A bias-adjustable photodetector, a preparation method and application thereof

Abstract

The application relates to the field of semiconductor heterojunction photodetectors, in particular to a bias-adjustable photodetector and a preparation method and application thereof. The photodetector is sequentially arranged from bottom to top as a substrate, a buffer layer, a p-type wide-bandgap semiconductor layer and a p-type narrow-bandgap semiconductor layer, the p-type narrow-bandgap semiconductor layer partially covers the p-type wide-bandgap semiconductor layer, the photodetector 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, the second metal electrode is arranged on the p-type narrow-bandgap semiconductor layer, the first metal electrode is not in contact with the p-type narrow-bandgap semiconductor layer, the bandgap width of the p-type wide-bandgap semiconductor layer is 3.1-5 eV, and the bandgap width of the p-type narrow-bandgap semiconductor layer is 0.3-1.2 eV. The prepared photodetector is high in sensitivity, low in power consumption, simple in structure and can be applied to photodetection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor heterojunction photodetectors, and in particular to a bias voltage adjustable photodetector and a preparation method and application thereof. BACKGROUND

[0002] In the early 21st century, III-nitride materials have been greatly developed. Aluminum gallium nitride (AlGaN) is a direct bandgap ternary compound semiconductor, whose bandgap can be continuously adjusted from 3.4 eV (GaN) to 6.2 eV (AlN) by changing the doping amount of Al element, covering a wavelength range of 200-365 nm, and has high electron mobility (~2000 cm 2 V -1 s -1 ), high breakdown field (~3 MV / cm), high temperature resistance, radiation resistance, etc., becoming an ideal ultraviolet detection material. However, the current mature infrared detection materials such as mercury cadmium telluride (HgCdTe), indium antimonide (InSb), and gallium arsenide (GaAs) cannot be epitaxially grown on the same substrate due to lattice matching problems, so single-chip integrated ultraviolet-infrared wide-spectrum detectors cannot be realized. Moreover, due to the large difference in bandgap between ultraviolet detection materials and infrared detection materials, it is difficult to form a good band matching. The interface barrier seriously hinders the collection of photo-generated carriers in narrow-bandgap materials, resulting in weak infrared response. These problems seriously hinder the application and development of ultraviolet-infrared wide-spectrum detectors.

[0003] Moreover, the current commercial photodetectors usually have a fixed spectral response range, and their accuracy in identifying detection targets is easily disturbed by the environment, especially in modern military battlefields with complex backgrounds and many disturbances. Therefore, there is an urgent need to develop photodetectors with adjustable spectral response range. In recent years, with the rise of low-dimensional materials and the progress of nanotechnology, bias voltage adjustable photodetectors have made many outstanding research progress (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 currently reported bias voltage adjustable photodetectors are based on complex double heterojunction structures, which have strict restrictions on the thickness, doping concentration and band matching of the detection materials, and the preparation process is complex. These factors seriously restrict their applicability. Molybdenum ditelluride (MoTe2) and tellurium selenide (Te x Se 1- x As a new semiconductor material, the band gap (0.35-1.9eV) of the new semiconductor material can be continuously adjusted by changing the composition, and in addition, the new semiconductor material has a low melting point (<450℃), which is suitable for large-scale heterojunction integration by low-temperature thermal evaporation technology, and brings new opportunities for the development of high-performance photodetectors. SUMMARY

[0004] In order to solve the above problems encountered by the photodetector at present, the application provides a bias-adjustable photodetection method. The method is based on a semiconductor heterojunction made of a p-type wide-bandgap semiconductor thin film deposited and grown and a deposited p-type narrow-bandgap semiconductor thin film. The height of the heterojunction interface barrier and the carrier transport direction are adjusted by an external bias to realize ultraviolet-infrared wide-spectrum detection, which has high sensitivity and low power consumption, and solves the technical problems of current ultraviolet-infrared wide-spectrum detection which cannot be realized by monolithic integration, poor ultraviolet and infrared responsivity, complex photodetector structure, complicated preparation process and high manufacturing cost.

[0005] According to a first aspect of the application, a bias-adjustable photodetector is provided, which 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. The p-type narrow-bandgap semiconductor layer partially covers the p-type wide-bandgap semiconductor layer. The photodetector 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, and the second metal electrode is arranged on the p-type narrow-bandgap semiconductor layer. The first metal electrode does not contact the p-type narrow-bandgap semiconductor layer. The band gap of the p-type wide-bandgap semiconductor layer is 3.1-5eV, and the band gap of the p-type narrow-bandgap semiconductor layer is 0.3-1.2eV.

