Bias voltage adjustable photoelectric detector and preparation method and application thereof

Abstract

The invention relates to the field of semiconductor heterojunction photoelectric detectors, in particular to a bias voltage adjustable photoelectric detector and a preparation method and application thereof.The detector sequentially comprises a substrate, a buffer layer, a p-type wide bandgap semiconductor layer and a p-type narrow bandgap semiconductor layer from bottom to top, the p-type narrow bandgap semiconductor layer partially covers the p-type wide bandgap semiconductor layer, and the p-type narrow bandgap semiconductor layer covers the p-type narrow bandgap semiconductor layer. The detector further comprises a first metal electrode and a second metal electrode, the first metal electrode is arranged on the p-type wide bandgap semiconductor layer, the second metal electrode is arranged on the p-type narrow bandgap semiconductor layer, the first metal electrode does not make contact with the p-type narrow bandgap semiconductor layer, and the second metal electrode does not make contact with the p-type narrow bandgap semiconductor layer. The forbidden band width of the p-type wide forbidden band semiconductor layer ranges from 3.1 eV to 5 eV, and the forbidden band width of the p-type narrow forbidden band semiconductor layer ranges from 0.3 eV to 1.2 eV. The prepared detector is high in sensitivity, low in power consumption and simple in structure, and can be applied to photoelectric detection.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor heterojunction photoelectric detectors, and in particular to a bias-adjustable photoelectric detector and a preparation method and application thereof. Background Art

[0002] In the early 21st century, group III nitride materials have been greatly developed. Among them, aluminum gallium nitride (AlGaN) is a direct bandgap ternary compound semiconductor. Its bandgap can be continuously adjusted from 3.4eV (GaN) to 6.2eV (AlN) by changing the amount of Al element doped. It can cover the wavelength range of 200-365nm and has a high electron mobility (~2000cm 2 V -1 s -1 ), high breakdown electric field (~3MV / cm), high temperature resistance, and radiation resistance, making it an ideal ultraviolet detection material. However, the current mature infrared detection materials such as mercury cadmium telluride (HgCdTe), indium telluride (InSb), gallium arsenide (GaAs), etc., cannot be epitaxially grown on the same substrate with GaN due to lattice matching problems, so it is impossible to achieve a monolithic integrated ultraviolet-infrared wide-spectrum detector. Furthermore, due to the large difference in the band gap between ultraviolet detection materials and infrared detection materials, it is difficult to form a good energy band match. The interface barrier seriously hinders the collection of photogenerated carriers in narrow bandgap materials, resulting in a very weak infrared response. These problems have seriously hindered the application and development of ultraviolet-infrared wide-spectrum detectors.

[0003] Furthermore, current commercial photodetectors usually have a fixed spectral response range, and their accuracy in identifying detected targets is easily disturbed by the environment, especially in modern military battlefields with complex backgrounds and much interference. Therefore, there is an urgent need to develop photodetectors with adjustable spectral response ranges. In recent years, with the rise of low-dimensional materials and the advancement of nanotechnology, bias-adjustable photodetectors have made many outstanding research advances (ACS Photonics, 2021, DOI: 10.1021 / acsphotonics.1c00617; ACS Nano, 2023, DOI: 10.1021 / acsnano.3c02617; Nature Electronics, 2024, DOI: 10.1038 / s41928-024-01208-x). However, most of the bias-adjustable photodetectors reported so far are based on complex double heterojunction structures, which have strict restrictions on the thickness, doping concentration and band matching of the detection material, and the preparation process is complicated. These factors severely restrict its applicability. Molybdenum ditelluride (MoTe2) and tellurium selenide (Te x Se 1- x ) is an emerging semiconductor material with a bandgap width (0.35-1.9 eV) that can be continuously adjusted by changing the composition. In addition, these emerging semiconductor materials have a low melting point (<450°C), which is suitable for low-temperature thermal evaporation technology to achieve large-scale heterogeneous integration, bringing new opportunities for the development of high-performance photodetectors. Summary of the invention

[0004] In order to solve the above problems currently encountered by photodetectors, the present invention proposes a photodetection method based on adjustable bias. The method is based on a semiconductor heterojunction made of a deposited p-type wide bandgap semiconductor film and a deposited p-type narrow bandgap semiconductor film, and uses an external bias to adjust the heterojunction interface barrier height and carrier transport direction to achieve ultraviolet-infrared wide spectrum detection. It has high sensitivity and low power consumption, and solves the current technical problems of being unable to achieve monolithic integrated ultraviolet-infrared wide spectrum detection, poor ultraviolet and infrared responsivity, complex photodetector structure, cumbersome preparation process, and high manufacturing cost.

