CN110364582B - AlGaN nano-pillar MSM-type ultraviolet detector based on graphene template and preparation method thereof - Google Patents

Abstract

The invention discloses an AlGaN nano-pillar based MSM ultraviolet detector based on a graphene template and a preparation method thereof. The ultraviolet detector comprises a substrate, a graphene template layer, an AlGaN nano column, a Ni first metal layer and an Au second metal layer, wherein the substrate, the graphene template layer, the AlGaN nano column and the Au second metal layer form Schottky contact with each other, the Si ₃N₄ insulating layer is filled in the AlGaN nano column, and the Ni first metal layer and the Au second metal layer are used as electrode materials to form interdigital electrodes. The forbidden bandwidth of the AlGaN material can be continuously adjusted from 3.4 eV to 6.2 eV according to the difference of Al components, so that light with the wavelength of 200 nm to 365 nm can be effectively detected, and the AlGaN material has good solar blind property; the ultraviolet detector has very high sensitivity detection on UVA-C ultraviolet light, and can be applied to the fields of ultraviolet missile guidance, open fire detection, solar illuminance detection and the like.

Description

An MSM-type ultraviolet detector based on AlGaN nanocolumn on graphene template and its preparation method

Technical Field

The invention relates to the technical field of ultraviolet detectors, and in particular to an AlGaN nano-column-based MSM type ultraviolet detector on a graphene template and a preparation method thereof.

Background Art

Ultraviolet detection technology is widely used in military and civilian applications due to its advantages such as good day-blind characteristics, non-line-of-sight communication, low eavesdropping rate and no background signal interference. In the military, it is mainly used in ultraviolet communication, missile guidance, missile warning, ultraviolet analysis and biochemical analysis. In civilian applications, it is mainly used in environmental testing, biomedical analysis, ozone detection, open fire detection and solar illumination detection. At present, Si-based photodiode ultraviolet detectors are widely used in industrialization, but because the detection area of Si includes visible light, ultraviolet light detection can only be achieved after installing a filter system, which increases the volume and cost. In addition, Si has a strong ability to absorb ultraviolet light and weak radiation resistance, which limits the development of ultraviolet detectors.

The third generation of wide bandgap semiconductor materials (including GaN, AlN, InN, and ternary and quaternary compounds) are very suitable for the production of high-frequency, high-power, high-integration and radiation-resistant electronic devices due to their wide bandgap, fast electron migration rate, good thermal stability and strong radiation resistance. They are widely used in many fields such as light-emitting diodes, ultraviolet detection devices and solar cells. AlGaN materials have wide bandgap and direct bandgap. By adjusting the composition of the alloy, the bandgap can be continuously adjusted from 3.4 eV to 6.2 eV, which is equivalent to a cutoff wavelength of 200 nm to 365 nm. It has visible light blindness and solar blindness characteristics. This feature enables it to detect ultraviolet signals under the interference of visible light and sunlight, without the need for a filter system or shallow junction, and is an ideal material for preparing ultraviolet detectors. Although AlGaN-based ultraviolet detectors have made certain breakthroughs, they are still far from commercial applications. The main factors restricting the development of AlGaN-based ultraviolet detectors are: the heteroepitaxial GaN/AlGaN film has high dislocation density, large warping and easy cracking, which makes device preparation difficult. The one-dimensional AlGaN nanostructure phase can well overcome the shortcomings of traditional AlGaN films. Specifically: (1) The crystal quality of heteroepitaxial one-dimensional AlGaN nanomaterials is better than that of thin films, because the one-dimensional nanostructure has a large specific surface area, which can effectively reduce the dislocations penetrating to the top of the nanorods, help reduce defects and improve crystal quality; (2) The one-dimensional AlGaN nanostructure greatly increases the sidewall area of the material, thereby increasing the photon escape/absorption angle and effectively improving light emission/absorption.

CVD is a common method for synthesizing one-dimensional AlGaN nanomaterials. Compared with MOCVD, MBE, PLD, HVPE and other methods, the MBE method has a very low growth rate, the PLD method is difficult to grow in large sizes, and the HVPE method has low control accuracy. The CVD method has the advantages of high growth rate, low cost, simple operation, etc., and is suitable for large-scale industrialization. However, the one-dimensional nanomaterials prepared by the CVD method are currently based on catalyst-assisted VLS growth method or template selective growth method. Among them, 1) the catalyst-assisted VLS growth method requires the use of metal nanoparticles as catalysts. During the growth process, the nanocolumns often have different orientations and tend to twist, tilt and branch; 2) the template selective growth method usually requires a series of extremely complex and expensive technologies, such as electron beam exposure and focused ion beam milling, to prepare an orderly arranged and upright nanocolumn array, resulting in high cost and low efficiency. How to efficiently and low-cost prepare a one-dimensional AlGaN nanocolumn array with good orientation and uniform arrangement is a current problem.

Summary of the invention

The purpose of the present invention is to address the deficiencies of the prior art and provide an MSM-type ultraviolet detector based on AlGaN nano-column on a graphene template and a preparation method thereof. The ultraviolet detector has the characteristics of low dark current and high light response.

The present invention also aims to provide a method for preparing the MSM type ultraviolet detector based on AlGaN nano-column on graphene template. The preparation method has simple process, low energy consumption, time saving and high efficiency.

The purpose of the present invention is achieved by at least one of the following technical solutions.

An MSM type ultraviolet detector based on AlGaN nanocolumns on a graphene template includes, from bottom to top, a substrate, a graphene template layer, an AlGaN nanocolumn, a Ni first metal layer and an Au second metal layer forming Schottky contact with the AlGaN nanocolumns, and also includes _{a Si3N4 insulating} layer filled with the AlGaN nanocolumns, and the Ni first metal layer and the Au second metal layer are used as electrode materials to form interdigital electrodes.

Furthermore, the thickness of the substrate is 420-430 μm.