[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, wherein the value of x is 0.2-0.8. x Se 1-x

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

[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 application, a method for preparing the above-mentioned photodetector with adjustable bias 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 by using an inductively coupled plasma etching technique;

[0014] (4) depositing a p-type narrow-bandgap semiconductor layer on the surface of the p-type wide-bandgap semiconductor layer by using a low-temperature thermal evaporation technique, with the low-temperature thermal evaporation temperature being controlled to be 350-400°C;

[0015] (5) depositing a first metal electrode on the surface of the p-type wide-bandgap semiconductor layer and a second metal electrode on the surface of the p-type narrow-bandgap semiconductor layer by using an electron beam evaporation technique.

[0016] Preferably, the buffer layer is epitaxially grown on a substrate, and the p-type wide-bandgap semiconductor layer is epitaxially grown on the buffer layer by using a metal organic chemical vapor deposition technique, a molecular beam epitaxy technique or a hydride vapor phase epitaxy technique.

[0017] According to another aspect of the present application, a method for using the above-mentioned photodetector for photodetection is provided, and the photodetector can achieve:

[0018] i) detection of ultraviolet light;

[0019] and / or ii) detection of ultraviolet and infrared wide spectrum;

[0020] wherein the specific steps for detecting ultraviolet light are as follows: determining the wavelength of a radiation light source, and when the wavelength of the radiation light source is 200-365 nm, irradiating the light source on the photodetector, at this time, the energy of the photons is greater than the bandgap width of the p-type wide-bandgap semiconductor layer, and no bias or a positive bias is applied to the photodetector, and the photo-generated carriers are separated to form a photocurrent under the action of the built-in electric field or the applied positive bias, so as to realize the detection of the intensity of the ultraviolet light.

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

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

[0023] Overall, compared with the prior art, the above technical scheme conceived by the present application mainly has the following technical advantages:

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

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

[0026] (3) The present application is based on the semiconductor heterostructure integrated by van der Waals heterojunction, utilizes the low-temperature thermal evaporation technology, controls the low-temperature thermal evaporation temperature to be 350-400℃, and high-quality integrates the p-type wide band gap semiconductor and the p-type narrow band gap semiconductor, thereby avoiding the strict conditions of traditional heteroepitaxial growth lattice matching, 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 voltage adjustable photodetector of the present application based on the photovoltaic effect works under the action of the built-in electric field without applying a bias voltage or applying a very small bias voltage, and has the characteristics of low dark current and low power consumption. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The bias-adjustable photodetector structure of embodiment 1 of the present application.

[0029] Figure 2 The working schematic diagram of the bias-adjustable photodetector of embodiment 2 of the present application.

[0030] Figure 3 The working band diagram of the bias-adjustable photodetector of the present application under different bias, a positive bias, b negative bias.

[0031] Figure 4 The normalized spectral response curve of the detector under -2 and +2V bias respectively in embodiment 2.

[0032] Figure 5 The responsivity curve of the detector under -2V bias with the change of incident light wavelength in embodiment 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 scheme and advantages of the present application more clear and understandable, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0035] The present application 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 application introduces semiconductor heterojunction and photovoltaic effect into the detection structure. The detector structure is based on semiconductor heterojunction. The built-in electric field or external bias of the semiconductor heterojunction interface is used to drive the transport of photo-generated carriers to complete the conversion of optical signal to electrical signal at room temperature, which can realize high-sensitivity, low-power ultraviolet-infrared wide spectrum photodetection of the detector.

[0036] Embodiment 1

[0037] The present application proposes a preparation method of a bias-adjustable photodetector, which specifically includes the following steps:

[0038] (1) Selection of substrate 1: 2-inch sapphire is selected as substrate 1, and the thickness is 430 microns.

[0039] (2) Growth of buffer layer 2: An aluminum nitride (AlN) buffer layer 2 with a thickness of 1 micrometer was grown on the sapphire substrate 1 by 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, in which the flow rate of NH3 was constant at 62461 pmol / min, and the flow rate of TMAl was 13 pmol / min, so as to maintain the molar ratio of V group elements to III group elements introduced into the reaction chamber to be 4811.