[0005] According to a first aspect of the present invention, a bias-adjustable photodetector is provided, wherein the detector comprises, from bottom to top, a substrate, a buffer layer, a p-type wide bandgap semiconductor layer, and a p-type narrow bandgap semiconductor layer, wherein the p-type narrow bandgap semiconductor layer partially covers the p-type wide bandgap semiconductor layer, and the detector further comprises a first metal electrode and a second metal electrode, wherein the first metal electrode is arranged on the p-type wide bandgap semiconductor layer, and the second metal electrode is arranged on the p-type narrow bandgap semiconductor layer, and the first metal electrode does not contact the p-type narrow bandgap semiconductor layer, and the bandgap width of the p-type wide bandgap semiconductor layer is 3.1 to 5 eV, and the bandgap width of the p-type narrow bandgap semiconductor layer is 0.3 to 1.2 eV.

[0006] Preferably, the material of the p-type wide bandgap semiconductor layer is selected from p-type doped GaN, p-type doped AlGaN, and p-type doped ZnO.

[0007] Preferably, the material of the p-type narrow bandgap semiconductor layer is selected from Te x Se 1-x , MoTe2, where Te x Se 1-x The value range of x is 0.2-0.8.

[0008] Preferably, the buffer layer material is AlN, with a thickness of 500-1000 nm; the p-type wide bandgap semiconductor layer has a thickness of 200-700 nm; and the p-type narrow bandgap semiconductor layer has a thickness of 100-400 nm.

[0009] Preferably, the substrate is a sapphire substrate; the first metal electrode is a nickel-gold alloy electrode, and the second metal electrode is a gold electrode; the thickness of the first metal electrode and the second metal electrode ranges from 50 to 100 nm.

[0010] According to another aspect of the present invention, a method for preparing the bias-adjustable photodetector is provided, comprising the following steps:

[0011] (1) epitaxially growing a buffer layer on a substrate;

[0012] (2) epitaxially growing a p-type wide bandgap semiconductor layer on the buffer layer;

[0013] (3) etching the p-type wide bandgap semiconductor layer using an inductively coupled plasma etching technique;

[0014] (4) using low-temperature thermal evaporation technology to control the low-temperature thermal evaporation temperature to 350-400° C., and depositing a p-type narrow bandgap semiconductor layer on the surface of the p-type wide bandgap semiconductor layer;

[0015] (5) Using electron beam evaporation technology, a first metal electrode is deposited on the surface of the p-type wide bandgap semiconductor layer, and a second metal electrode is deposited on the surface of the p-type narrow bandgap semiconductor layer.

[0016] Preferably, the buffer layer is epitaxially grown on the substrate, and the technology used for epitaxially growing the p-type wide bandgap semiconductor layer on the buffer layer is selected from metal organic chemical vapor deposition technology, molecular beam epitaxy technology, and hydride vapor phase epitaxy technology.

[0017] According to another aspect of the present invention, a method for using the detector for photoelectric detection is provided, wherein the detector can achieve:

[0018] i) Detection of ultraviolet light;

[0019] and / or ii) detection of a broad spectrum of ultraviolet and infrared light;

[0020] The specific steps of detecting ultraviolet light are as follows: measuring the wavelength of the radiation source, when the wavelength of the radiation source is 200-365nm, irradiating the light source on the detector, at this time the energy of the photon is greater than the bandgap width of the p-type wide bandgap semiconductor layer, not applying a bias voltage to the detector or applying a positive bias voltage to the detector, the generated photogenerated carriers are separated to form a photocurrent under the action of a built-in electric field or an external positive bias voltage, so as to realize the detection of the intensity of ultraviolet light;