Furthermore, the substrate is a sapphire, Si or La _0.3 Sr _1.7 AlTaO ₆ substrate.

Furthermore, the number of layers of the graphene template layer is 1 to 3, and the thickness is 3 to 5 nm.

Furthermore, the AlGaN nanocolumn has a length of 300-500 nm and a diameter of 100-200 nm.

Furthermore, the thickness of the Ni first metal layer and the Au second metal layer are 40-50 nm and 100-150 nm respectively.

Furthermore, the length of the interdigital electrodes is 280-340 μm, the width is 10-15 μm, the electrode spacing is 10-15 μm, and the number of pairs is 12-20.

The method for preparing the MSM type ultraviolet detector based on AlGaN nano-column on graphene template comprises the following steps:

(1) After cleaning the substrate to remove residual contaminants and oxides on the surface, a graphene layer is grown on the substrate surface to form a substrate/graphene structure. Since there are defect holes on the surface of the graphene layer, it can be used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

(2) growing AlGaN nanocolumns on the substrate/graphene structure to form a substrate/graphene/AlGaN nanocolumn structure;

(3) growing a Si ₃ N ₄ insulating layer on the substrate/graphene/AlGaN nanocolumn structure to fill the gaps between the AlGaN nanocolumns, thereby forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure;

(4) cleaning the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure, and then performing photolithography, using an electron beam evaporation coating system to sequentially evaporate two metal layers of Ni and Au as electrodes on the surface of the insulating layer structure, removing the resist, and obtaining a Ni/Au metal interdigital electrode in Schottky contact with the AlGaN nanocolumn layer, thereby forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure, and performing thermal annealing;

(5) Plating the substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure to form solder joints, thinning, dicing, wire bonding, and then packaging to obtain the ultraviolet detector.

Furthermore, in step (1), the cleaning is: using 6-10wt% HF aqueous solution for ultrasonic cleaning for 8-10 min to remove residual impurities on the surface, then using acetone and anhydrous ethanol for ultrasonic cleaning for 8-10 min and 3-5 min respectively to remove organic impurities on the surface, then using deionized water for ultrasonic cleaning for 3-5 min, and finally using a nitrogen gun to blow away water vapor on the surface.

Furthermore, in step (1), PECVD is used to grow a graphene layer, and the process conditions are as follows: a mechanical pump and a molecular pump are used to evacuate the quartz tube until the pressure is maintained at 1~2× ^10-4 Pa, the substrate is heated to 950~1000°C, the molecular pump is stopped and _H2 and _CH4 are introduced into the cavity, with flow rates of 80~150 sccm and 20~30 sccm respectively, and the pressure is maintained at 30~100 Pa. During the deposition process, the RF plasma power is maintained at 200~300 W. After the deposition is completed, the substrate is cooled to room temperature in an Ar gas atmosphere. There are defect holes on the surface of the deposited graphene layer, so it serves as a template layer for the self-growth of AlGaN nanocolumns in the next step.

Furthermore, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are as follows: using a mechanical pump and a molecular pump to evacuate the quartz tube until the pressure is maintained at 1~2× ^10-4 Pa, heating the substrate/graphene structure to 850~950°C, using Al powder and Ga balls as Al source and Ga source of AlGaN material, heating the Al powder to 1000~1100°C; heating the Ga balls to 850~950°C; then stopping the molecular pump and then introducing _N2 and _H2 into the cavity as carrier gases, with flow rates of 60~100 sccm and 20~30 sccm respectively, introducing _NH3 as a reaction gas, with a flow rate of 20~30 sccm, maintaining the RF plasma power at 150~250 W during the growth process, maintaining the pressure in the reaction chamber at 50~100 Pa, and depositing to form AlGaN nanocolumns, and after the deposition is completed, cooling the substrate to room temperature in a _N2 atmosphere.

Furthermore, by controlling the different heating evaporation temperatures in the source region, the molar fraction of the Al component of AlGaN can be adjusted from 0 to 1, realizing Al _x Ga _(1-x) N (0<x<1), and the band gap can be continuously adjusted from 3.4 eV to 6.2 eV.

Furthermore, in step (3), a Si ₃ N ₄ insulating filling layer is grown by PECVD, and the process conditions are as follows: a mechanical pump and a molecular pump are used to evacuate the quartz tube until the pressure is maintained at 1~2×10 ^-4 Pa, the substrate/graphene/AlGaN nanorod structure is heated to 450~550 ℃, and then the molecular pump is stopped and SiH ₄ and NH ₃ are introduced into the cavity, with flow rates of 20~30 sccm and 100~150 sccm, respectively. During the growth process, the RF plasma power is maintained at 250~300 W, and the pressure in the reaction chamber is maintained at 40~90 Pa to deposit the Si ₃ N ₄ insulating filling layer.

Furthermore, in step (4), the cleaning treatment is: first ultrasonic cleaning with acetone and alcohol for 8-10 min and 3-5 min respectively to remove organic impurities on the surface, then ultrasonic cleaning with deionized water for 3-5 min to remove inorganic impurities on the surface, and finally blowing away water vapor on the surface with a nitrogen gun.

Furthermore, in step (4), the photolithography process is as follows: firstly, coating the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, then using a coater to spin coat the negative photoresist for 40 to 60 seconds, and then pre-baking, exposing, post-baking, developing, hardening, and using _O2 plasma for reactive ion etching for 2 to 4 minutes, cleaning, and finally drying with hot nitrogen for 5 to 10 minutes.

Furthermore, the pre-baking is performed in an oven at 65-75° C. for 5-8 min.

Furthermore, the exposure is to place the sample after pre-baking and the photolithography mask on the photolithography machine at the same time, and then irradiate with ultraviolet light for 5 to 7 seconds.

Furthermore, the post-baking is performed in an oven at 85-95° C. for 2-3 min.