[0040] (3) Growth of p-type wide-bandgap semiconductor layer 3: A gallium nitride (GaN) film with a thickness of 700 nanometers was grown on the AlN buffer layer 2 by MOCVD technology, and Mg doping was performed thereon, in which trimethylgallium (TMGa), ammonia (NH3) and dimethyl magnesium (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, in which the flow rate of NH3 was constant at 62461 pmol / min, and the flow rate of TMGa was 30 pmol / min, so as to maintain the molar ratio of V group elements to III group elements introduced into the reaction chamber to be 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 by using a maskless lithography technology, and then the GaN film was etched into a periodic array structure by using an inductively coupled plasma etching technology (ICP), in which chlorine gas / boron trichloride (Cl2 / BCl3) mixed gas was used as etching gas, the temperature of the reaction chamber was set to 20°C, the flow rate of Cl2 was constant at 10 sccm, the flow rate of BCl3 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: A tellurium selenium alloy (Te x Se 1-x ) film with a thickness of 300 nanometers was deposited on the etched P-type GaN film by combining maskless lithography and low-temperature thermal evaporation technology, in which Se powder and Te powder were used as Se source and Te source, respectively, the evaporation chamber had a vacuum degree of 1.5 x 10 -4 Pa, the evaporation rates of the Se source and the Te source were and respectively, and the mass ratio of the Se source to the Te source was about 0.66:1. Then, a heat annealing treatment at 240°C was performed in a nitrogen atmosphere to improve the crystal quality of the film, so as to deposit a Te x Se 1-x film on the P-type GaN film.

[0043] (6) The preparation of the first metal electrode 5: the electrode pattern with specific pattern structure is obtained by a maskless lithography technique, then a nickel metal layer and a gold metal layer are respectively deposited by an electron beam evaporation technique, the thicknesses of the nickel metal layer and the gold metal layer are 20 nm and 30 nm respectively, finally, rapid thermal annealing treatment is carried out in an air atmosphere to form a good ohmic contact, the annealing temperature is 700 DEG C, and the annealing time is 10 min, so that the prepared nickel-gold alloy electrode is used as the electrode of the p-type GaN thin film.

[0044] The preparation of the second metal electrode 6: the electrode pattern with specific pattern structure is obtained by a maskless lithography technique, then a gold metal layer is deposited by an electron beam evaporation technique, the thickness of the gold metal layer is 50 nm, so that the prepared gold electrode is used as the electrode of the Te x Se 1-x thin film.

[0045] Example 2

[0046] The application provides a method for ultraviolet-infrared wide-spectrum photoelectric detection by using a bias-adjustable photoelectric detector, and specifically comprises the following steps:

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

[0048] (2) setting the output voltage of the semiconductor parameter analyzer to -2 V, simultaneously scanning the wavelength of the irradiated light of the adjustable monochromatic light source, the scanning range is 200-1800 nm, the scanning step is 20 nm, and the photoelectric current value generated by the detector at each wavelength is recorded;

[0049] (3) setting the output voltage of the semiconductor parameter analyzer to +2 V, simultaneously scanning the wavelength of the irradiated light of the adjustable monochromatic light source, the scanning range is 200-360 nm, the scanning step is 20 nm, and the photoelectric current value generated by the detector at each wavelength is recorded.

[0050] Figure 2 is a working schematic diagram of Example 2, when the photons with specific energy irradiate on the device, the photo-generated electron-hole pairs are generated in the semiconductor heterojunction region, and are separated under the driving of the or external bias, to form a photo-generated current, at this time, the obvious jump of the current can be observed by detecting the current between the two electrodes;

[0051] Figure 3 is a working principle diagram of the application, under the positive bias or zero bias, Figure 3 in a), the photo-generated carriers excited by ultraviolet light in the GaN can be collected by an external circuit to form a photoelectric current. However, the Te x Se 1-xPhotogenerated holes in the detector are blocked by the valence band barrier and eventually recombine with electrons from the external circuit, failing to be collected to form a photocurrent. Therefore, under these conditions, the detector cannot respond to Te. x Se 1-x The absorbed radiation is only a response to ultraviolet radiation absorbed by GaN, and its spectral response range only includes the ultraviolet region. However, under negative bias ( Figure 3 In part b), the transport direction of photogenerated carriers is reversed, and Te x Se 1-x Photogenerated carriers generated in GaN can be successfully collected without the obstruction of potential barriers, thus achieving a broadband response in the ultraviolet-infrared spectrum.

[0052] Figure 4 The graphs show the normalized spectral response curves of the detector in Example 2 under bias voltages of -2V and +2V. As can be seen from the graphs, when the bias voltage is -2V, the device exhibits two response peaks near 360nm and 1060nm, which is a broadband ultraviolet-infrared detection mode. When the bias voltage is +2V, the device's light response quickly cuts off near 360nm, which is a broadband ultraviolet detection mode.