[0021] The specific steps for detecting the ultraviolet and infrared wide spectrum are: measuring the wavelength of the radiation light source, when the wavelength of the radiation light source is 200-1800nm, irradiating the light source on the detector, at this time the energy of the photon is greater than the bandgap width of the p-type narrow bandgap semiconductor layer and less than the bandgap width of the p-type wide bandgap semiconductor layer, applying a negative bias to the detector, and the photogenerated electrons and holes are separated under the action of the negative bias to form a photocurrent, thereby realizing the detection of the ultraviolet and infrared wide spectrum intensity.

[0022] Preferably, the voltage of the positive bias is below 5V; the voltage of the negative bias is -5 to -1V.

[0023] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0024] (1) The present invention utilizes the hole barrier formed at the interface between the p-type wide bandgap semiconductor and the p-type narrow bandgap semiconductor to block the photogenerated holes generated by the p-type narrow bandgap semiconductor, and further controls the transport direction of the photogenerated carriers by changing the polarity of the external bias voltage, thereby realizing bias-adjustable ultraviolet-infrared wide spectrum detection. When zero bias is applied, the photogenerated electron-hole pairs generated by ultraviolet light can be smoothly collected by the electrode, while the photogenerated holes generated by visible and infrared light are blocked by the valence band barrier. At this time, the device is in the ultraviolet light detection mode; when a negative bias is applied, the interface barrier is lowered so that the electrons generated by low-energy photons can overcome the barrier height and be collected by the electrode, generating a photogenerated current. At this time, the device is in the ultraviolet-infrared wide spectrum detection mode.

[0025] (2) The present invention realizes the function of adjustable bias in the response band by using only a single heterojunction through band structure design, while the traditional double heterojunction bias-adjustable photodetector is usually composed of two heterojunctions composed of three different semiconductor materials. Therefore, the device of the present invention has the advantages of simple structure, simple manufacturing process and low cost.

[0026] (3) The present invention is based on a semiconductor heterostructure of van der Waals heterogeneous integration, and utilizes low-temperature thermal evaporation technology to control the low-temperature thermal evaporation temperature to 350-400°C, thereby achieving high-quality heterogeneous integration of p-type wide bandgap semiconductors and p-type narrow bandgap semiconductors, avoiding the stringent conditions of lattice matching in traditional heteroepitaxial growth, thereby effectively reducing the introduction of defects and dislocations, and ensuring excellent detection performance, achieving an ultraviolet responsivity of 0.96A / W and an infrared responsivity of 0.58A / W.

[0027] (4) The bias-adjustable heterojunction photodetector of the present invention is based on the working principle of the photovoltaic effect. It can work normally without applying a bias voltage or applying a very small bias voltage under the action of a built-in electric field, and has the characteristics of low dark current and low power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of a photodetector with adjustable bias voltage according to Example 1 of the present invention.

[0029] Figure 2 Schematic diagram of the operation of the bias-adjustable photodetector according to Embodiment 2 of the present invention.

[0030] Figure 3 The following are working energy band diagrams of the bias-adjustable photodetector of the present invention under different bias voltages, a is positive bias voltage, b is negative bias voltage.

[0031] Figure 4 Graphs showing normalized spectral response of the detector in Example 2 at bias voltages of -2 and +2 V, respectively.

[0032] Figure 5 This is a curve showing how the responsivity of the detector under a -2V bias voltage varies with the wavelength of the incident light in Example 3.

[0033] In the figure: 1. substrate, 2. buffer layer, 3. p-type wide bandgap semiconductor layer, 4. p-type narrow bandgap semiconductor layer, 5. first metal electrode, 6. second metal electrode. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The present invention proposes a bias-adjustable photodetector and a preparation method, which realizes the application of semiconductor heterojunction structure in the field of ultraviolet-infrared wide spectrum detection. The present invention introduces semiconductor heterojunction and its photovoltaic effect into the detection structure. The detector structure is based on semiconductor heterojunction, and uses the built-in electric field or external bias voltage of the semiconductor heterojunction interface to drive the transport of photogenerated carriers to complete the conversion of optical signals to electrical signals at room temperature, which can realize high-sensitivity and low-power ultraviolet-infrared wide spectrum photoelectric detection of the detector.