Furthermore, the development is to dissolve the post-baking sample in a 6-8 wt% tetrabutylammonium hydroxide aqueous solution developer for 60-100 s.

Furthermore, the hardened film is heated in an oven at 55-75° C. for 6-8 min.

Furthermore, the cleaning is to use deionized water ultrasonic cleaning for 3 to 5 minutes to remove inorganic impurities on the surface, and finally use a nitrogen gun to blow away the water vapor on the surface.

Furthermore, in step (4), the electron beam evaporation electrode plating process is as follows: the cleaned and dried insulating layer structure is placed in an electron beam evaporation coating system, and after the mechanical pump and molecular pump are evacuated to 5.0~6.0× ^10-4 Pa, the metal electrode is started to be evaporated, the metal evaporation rate is controlled to 2.0~3.0 Å/s, and the sample disk rotation speed is 10~20 r/min.

Furthermore, in step (4), the degumming is performed by soaking in acetone for 20 to 25 minutes and then ultrasonically treating for 1 to 3 minutes, thereby removing unnecessary parts and leaving the desired interdigital electrode pattern.

Since the graphene surface of the complete lattice is saturated with dangling bonds that are not easily adsorbed, and there are dangling bonds in the defects (nanoscale) on the natural graphene surface, this provides a natural nano-void template for growing one-dimensional AlGaN nanocolumn arrays, so two-dimensional graphene is used as the seed layer template for the epitaxial growth of this one-dimensional nanoarray structure; at the same time, graphene has excellent conductivity and improves the carrier transport of optoelectronic devices. In addition, compared with other types of ultraviolet detectors such as PIN type and avalanche type ultraviolet detectors, MSM type ultraviolet detectors have been more and more widely used due to their many advantages such as simple structure, fast response speed, and high light response.

Compared with the prior art, it has the following advantages and beneficial effects:

(1) The present invention utilizes the nucleation points of the graphene template layer to directly grow AlGaN nanorods on the graphene/substrate by CVD van der Waals epitaxy, overcoming the shortcomings of the catalyst-assisted VLS growth method and the template selective growth method, and has the characteristics of simple process, time-saving, high efficiency and low energy consumption, which is conducive to large-scale production;

(2) The AlGaN nanocolumn-based MSM ultraviolet detector based on the graphene template of the present invention uses AlGaN nanocolumn material as the active layer material. Since the band gap of the AlGaN material can be continuously adjusted from 3.4 eV to 6.2 eV according to the different Al components, it can effectively detect light with a wavelength of 200 nm to 365 nm and has good solar-blind characteristics.

(3) The MSM-type ultraviolet detector based on AlGaN nanocolumns on a graphene template of the present invention utilizes the huge specific surface area and quantum confinement of the one-dimensional nanocolumn material to increase the density and transmission time of photogenerated carriers, thereby obtaining a highly sensitive and ultrafast light response;

(4) The MSM-type ultraviolet detector based on AlGaN nanocolumns on a graphene template of the present invention can achieve high-sensitivity detection of UVA-C ultraviolet light, and can be applied to the fields of ultraviolet missile guidance, open fire detection, and solar illumination detection, with considerable economic benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic cross-sectional view of the structure of an ultraviolet detector of the present invention;

FIG2 is a schematic top view of the electrode structure of the ultraviolet detector of the present invention;

3 is a curve showing the change of current with applied bias voltage of the MSM-type ultraviolet detector based on Al _0.02 Ga _0.98 N nano-column on graphene template with Al component of 0.02 prepared in Example 1;

FIG4 is a curve showing the change of current with applied bias voltage of the Al _0.3 Ga _0.7 N nano-column-based MSM type ultraviolet detector based on a graphene template with an Al component of 0.3 prepared in Example 2;

FIG5 is a curve showing the variation of the current of the MSM-type ultraviolet detector based on Al _0.98 Ga _0.02 N nano-column on the graphene template with an Al component of 0.98 prepared in Example 3 as a function of the applied bias voltage.

DETAILED DESCRIPTION

The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings, but the implementation manner and protection scope of the present invention are not limited thereto.

In a specific embodiment, the structural cross-sectional schematic diagram of the MSM-type ultraviolet detector based on AlGaN nanocolumns on a graphene template of the present invention is shown in Figure 1, which includes, from bottom to top, a substrate 1, a graphene template layer 2, an AlGaN nanocolumn 3, a Ni first metal layer 5 and an Au second metal layer 6 forming a Schottky contact with the AlGaN nanocolumns, and also includes _{a Si3N4} insulating layer 4 filled with AlGaN nanocolumns. The Ni first metal layer 5 and the Au second metal layer 6 are used as electrode materials to form interdigitated electrodes.

Among them, the thickness of the substrate 1 is 420~430 μm; the number of layers of the graphene template layer 2 is 1~3, and the thickness is 3~5 nm; the length of the AlGaN nanocolumn 3 is 300~500 nm, and the diameter is 100~200 nm; the Ni first metal layer and the Au second metal layer interdigital electrodes are metal layer interdigital electrodes in which Ni and Au are stacked in sequence from bottom to top, among which the thicknesses of the Ni first metal layer 5 and the Au second metal layer 6 are 40~50 nm and 100~150 nm respectively, the length of the metal interdigital electrodes is 280~340 μm, the width is 10~15 μm, the electrode spacing is 10~15 μm, and the number of pairs is 12~20 pairs.

