviolet photodetector.
[0101] Connect electrode 1 - electrode 3 (or electrode 2 - electrode 4), measure the MoSe2 and 2H-MoTe2 heterojunction, the dark current of the device is 2.6×10 -12 A, the responsivity to ultraviolet light reaches 3.6×10 3 mA / W, the detectivity reaches 4.0×10 13 Jones, and the linear dynamic range reaches 124 dB.
[0102] Connect electrodes 6 - electrode 8 (or electrode 5 - electrode 7), measure the 2H - MoTe2 and n - type GaN heterojunction, which has no response under infrared and visible light, and the on - off ratio reaches 1.5×10 5 .
[0103] Next, test the double - heterojunction self - powered ultraviolet photodetector prepared in the embodiment.
[0104] Irradiate the top or bottom of the prepared device with ultraviolet light, and test multiple groups of electrodes on the upper and lower heterojunctions. Connect the positive electrode to the Au electrode on 2H - MoTe2 and the negative electrode to the Au electrode on the third - layer 2D vdw semiconductor material to test the upper two - layer heterojunction, as shown in Fig. 2(i). Connect the positive electrode to the Au electrode on 2H - MoTe2 and the negative electrode to the Au electrode on GaN to test the lower two - layer heterojunction, as shown in Fig. 2(j).
[0105] Photoresponse test:
[0106] First, connect the two - end electrodes of electrode 1 - electrode 2, electrode 3 - electrode 4, electrode 5 - electrode 6, and electrode 7 - electrode 8 in Figure 1 respectively, and test I - V respectively to determine that the electrodes are ohmic contacts.
[0107] Connect the two - end electrodes of electrode 1 - electrode 3 (or electrode 2 - electrode 4), electrode 6 - electrode 8 (or electrode 5 - electrode 7), and measure I - V under darkness and different light powers respectively.
[0108] Connect Figure 1 the two - end electrodes of electrode 1 - electrode 3 (or electrode 2 - electrode 4), electrode 6 - electrode 8 (or electrode 5 - electrode 7) in, irradiate with a 375 - nm ultraviolet laser under a 0V bias voltage, and measure the I - t image through laser pulses.
[0109] Specifically, connect electrode 1 - electrode 3 (or electrode 2 - electrode 4), and measure the I - V images under darkness and different light powers respectively. The dark current of the device reaches 10 -12 A, the responsivity to ultraviolet light reaches 10 3 mA / W, the detectivity reaches 10 13 Jones, and the linear dynamic range reaches 120 dB.
[0110] Connect electrode 6 - electrode 8 (or electrode 5 - electrode 7), which has no response under infrared and visible light, and the on - off ratio reaches 10 5 .
[0111] The double heterojunction self-powered ultraviolet photodetector prepared by the present invention belongs to high-quality heterojunctions and has a simple structure. By combining a traditional 3D wide-bandgap semiconductor and a 2D vdw narrow-bandgap semiconductor, the dark current is reduced, the light response intensity and the photodetection rate are improved, and there is a large on-off ratio. The dark current of the device is not higher than 3.8×10 -12 A, the responsivity to ultraviolet light reaches 4.2×10 3 mA / W, the detectivity reaches 4.2×10 13 Jones, and the linear dynamic range reaches 130 dB. The on-off ratio under ultraviolet light reaches 1.7×10 5 .
[0112] The present invention can achieve self-power supply and reduce energy consumption. The performance of the device exceeds that of traditional gallium nitride ultraviolet photodetectors, and at the same time makes up for the defects of the vdw material with weak light absorption rate and poor separation of photo-generated carriers, which helps to miniaturize the device. The present invention can detect ultraviolet light of about 375 nm and can be applied to outdoor ultraviolet light detection, etc.
[0113] The present invention is not limited to the above embodiments. Based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and deformations of some technical features without creative labor according to the disclosed technical content, and these substitutions and deformations are all within the protection scope of the present invention.
Claims
1. A method for preparing a double heterojunction self-driven ultraviolet photodetector, characterized in that, Including: Select a polished p-type or n-type GaN substrate and fix the p-type or n-type GaN substrate on a sample holder; Shield a tantalum sheet on one side of the upper surface of the p-type or n-type GaN substrate; In an ultra-high vacuum environment with a vacuum degree higher than 1×10 -6 Pa, by means of molecular beam epitaxy, controlling the beam current ratio of Te to Mo and the growth temperature, a continuous 2H-MoTe2 thin film is grown on the upper surface of a p-type or n-type GaN substrate without covering the tantalum sheet to form a 2D / 3D heterojunction; Shield a tantalum sheet on one side of the upper surface of the grown continuous 2H-MoTe2 thin film; In an ultra-high vacuum environment, by molecular beam epitaxy, grow a third layer of 2D vdw semiconductor material on the 2H-MoTe2 thin film where the tantalum sheet is not shielded. The third layer of 2D vdw semiconductor material is Te, MoS2, MoSe2, WTe2, WS2 or WSe2 to form a 2D / 2D heterojunction; Remove the tantalum sheets on the upper surfaces of the p-type or n-type GaN substrate and the 2H-MoTe2 thin film. By physical vapor deposition, attach a perforated mask template on the upper surface of the p-type or n-type GaN substrate, the upper surface of the 2H-MoTe2 thin film and the upper surface of the 2D vdw semiconductor material, and deposit Au electrodes on the perforated mask templates respectively to obtain a double heterojunction self-driven ultraviolet photodetector.
2. The method for preparing a double heterojunction self-driven ultraviolet photodetector according to claim 1, characterized in that, The width of the tantalum sheet shielded on the p-type or n-type GaN substrate is 1 / 5 of the length of the p-type or n-type GaN substrate, and the width of the tantalum sheet shielded on the 2H-MoTe2 thin film is 2 / 5 of the length of the p-type or n-type GaN substrate.
3. The method for preparing a double heterojunction self-driven ultraviolet photodetector according to claim 1, characterized in that, The thickness of the 2H-MoTe2 thin film is 5 - 10 nm, and the growth temperature is 340 - 350 °C; the beam current ratio of Te to Mo is 10:1 - 20:
1.
4. The method for preparing a double heterojunction self-driven ultraviolet photodetector according to claim 1, characterized in that, The 2D / 3D heterojunction is a heterojunction of a narrow-bandgap and a wide-bandgap semiconductor.
5. The method for preparing a double heterojunction self-driven ultraviolet photodetector according to claim 1, characterized in that, The thickness of the third layer of 2D vdw semiconductor material is 5 - 10 nm.
6. The method for preparing a double heterojunction self-driven ultraviolet photodetector according to claim 1, characterized in that, Deposit two Au electrodes on the GaN substrate, four Au electrodes on the 2H-MoTe2 thin film, and two Au electrodes on the third layer of 2D vdw semiconductor material respectively.
7. The method for preparing a double heterojunction self-driven ultraviolet photodetector according to claim 6, characterized in that, The thickness of the Au electrode is 100 - 150 nm.
8. A double heterojunction self-driven ultraviolet photodetector prepared by the method according to any one of claims 1-7.