[0053] Example 3

[0054] This invention proposes a method for using a bias-tunable photodetector for ultraviolet-infrared broadband photodetection, specifically including the following steps:

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

[0056] Figure 5 The curve showing the responsivity of the detector in Example 3 under a -2V bias voltage as a function of incident light wavelength reveals response peaks at 365nm and 1060nm, with values ​​of 0.96 A / W and 0.58 A / W, respectively. This demonstrates excellent ultraviolet-infrared broadband detection performance. The results indicate that the bias-tunable photodetector of this invention can achieve broadband detection from ultraviolet to infrared, and its detection wavelength range can be controlled by the bias voltage, thereby improving the practicality of semiconductor material photonic detection devices.

[0057] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A bias-adjustable photodetector, characterized in that, The detector, from bottom to top, consists of: a substrate (1), a buffer layer (2), a p-type wide bandgap semiconductor layer (3), and a p-type narrow bandgap semiconductor layer (4). The p-type narrow bandgap semiconductor layer (4) partially covers the p-type wide bandgap semiconductor layer (3). The detector also includes a first metal electrode (5) and a second metal electrode (6). The first metal electrode (5) is disposed on the p-type wide bandgap semiconductor layer (3), and the second metal electrode (6) is disposed on the p-type narrow bandgap semiconductor layer (4). The first metal electrode (5) does not contact the p-type narrow bandgap semiconductor layer (4). The bandgap width of the p-type wide bandgap semiconductor layer (3) is 3.1~5 eV, and the bandgap width of the p-type narrow bandgap semiconductor layer (4) is 0.3~1.2 eV. 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. 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 of x in the equation ranges from 0.2 to 0.

8.

2. The bias-adjustable photodetector according to claim 1, characterized in that, The buffer layer (2) is made of AlN and has 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.

3. A bias-adjustable photodetector according to claim 2, 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.

4. A method for fabricating a bias-adjustable photodetector as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Epitaxially grow a buffer layer on the substrate; (2) An epitaxial growth of a p-type wide bandgap semiconductor layer on the buffer layer; (3) The p-type wide bandgap semiconductor layer is etched using inductively coupled plasma etching technology; (4) Using low-temperature thermal evaporation technology, the low-temperature thermal evaporation temperature is controlled at 350~400℃ to deposit a p-type narrow bandgap semiconductor layer on the surface of the p-type wide bandgap semiconductor layer; (5) A first metal electrode is deposited on the surface of a p-type wide bandgap semiconductor layer using electron beam evaporation technology, and a second metal electrode is deposited on the surface of a p-type narrow bandgap semiconductor layer.

5. A method for fabricating a bias-adjustable photodetector as described in claim 4, wherein the techniques used for epitaxially growing a buffer layer on the substrate and epitaxially growing a p-type wide bandgap semiconductor layer on the buffer layer are all selected from one of chemical vapor deposition, molecular beam epitaxy, and hydride vapor phase epitaxy.

6. A method for photoelectric detection using the detector as described in any one of claims 1-3, characterized in that, The detector is capable of: i) Detection of ultraviolet light; and / or ii) detection of the ultraviolet and infrared broad spectrum; The specific steps for detecting ultraviolet light are as follows: the wavelength of the radiation source is measured. When the wavelength of the radiation source is 200~365 nm, the source is irradiated onto the detector. At this time, the energy of the photon is greater than the band gap of the p-type wide band gap semiconductor layer. No bias voltage is applied to the detector or a positive bias voltage is applied to the detector. The generated photogenerated carriers are separated into photocurrents under the action of the built-in electric field or the external positive bias voltage, so as to realize the detection of ultraviolet light intensity. The specific steps for detecting the ultraviolet and infrared broadband spectrum are as follows: Measure the wavelength of the radiation source. When the wavelength of the radiation source is 200~1800nm, irradiate the detector with the source. At this time, the energy of the photon is greater than the bandgap of the p-type narrow bandgap semiconductor layer and less than the bandgap of the p-type wide bandgap semiconductor layer. Apply a negative bias voltage to the detector. Under the action of the negative bias voltage, photogenerated electrons and holes separate to form a photocurrent, thereby realizing the detection of the intensity of the ultraviolet and infrared broadband spectrum.

7. A method for photoelectric detection using the detector as described in claim 6, characterized in that, The positive bias voltage is below 5V; the negative bias voltage is -5 to -1V.

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