Example 1

A preparation method of an AlGaN nano-column-based MSM ultraviolet detector with an Al component content of 0.02 on a graphene template (the nano-columns are Al _0.02 Ga _0.98 N), specifically comprising the following steps:

(1) After cleaning the Si(111) substrate to remove residual contaminants and oxides on the surface, the substrate is placed in a plasma enhanced chemical vapor deposition device to grow a graphene layer on the substrate surface to form a substrate/graphene structure. Since there are defect holes on the surface of the graphene layer, it can be used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

(2) directly growing AlGaN nanorods on the substrate/graphene structure using the PECVD method to form a substrate/graphene/AlGaN nanorod structure;

(3) directly growing a Si ₃ N ₄ insulating layer on the substrate/graphene/AlGaN nanocolumn structure by PECVD to fill the gaps between the AlGaN nanocolumns, thereby forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure;

(4) The substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure is cleaned and then subjected to photolithography. Two metal layers of Ni and Au are sequentially deposited on the sample surface as electrodes using an electron beam evaporation coating system. After debonding, a Ni/Au metal interdigital electrode in Schottky contact with the AlGaN layer is obtained to form a substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure, which is then transferred to an annealing furnace for thermal annealing.

(5) Plating the substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure to form solder joints, thinning, dicing, wire bonding, and then packaging to obtain the ultraviolet detector.

Furthermore, in step (1), the cleaning is: ultrasonic cleaning with a 6 wt% HF aqueous solution for 10 min to remove residual impurities on the surface, then ultrasonic cleaning with acetone and anhydrous ethanol for 8 min and 5 min respectively to remove organic impurities on the surface, then ultrasonic cleaning with deionized water for 3 min, and finally blowing away water vapor on the surface with a nitrogen gun.

Furthermore, in step (1), the process conditions for growing the graphene layer by PECVD are as follows: using a mechanical pump and a molecular pump to evacuate the quartz tube until the pressure is maintained at 1.0×10 ^-4 Pa, heating the substrate to 950 °C, stopping the molecular pump and then introducing H ₂ and CH ₄ into the chamber at flow rates of 150 sccm and 30 sccm, respectively, maintaining the pressure at 100 Pa, maintaining the RF plasma power at 200 W during the deposition process, and cooling the substrate to room temperature in an Ar gas atmosphere after the deposition. There are defect holes on the surface of the deposited graphene layer, so it serves as a template layer for the self-growth of AlGaN nanocolumns in the next step;

Furthermore, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are as follows: vacuuming the quartz tube with a mechanical pump and a molecular pump until the pressure is maintained at 1×10 ^-4 Pa, heating the substrate/graphene structure to 950 °C, and using Al powder and Ga balls as Ga and Al sources of AlGaN materials. Then, the molecular pump is stopped and N ₂ and H ₂ are introduced into the chamber as carrier gases with flow rates of 60 sccm and 20 sccm, respectively, and NH ₃ is introduced as a reaction gas with a flow rate of 20 sccm. During the growth process, the RF plasma power is maintained at 250 W, and the pressure in the reaction chamber is maintained at 50 Pa to deposit and form AlGaN nanocolumns. After the deposition is completed, the substrate is cooled to room temperature in an N ₂ gas atmosphere.

Furthermore, the heating temperatures of the Al powder and Ga ball source regions are 1000° C. and 950° C., respectively, to achieve Al _0.02 Ga _0.98 N nanocolumns with an Al component of 0.02 and a bandgap of 3.46 eV.

Furthermore, in step (3), the PECVD growth process conditions of the Si ₃ N ₄ insulating filling layer are: using a mechanical pump and a molecular pump to evacuate the quartz tube to maintain a pressure of 1.0×10 ^-4 Pa, heating the substrate/graphene/AlGaN nanorod structure to 550 ° C, then stopping the molecular pump and then introducing SiH ₄ and NH ₃ into the cavity, with flow rates of 20 sccm and 100 sccm respectively, during the growth process, the RF plasma power is maintained at 250 W, and the pressure in the reaction chamber is maintained at 40 Pa to deposit the Si ₃ N ₄ insulating filling layer.

Furthermore, in step (4), the cleaning treatment is: first ultrasonically clean with acetone and alcohol for 10 minutes and 5 minutes respectively to remove organic impurities on the surface, then ultrasonically clean with deionized water for 3 minutes to remove inorganic impurities on the surface, and finally blow away the water vapor on the surface with a nitrogen gun.

Furthermore, in step (4), the photolithography process is as follows: firstly, coating the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, then using a coater to spin-coat the negative photoresist for 40 seconds, and then pre-baking, exposing, post-baking, developing, hardening, and using _O2 plasma for reactive ion etching for 4 minutes, cleaning, and finally drying with hot nitrogen for 5 minutes.

Furthermore, the pre-baking is performed by heating in an oven at 75° C. for 5 min.

Furthermore, the exposure is to place the sample after pre-baking and the photolithography mask on the photolithography machine at the same time, and then irradiate with ultraviolet light for 5 seconds.

Furthermore, the post-baking is performed by heating in an oven at 85° C. for 3 min.

Furthermore, the development is to dissolve the post-baking sample in a 6 wt % tetrabutylammonium hydroxide aqueous solution developer for 60 s.

Furthermore, the hardened film is heated in an oven at 75° C. for 6 min.

Furthermore, the cleaning is performed by ultrasonic cleaning with deionized water for 5 minutes to remove inorganic impurities on the surface, and finally the water vapor on the surface is blown away with a nitrogen gun.

Furthermore, in step (4), the electron beam evaporation electrode deposition process is as follows: the cleaned and dried sample is placed in the electronic book evaporation coating system, and after the mechanical pump and molecular pump are evacuated to 6.0× ^10-4 Pa, the metal electrode is deposited, and the metal evaporation rate is controlled to 2.0 Å/s, and the sample plate speed is 20 r/min.

Furthermore, in step (4), the degumming is performed by soaking in acetone for 20 minutes and then ultrasonically treating for 3 minutes, thereby removing unnecessary parts and leaving the desired interdigital electrode pattern.