[0036] Example 1

[0037] The present invention proposes a method for preparing a photoelectric detector with adjustable bias voltage, which specifically comprises the following steps:

[0038] (1) Selection of substrate 1: 2-inch sapphire is selected as substrate 1 with a thickness of 430 μm.

[0039] (2) Growth of buffer layer 2: Aluminum nitride (AlN) buffer layer 2 with a thickness of 1 micron was grown on sapphire substrate 1 using metal organic chemical vapor deposition (MOCVD) technology. Trimethylaluminum (TMAl) and ammonia (NH3) were used as Al source and N source, respectively. The growth pressure of the reaction chamber was set to 50 torr, and the N source was continuously introduced into the reaction chamber, wherein the NH3 flow rate was constant at 62461 μmol / min, the TMAl flow rate was 13 μmol / min, and the molar ratio of group V elements to group III elements in the reaction chamber was maintained at 48:1.

[0040] (3) Growth of p-type wide bandgap semiconductor layer 3: A gallium nitride (GaN) film with a thickness of 700 nm was grown on the AlN buffer layer 2 using MOCVD technology and was doped with Mg. Trimethylgallium (TMGa), ammonia (NH3) and bismuth magnesium cyclopentadienyl (MgCp2) were used as Al source, N source and Mg source, respectively. The growth pressure of the reaction chamber was set to 50 torr, and the N source was continuously introduced into the reaction chamber. The flow rate of NH3 was constant at 62461 μmol / min, and the flow rate of TMGa was 30 μmol / min. The molar ratio of the V group element to the III group element introduced into the reaction chamber was 2045, thereby preparing a p-type GaN film.

[0041] (4) Etching of P-type GaN film: First, a periodic array pattern was prepared on the GaN film 3 using maskless lithography technology, and then the GaN film was etched into a periodic array structure using inductively coupled plasma (ICP) etching technology. The etching gas was a chlorine / boron trichloride (Cl2 / BCl3) mixed gas. The temperature of the reaction chamber was set to 20°C, the Cl2 flow rate was constant at 10 sccm, the BCl3 flow rate was constant at 15 sccm, and the etching time was 2 min 55 s.

[0042] (5) Growth of p-type narrow bandgap semiconductor layer 4: Using maskless lithography and low-temperature thermal evaporation technology, tellurium selenide alloy (TeSe) is accurately deposited on the etched P-type GaN film. x Se 1-x ) film with a thickness of 300 nm, using Se powder and Te powder as Se source and Te source respectively, and the vacuum degree of the evaporation chamber is 1.5×10 -4 The evaporation rates of Pa, Se and Te sources are and The mass ratio of Se source to Te source is about 0.66:1. Then a thermal annealing treatment at 240°C is performed in a nitrogen atmosphere to improve the film crystal quality to deposit Te on the P-type GaN film. x Se 1-x film.

[0043] (6) Preparation of the first metal electrode 5: An electrode pattern with a specific pattern structure is obtained by maskless lithography technology, and then a nickel metal layer and a gold metal layer are deposited by electron beam evaporation technology with thicknesses of 20 nanometers and 30 nanometers, respectively. Finally, a rapid thermal annealing treatment is performed in an air atmosphere to form a good ohmic contact. The annealing temperature is 700°C and the annealing time is 10 minutes. The prepared nickel-gold alloy electrode is used as the electrode of the p-type GaN film.

[0044] Preparation of the second metal electrode 6: The electrode pattern with a specific pattern structure is obtained by maskless photolithography, and then a gold metal layer with a thickness of 50 nanometers is deposited by electron beam evaporation technology. The prepared gold electrode is used as Te x Se 1-x Thin film electrodes.