The structural cross-sectional schematic diagram of the prepared Al component of 0.02 based on the AlGaN nanocolumn-based MSM type ultraviolet detector on the graphene template is shown in Figure 1, wherein the thickness of the Si (111) substrate 1 is 420 μm; the number of layers of the graphene template layer 2 is 1, and the thickness is 3 nm; the length of the AlGaN nanocolumn 3 is 500 nm and the diameter is 100 nm; the Ni first metal layer and the Au second metal layer interdigitated electrodes are metal layer interdigitated electrodes in which Ni and Au are stacked from bottom to top, wherein the thickness of the Ni first metal layer 5 and the Au second metal layer 6 are 50 nm and 150 nm respectively, the length of the metal interdigitated electrodes is 340 μm, the width is 15 μm, the electrode spacing is 10 μm, and the number of pairs is 14. The top view schematic diagram is shown in Figure 2.

The curve of the current of the AlGaN nanocolumn-based MSM type UV detector with an Al component of 0.02 on a graphene template as a function of the applied bias voltage is shown in Figure 3. The current increases with the increase of the applied bias voltage, and the image has good symmetry in the positive and negative pressure regions, indicating that a good Schottky contact has been formed. Under a bias of 1 V, the dark current is only 3.5 nA, indicating that the prepared photodetector has good dark current characteristics. Under 365 nm light irradiation, the current increases significantly (~μA), indicating that it has a very sensitive detection effect on UVA ultraviolet light.

Example 2

The preparation of an AlGaN nanocolumn-based MSM ultraviolet detector with an Al component of 0.3 on a graphene template (the nanocolumns are Al _0.3 Ga _0.7 N) specifically includes the following steps:

(1) After cleaning the sapphire substrate to remove residual contaminants and oxides on the surface, the sapphire substrate is placed in a plasma enhanced chemical vapor deposition (PECVD) device to grow a graphene layer on the substrate surface to form a substrate/graphene structure. Since there are defect holes on the surface of the graphene layer, it can be used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

(2) directly growing AlGaN nanorods on the substrate/graphene structure using the PECVD method to form a substrate/graphene/AlGaN nanorod structure;

(3) directly growing a Si ₃ N ₄ insulating layer on the substrate/graphene/AlGaN nanocolumn structure by PECVD to fill the gaps between the AlGaN nanocolumns, thereby forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure;

(4) The substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure is cleaned and then subjected to photolithography. Two metal layers of Ni and Au are sequentially deposited on the sample surface as electrodes using an electron beam evaporation coating system. After debonding, a Ni/Au metal interdigital electrode in Schottky contact with the AlGaN layer is obtained to form a substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure, which is then transferred to an annealing furnace for thermal annealing.

(5) Plating the substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure to form solder joints, thinning, dicing, wire bonding, and then packaging to obtain the ultraviolet detector.

Furthermore, in step (1), the cleaning is: using 8 wt% HF aqueous solution for ultrasonic cleaning for 9 minutes to remove residual impurities on the surface, then using acetone and anhydrous ethanol for ultrasonic cleaning for 10 minutes and 4 minutes respectively to remove organic impurities on the surface, then using deionized water for ultrasonic cleaning for 5 minutes, and finally using a nitrogen gun to blow away the water vapor on the surface.

Furthermore, in step (1), the process conditions for growing the graphene layer by PECVD are as follows: using a mechanical pump and a molecular pump to evacuate the quartz tube until the pressure is maintained at 2×10 ^-4 Pa, heating the substrate to 1000 °C, stopping the molecular pump and then introducing H ₂ and CH ₄ into the chamber at flow rates of 120 sccm and 25 sccm, respectively, maintaining the pressure at 70 Pa, maintaining the RF plasma power at 300 W during the deposition process, and cooling the substrate to room temperature in an Ar gas atmosphere after the deposition. There are defect holes on the surface of the deposited graphene layer, so it serves as a template layer for the self-growth of AlGaN nanocolumns in the next step;

Furthermore, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are as follows: vacuuming the quartz tube with a mechanical pump and a molecular pump until the pressure is maintained at 1.5×10 ^-4 Pa, heating the substrate/graphene structure to 900 °C, and using Al powder and Ga balls as Al sources and Ga sources of AlGaN materials. Then, the molecular pump is stopped and N ₂ and H ₂ are introduced into the cavity as carrier gases with flow rates of 80 sccm and 25 sccm, respectively, and NH ₃ is introduced as a reaction gas with a flow rate of 22 sccm. During the growth process, the RF plasma power is maintained at 150 W, and the pressure in the reaction chamber is maintained at 75 Pa to deposit and form AlGaN nanocolumns. After the deposition is completed, the substrate is cooled to room temperature in an N ₂ gas atmosphere.

Furthermore, the heating temperatures of the Al powder and Ga ball source regions are 1050°C and 930°C, respectively, achieving an Al component of 0.3 and a bandgap of about 4.20 eV in AlGaN.

Furthermore, in step (3), the PECVD growth process conditions of the Si ₃ N ₄ insulating filling layer are: using a mechanical pump and a molecular pump to evacuate the quartz tube to maintain a pressure of 2×10 ^-4 Pa, heating the substrate/graphene/AlGaN nanorod structure to 500 ° C, then stopping the molecular pump and then introducing SiH ₄ and NH ₃ into the cavity, with flow rates of 30 sccm and 150 sccm respectively, during the growth process, the RF plasma power is maintained at 280 W, and the pressure in the reaction chamber is maintained at 90 Pa to deposit the Si ₃ N ₄ insulating filling layer.

Furthermore, in step (4), the cleaning treatment is: first ultrasonically clean with acetone and alcohol for 8 minutes and 4 minutes respectively to remove organic impurities on the surface, then ultrasonically clean with deionized water for 5 minutes to remove inorganic impurities on the surface, and finally blow away the water vapor on the surface with a nitrogen gun.

Furthermore, in step (4), the photolithography process is as follows: firstly, coating the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, then using a coater to spin-coat the negative photoresist for 50 s, and then pre-baking, exposing, post-baking, developing, hardening, and using _O2 plasma for reactive ion etching for 3 min, cleaning, and finally drying with hot nitrogen for 10 min.

Furthermore, the pre-baking is performed by heating in an oven at 70° C. for 8 min.

Furthermore, the exposure is to place the sample after pre-baking and the photolithography mask on the photolithography machine at the same time, and then irradiate with ultraviolet light for 7 seconds.

Furthermore, the post-baking is performed in an oven at 95° C. for 2.5 min.

Furthermore, the development is to dissolve the post-baking sample in an 8 wt % tetrabutylammonium hydroxide aqueous solution developer for 80 s.

Furthermore, the hardened film is heated in an oven at 55° C. for 8 min.

Furthermore, the cleaning is performed by ultrasonic cleaning with deionized water for 3 minutes to remove inorganic impurities on the surface, and finally the water vapor on the surface is blown away with a nitrogen gun.

Furthermore, in step (4), the electron beam evaporation electrode deposition process is as follows: the cleaned and dried sample is placed in the electronic book evaporation coating system, and after the mechanical pump and molecular pump are evacuated to 5.5× ^10-4 Pa, the metal electrode is evaporated, and the metal evaporation rate is controlled to 3.0 Å/s, and the sample disk speed is 10 r/min.

Furthermore, in step (4), the degumming is performed by soaking in acetone for 25 minutes and then ultrasonically treating for 2 minutes, thereby removing unnecessary parts and leaving the desired interdigital electrode pattern.

The structural cross-sectional schematic diagram of the prepared Al component of 0.3 based on the AlGaN nanocolumn-based MSM type ultraviolet detector on the graphene template is shown in Figure 1, wherein the thickness of the Si (111) substrate 1 is 430 μm; the number of layers of the graphene template layer 2 is 3 and the thickness is 5 nm; the length of the AlGaN nanocolumn 3 is 300 nm and the diameter is 200 nm; the Ni first metal layer and the Au second metal layer interdigitated electrodes are metal layer interdigitated electrodes in which Ni and Au are stacked from bottom to top, wherein the thickness of the Ni first metal layer 5 and the Au second metal layer 6 are 40 nm and 100 nm respectively, the length of the metal interdigitated electrodes is 280 μm, the width is 10 μm, the electrode spacing is 15 μm, and the number of pairs is 12.

The curve of the current of the AlGaN nanocolumn-based MSM type UV detector with an Al component of 0.3 on the graphene template as a function of the applied bias voltage is shown in Figure 4. The current increases with the increase of the applied bias voltage, and the image has good symmetry in the positive and negative pressure regions, indicating that a good Schottky contact has been formed. Under a bias of 1 V, the dark current is only 8.8 nA, indicating that the prepared photodetector has good dark current characteristics. Under 295 nm light irradiation, the current increases significantly (~μA), indicating that it has a very sensitive detection effect on UVB ultraviolet light.

Example 3

The preparation of an MSM-type ultraviolet detector based on AlGaN nano-columns on a graphene template with an Al component of 0.98 (the nano-columns are Al _0.98 Ga _0.02 N) specifically includes the following steps:

(1) The La _0.3 Sr _1.7 AlTaO ₆ substrate is cleaned to remove residual contaminants and oxides on the surface, and then placed in a plasma enhanced chemical vapor deposition (PECVD) device to grow a graphene layer on the substrate surface to form a substrate/graphene structure. Since there are defect holes on the surface of the graphene layer, it can be used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

(2) directly growing AlGaN nanorods on the substrate/graphene structure using the PECVD method to form a substrate/graphene/AlGaN nanorod structure;

(3) directly growing a Si ₃ N ₄ insulating layer on the substrate/graphene/AlGaN nanocolumn structure by PECVD to fill the gaps between the AlGaN nanocolumns, thereby forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure;

(4) The substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure is cleaned and then subjected to photolithography. Two metal layers of Ni and Au are sequentially deposited on the sample surface as electrodes using an electron beam evaporation coating system. After debonding, a Ni/Au metal interdigital electrode in Schottky contact with the AlGaN layer is obtained to form a substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure, which is then transferred to an annealing furnace for thermal annealing.

(5) Plating the substrate/graphene/AlGaN nanorod/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigital electrode structure to form solder joints, thinning, dicing, wire bonding, and then packaging to obtain the ultraviolet detector.

Furthermore, in step (1), the cleaning is: ultrasonic cleaning with a 10 wt% HF aqueous solution for 8 min to remove residual impurities on the surface, then ultrasonic cleaning with acetone and anhydrous ethanol for 9 min and 3 min respectively to remove organic impurities on the surface, then ultrasonic cleaning with deionized water for 4 min, and finally blowing away water vapor on the surface with a nitrogen gun.

Furthermore, in step (1), the process conditions for growing the graphene layer by PECVD are as follows: using a mechanical pump and a molecular pump to evacuate the quartz tube until the pressure is maintained at 1.5×10 ^-4 Pa, heating the substrate to 980 °C, stopping the molecular pump and then introducing H ₂ and CH ₄ into the chamber at flow rates of 80 sccm and 20 sccm, respectively, maintaining the pressure at 30 Pa, maintaining the RF plasma power at 250 W during the deposition process, and cooling the substrate to room temperature in an Ar gas atmosphere after the deposition. There are defect holes on the surface of the deposited graphene layer, so it serves as a template layer for the self-growth of AlGaN nanocolumns in the next step;

Furthermore, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are as follows: vacuuming the quartz tube with a mechanical pump and a molecular pump until the pressure is maintained at 2×10 ^-4 Pa, heating the substrate/graphene structure to 850 °C, and using Al powder and Ga balls as Al sources and Ga sources for AlGaN materials. Then, the molecular pump is stopped and N ₂ and H ₂ are introduced into the chamber as carrier gases with flow rates of 100 sccm and 30 sccm, respectively, and NH ₃ is introduced as a reaction gas with a flow rate of 30 sccm. During the growth process, the RF plasma power is maintained at 200 W, and the pressure in the reaction chamber is maintained at 100 Pa to deposit and form AlGaN nanocolumns. After the deposition is completed, the substrate is cooled to room temperature in an N ₂ gas atmosphere.