[0045] Example 2

[0046] The present invention proposes a method for using a bias-adjustable photoelectric detector for ultraviolet-infrared wide-spectrum photoelectric detection, which specifically includes the following steps:

[0047] (1) irradiating the detector prepared in Example 1 with a monochromatic light source with adjustable wavelength, and using a semiconductor analyzer to provide a bias voltage for the detector;

[0048] (2) The output voltage of the semiconductor parameter analyzer is set to -2 V, and the wavelength of the radiation light of the adjustable monochromatic light source is scanned at the same time, with a scanning range of 200 to 1800 nm and a scanning step of 20 nm, and the photocurrent value generated by the detector at each wavelength is recorded;

[0049] (3) The output voltage of the semiconductor parameter analyzer is set to +2 V. The wavelength of the radiation light of the adjustable monochromatic light source is scanned at the same time. The scanning range is 200 to 360 nm, the scanning step is 20 nm, and the photocurrent value generated by the detector at each wavelength is recorded.

[0050] Figure 2 2 is a schematic diagram of the working of Example 2. When the device is working, when photons of a specific energy are irradiated, photogenerated electron-hole pairs are generated in the semiconductor heterojunction region, which are separated under the driving of or external bias to form a photogenerated current. At this time, a significant jump in the current can be observed by detecting the current passing through the two electrodes.

[0051] Figure 3 The working principle diagram of the present invention is shown in FIG. 1 . Under positive bias or zero bias ( Figure 3 In a), the photogenerated carriers excited by ultraviolet light in GaN can be collected by an external circuit to form photocurrent. However, Te x Se 1-xThe photogenerated holes in the detector will be blocked by the valence band barrier and eventually recombine with electrons from the external circuit and cannot be collected to form photocurrent. Therefore, under this condition, the detector cannot respond to Te x Se 1-x The absorbed radiation can only respond to the ultraviolet radiation absorbed by GaN, and its spectral response range only includes the ultraviolet region. Under negative bias ( Figure 3 b), the transmission direction of the photogenerated carriers is reversed, Te x Se 1-x The photogenerated carriers generated in GaN can be smoothly collected without potential barriers, thus achieving a wide UV-IR spectrum response.

[0052] Figure 4 It is a normalized spectral response curve diagram of the detector in Example 2 under -2 and +2V bias voltages respectively. It can be seen from the figure that when the bias voltage is -2V, the device has two response peaks near 360nm and 1060nm, showing an ultraviolet-infrared wide spectrum detection mode; when the bias voltage is +2V, the device light response is quickly cut off near 360nm, showing an ultraviolet detection mode.

[0053] Example 3

[0054] The present invention proposes a method for using a bias-adjustable photoelectric detector for ultraviolet-infrared wide-spectrum photoelectric detection, which specifically includes the following steps:

[0055] A monochromatic light source with radiation wavelengths of 365nm, 405nm, 520nm, 633nm, 830nm, 940nm, 1060nm, 1310nm and 1550nm is irradiated onto the detector prepared in Example 1, and a semiconductor analyzer is used to provide a bias voltage for the detector. The output voltage of the semiconductor parameter analyzer is set to -2V, and the photocurrent value generated by the detector at each wavelength is recorded.

[0056] Figure 5 The curve of the response of the detector under -2V bias in Example 3 as a function of the wavelength of the incident light shows that the device has response peaks at 365nm and 1060nm, which are 0.96A / W and 0.58A / W, respectively. It shows excellent ultraviolet-infrared wide-spectrum detection performance. The results show that the bias-adjustable photodetector of the present invention can realize wide-band detection from ultraviolet to infrared and can adjust its detection wavelength range by bias, thereby improving the practicality of semiconductor material photon detection devices.

[0057] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A photodetector with adjustable bias voltage, characterized in that: The detector comprises, from bottom to top, a substrate (1), a buffer layer (2), a p-type wide bandgap semiconductor layer (3), and a p-type narrow bandgap semiconductor layer (4), wherein the p-type narrow bandgap semiconductor layer (4) partially covers the p-type wide bandgap semiconductor layer (3). The detector further comprises a first metal electrode (5) and a second metal electrode (6), wherein the first metal electrode (5) is arranged on the p-type wide bandgap semiconductor layer (3), and the second metal electrode (6) is arranged on the p-type narrow bandgap semiconductor layer (4). The first metal electrode (5) is not in contact with the p-type narrow bandgap semiconductor layer (4), and the bandgap width of the p-type wide bandgap semiconductor layer (3) is 3.1 to 5 eV, and the bandgap width of the p-type narrow bandgap semiconductor layer (4) is 0.3 to 1.2 eV.