Furthermore, the heating temperatures of the Al powder and Ga ball source regions are 1100° C. and 850° C., respectively, achieving an Al component of 0.98 in the AlGaN nanocolumns and an Al _0.98 Ga _0.02 N bandgap of 6.14 eV.

Furthermore, in step (3), the PECVD growth process conditions of the Si ₃ N ₄ insulating filling layer are as follows: using a mechanical pump and a molecular pump to evacuate the quartz tube to maintain a pressure of 1.5×10 ^-4 Pa, heating the substrate/graphene/AlGaN nanorod structure to 450 ° C, then stopping the molecular pump and then introducing SiH ₄ and NH ₃ into the cavity, with flow rates of 25 sccm and 130 sccm, respectively. During the growth process, the RF plasma power is maintained at 300 W, and the pressure in the reaction chamber is maintained at 80 Pa to deposit the Si ₃ N ₄ insulating filling layer.

Furthermore, in step (4), the cleaning treatment is: first ultrasonically clean with acetone and alcohol for 9 minutes and 3 minutes respectively to remove organic impurities on the surface, then ultrasonically clean with deionized water for 4 minutes to remove inorganic impurities on the surface, and finally blow away the water vapor on the surface with a nitrogen gun.

Furthermore, in step (4), the photolithography process is as follows: firstly, coating the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, then using a coater to spin coat the negative photoresist for 60 seconds, and then pre-baking, exposing, post-baking, developing, hardening, and using _O2 plasma for reactive ion etching for 2 minutes, cleaning, and finally drying with hot nitrogen for 8 minutes.

Furthermore, the pre-baking is performed by heating in an oven at 65° C. for 6 min.

Furthermore, the exposure is performed by placing the sample after pre-baking and the photolithography mask on a photolithography machine at the same time, and then irradiating with an ultraviolet light source for 6.5 seconds.

Furthermore, the post-baking is performed by heating in an oven at 90° C. for 2 min.

Furthermore, the development is to dissolve the post-baking sample in a 7 wt % tetrabutylammonium hydroxide aqueous solution developer for 100 s.

Furthermore, the hardened film is heated in an oven at 65° C. for 7 min.

Furthermore, the cleaning is performed by ultrasonic cleaning with deionized water for 4 minutes to remove inorganic impurities on the surface, and finally the water vapor on the surface is blown away with a nitrogen gun.

Furthermore, in step (4), the electron beam evaporation electrode deposition process is as follows: the cleaned and dried sample is placed in the electronic book evaporation coating system, and after the mechanical pump and molecular pump are evacuated to 5.0× ^10-4 Pa, the metal electrode is started to be evaporated, and the metal evaporation rate is controlled to 2.5 Å/s, and the sample plate speed is 12 r/min.

Furthermore, in step (4), the degumming is performed by soaking in acetone for 22 minutes and then ultrasonically treating for 1 minute, thereby removing unnecessary parts and leaving the desired interdigital electrode pattern.

The curve of the current of the AlGaN nanocolumn-based MSM type ultraviolet detector with an Al component of 0.98 on the graphene template as a function of the applied bias voltage is shown in Figure 5. The current increases with the increase of the applied bias voltage, and the image has good symmetry in the positive and negative pressure regions, indicating that a good Schottky contact has been formed. Under a bias of 1 V, the dark current is only 16.4nA, indicating that the prepared photodetector has good dark current characteristics. Under 200 nm light irradiation, the current increases significantly (~μA), indicating that it has a very sensitive detection effect on UVC ultraviolet light.

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims (9)

1. The preparation method of the AlGaN nanometer column base MSM type ultraviolet detector based on the graphene template is characterized by comprising the following steps:

After cleaning a substrate, growing a graphene template layer (2) on the surface of the substrate (1) to form a substrate/graphene structure;

Growing on the substrate/graphene structure in the step (one) to obtain an AlGaN nano column (3) to form a substrate/graphene/AlGaN nano column structure; the AlGaN nano-column is grown by PECVD, and the process conditions are as follows: vacuum pumping is carried out by using a mechanical pump and a molecular pump until the pressure in a quartz tube is maintained to be 1-2 multiplied by 10 ^-4 Pa, the substrate/graphene structure is heated to 850-950 ℃, al powder and Ga balls are adopted as an Al source and a Ga source of an AlGaN material, and the Al powder is heated to 1000-1100 ℃; heating the Ga balls to 850-950 ℃; then stopping a molecular pump, introducing N ₂ and H ₂ into the cavity as carrier gases, wherein the flow rates are respectively 60-100 sccm and 20-30 sccm, introducing NH ₃ as reaction gas, the flow rate is 20-30 sccm, maintaining the power of the radio frequency plasma at 150-250W in the growth process, maintaining the pressure in the reaction chamber at 50-100 Pa, depositing to form AlGaN nano columns, and cooling the substrate to room temperature under the atmosphere of N ₂ after the deposition is finished;

Thirdly, growing a Si ₃N₄ insulating layer (4) on the substrate/graphene/AlGaN nano-pillar structure in the second step to fill gaps among the AlGaN nano-pillars (3) so as to form a substrate/graphene/AlGaN nano-pillar/Si ₃N₄ insulating layer structure;

Fourthly, cleaning the substrate/graphene/AlGaN nano column/Si ₃N₄ insulating layer structure in the third step, performing photoetching treatment, sequentially evaporating two metal layers of Ni and Au on the surface of the insulating layer structure by using an electron beam evaporation coating system to serve as electrodes, removing photoresist to obtain a Ni/Au metal interdigital electrode which is in Schottky contact with the AlGaN nano column, forming a substrate/graphene/AlGaN nano column/Si ₃N₄ insulating layer structure/Ni/Au metal interdigital electrode structure, and performing thermal annealing treatment;

And fifthly, electroplating and welding spots, thinning, scribing and wire bonding are carried out on the substrate/graphene/AlGaN nano column/Si ₃N₄ insulating layer structure/Ni/Au metal interdigital electrode structure in the step (four), and then packaging is carried out, so that the MSM ultraviolet detector is obtained.