2. A bias-adjustable photodetector according to claim 1, characterized in that: The material of the p-type wide bandgap semiconductor layer (3) is selected from p-type doped GaN, p-type doped AlGaN, and p-type doped ZnO.

3. A bias-adjustable photodetector according to claim 2, characterized in that: The material of the p-type narrow bandgap semiconductor layer (4) is selected from Te x Se 1-x 、MoTe2,Te x Se 1-x The value range of x is 0.2~0.

8.

4. The bias-adjustable photodetector according to claim 3, characterized in that: The buffer layer (2) is made of AlN with a thickness of 500-1000 nm; the p-type wide bandgap semiconductor layer (3) has a thickness of 200-700 nm; and the p-type narrow bandgap semiconductor layer (4) has a thickness of 100-400 nm.

5. The bias-adjustable photodetector according to claim 4, characterized in that: The substrate (1) is a sapphire substrate; the first metal electrode (5) is a nickel-gold alloy electrode; the second metal electrode (6) is a gold electrode; the thickness of the first metal electrode (5) and the second metal electrode (6) ranges from 50 to 100 nm.

6. A method for preparing a bias-adjustable photodetector according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) epitaxially growing a buffer layer on a substrate; (2) epitaxially growing a p-type wide bandgap semiconductor layer on the buffer layer; (3) etching the p-type wide bandgap semiconductor layer using an inductively coupled plasma etching technique; (4) using low-temperature thermal evaporation technology to control the low-temperature thermal evaporation temperature to 350-400° C., and depositing a p-type narrow bandgap semiconductor layer on the surface of the p-type wide bandgap semiconductor layer; (5) Using electron beam evaporation technology, a first metal electrode is deposited on the surface of the p-type wide bandgap semiconductor layer, and a second metal electrode is deposited on the surface of the p-type narrow bandgap semiconductor layer.

7. A method for preparing a bias-adjustable photodetector as described in claim 6, wherein the technologies used for epitaxially growing a buffer layer on a substrate and epitaxially growing a p-type wide bandgap semiconductor layer on the buffer layer are selected from chemical vapor deposition technology, molecular beam epitaxy technology, and hydride vapor phase epitaxy technology.

8. A method for using the detector according to any one of claims 1 to 5 for photoelectric detection, characterized in that: The detector is capable of: i) Detection of ultraviolet light; and / or ii) detection of a broad spectrum of ultraviolet and infrared light; The specific steps of detecting ultraviolet light are as follows: measuring the wavelength of the radiation source, when the wavelength of the radiation source is 200-365nm, irradiating the light source on the detector, at this time the energy of the photon is greater than the bandgap width of the p-type wide bandgap semiconductor layer, not applying a bias voltage to the detector or applying a positive bias voltage to the detector, the generated photogenerated carriers are separated to form a photocurrent under the action of a built-in electric field or an external positive bias voltage, so as to realize the detection of the intensity of ultraviolet light; The specific steps for detecting the ultraviolet and infrared wide spectrum are: measuring the wavelength of the radiation light source, when the wavelength of the radiation light source is 200-1800nm, irradiating the light source on the detector, at this time the energy of the photon is greater than the bandgap width of the p-type narrow bandgap semiconductor layer and less than the bandgap width of the p-type wide bandgap semiconductor layer, applying a negative bias to the detector, and the photogenerated electrons and holes are separated under the action of the negative bias to form a photocurrent, thereby realizing the detection of the ultraviolet and infrared wide spectrum intensity.

9. A method for using the detector according to claim 8 for photoelectric detection, characterized in that: The voltage of the positive bias is below 5V; the voltage of the negative bias is -5 to -1V.

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