2. The method of claim 1, wherein in the step (one), the washing is: ultrasonically cleaning by using 6-10wt% of HF aqueous solution for 8-10 min, removing residual impurities on the surface, ultrasonically cleaning by using acetone for 8-10 min and then using absolute ethyl alcohol for 3-5 min in sequence, removing organic impurities on the surface, ultrasonically cleaning by using deionized water for 3-5 min, and finally blowing off water vapor on the surface by using a nitrogen gun.

3. The method of claim 1, wherein in step (one), the graphene layer is grown by PECVD, and the process conditions are: and vacuumizing by using a mechanical pump and a molecular pump until the pressure in the quartz tube is maintained to be 1-2 multiplied by 10 ^-4 Pa, heating the substrate to 950-1000 ℃, stopping the molecular pump, then introducing H ₂ and CH ₄,H₂ with the flow of 80-150 sccm and CH ₄ with the flow of 20-30 sccm into the cavity, maintaining the pressure to be 30-100 Pa, maintaining the power of the radio frequency plasma at 200-300W in the deposition process, and cooling the substrate to room temperature in Ar atmosphere after the deposition is finished.

4. The method according to claim 1, wherein in the step (iii), the Si ₃N₄ insulating filling layer is grown by PECVD, and the process conditions are as follows: and vacuumizing by using a mechanical pump and a molecular pump until the pressure in the quartz tube is maintained to be 1-2 multiplied by 10 ^{- 4} Pa, heating the substrate/graphene/AlGaN nano-pillar structure to 450-550 ℃, stopping the molecular pump, then introducing SiH ₄ and NH ₃,SiH₄ into the cavity at a flow rate of 20-30 sccm and NH ₃ at a flow rate of 100-150 sccm, maintaining the radio frequency plasma power at 250-300W in the growth process, and depositing a Si ₃N₄ insulating filling layer under the pressure maintained at 40-90 Pa in the reaction chamber.

5. The method according to claim 1, wherein in the step (four), the cleaning treatment is: firstly, sequentially carrying out ultrasonic cleaning for 8-10 min by using acetone and ultrasonic cleaning for 3-5 min by using alcohol to remove organic impurities on the surface, then carrying out ultrasonic cleaning for 3-5 min by using deionized water to remove inorganic impurities on the surface, and finally blowing off water vapor on the surface by using a nitrogen gun.

6. The method of claim 1, wherein in the step (iv), the photolithography process is: firstly coating an adhesion promoter HMDS, then spin-coating negative photoresist for 40-60 s by using a spin coater, performing pre-baking, exposure, post-baking, development and hardening, performing reactive ion etching treatment by adopting O ₂ plasma for 2-4 min, cleaning, and finally drying by using hot nitrogen for 5-10 min;

the pre-baking is to heat at 65-75 ℃ for 5-8 min in an oven;

The exposure is that a sample subjected to pre-baking treatment and a photoetching mask plate are simultaneously placed on a photoetching machine, and then an ultraviolet light source irradiates for 5-7 s;

the post-baking is to heat at 85-95 ℃ for 2-3 min in an oven;

The development is that a sample after post-baking treatment is put into a tetrabutylammonium hydroxide aqueous solution developer with the weight percent of 6-8% to be dissolved for 60-100 s;

The hardening is that heating treatment is carried out for 6-8 min at 55-75 ℃ in an oven;

And the cleaning is to ultrasonically clean the surface by using deionized water for 3-5 min, remove inorganic impurities on the surface, and finally blow off water vapor on the surface by using a nitrogen gun.

7. The method according to claim 1, wherein in the step (four), the electron beam evaporation electrode plating process is as follows: placing the cleaned and blow-dried insulating layer structure into an electron beam evaporation coating system, vacuumizing a mechanical pump and a molecular pump to 5.0-6.0X10 ^-4 Pa, starting to evaporate a metal electrode, controlling the metal evaporation rate to be 2.0-3.0A/s, and controlling the rotating speed of a sample disc to be 10-20 r/min; and photoresist removal is carried out by soaking in acetone for 20-25 min and then carrying out ultrasonic treatment for 1-3 min.

8. The AlGaN nano-pillar based MSM type ultraviolet detector on a graphene template prepared by the preparation method according to any one of claims 1 to 7, which is characterized by comprising a substrate (1), a graphene template layer (2), alGaN nano-pillars (3), a Ni first metal layer (5) and an Au second metal layer (6) which are in schottky contact with the AlGaN nano-pillars, and further comprising a Si ₃N₄ insulating layer (4) filled in the AlGaN nano-pillars, wherein the Ni first metal layer (5) and the Au second metal layer (6) are used as electrode materials to form an interdigital electrode.

9. The AlGaN nano-pillar based MSM type ultraviolet detector based on the graphene template according to claim 8, wherein the substrate (1) is a sapphire, si or La _0.3Sr_1.7AlTaO₆ substrate, and the thickness of the substrate (1) is 420-430 μm; the number of layers of the graphene template layer (2) is 1-3, and the thickness is 3-5 nm; the length of the AlGaN nano column (3) is 300-500 nm, and the diameter is 100-200 nm; the thickness of the Ni first metal layer (5) is 40-50 nm, and the thickness of the Au second metal layer (6) is 100-150 nm; the length of the interdigital electrode is 280-340 mu m, the width of the interdigital electrode is 10-15 mu m, the electrode spacing is 10-15 mu m, and the logarithm is 12-20 pairs.