CN110364582A - A kind of AlGaN nano-column-based MSM type ultraviolet detector based on graphene template and its preparation method - Google Patents

Abstract

The invention discloses an AlGaN nano column-based MSM type ultraviolet detector based on a graphene template and a preparation method thereof. The ultraviolet detector includes a bottom-up substrate, a graphene template layer, an AlGaN nanocolumn, a Ni first metal layer and an Au second metal layer forming a Schottky contact with the AlGaN nanocolumn, and also includes a filled AlGaN nanocolumn. The Si ₃ N ₄ insulating layer in the column, and the first metal layer of Ni and the second metal layer of Au are used as electrode materials to form interdigitated electrodes. The forbidden band width of the AlGaN material can be continuously adjusted from 3.4 eV to 6.2 eV according to the different Al components, so it can effectively detect light with a wavelength of 200 nm to 365 nm, and has good solar blindness characteristics; the ultraviolet light of the present invention The detector has a very high sensitivity to UVA-C ultraviolet light, and can be used in the fields of ultraviolet missile guidance, open flame detection and solar illuminance detection.

Description

A kind of MSM-type ultraviolet detector based on AlGaN nano-column base on graphene template and its Preparation

technical field

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

Background technique

Ultraviolet detection technology is widely used in military and civilian applications because of its good solar blindness, non-line-of-sight communication, low eavesdropping rate, and no background signal interference. In the military, it is mainly used in the fields of ultraviolet communication, missile guidance, missile early warning, ultraviolet analysis and biochemical analysis. In civilian use, it is mainly used in environmental detection, biomedical analysis, ozone detection, open flame detection and solar illumination detection, etc. At present, Si-based photodiode ultraviolet detectors are widely used in industrialization. However, since the detection area of Si includes visible light, the detection of ultraviolet light can only be realized after a filter system is installed, which increases the size and cost. In addition, Si has a strong ability to absorb ultraviolet light and weak anti-radiation ability, which limits the development of ultraviolet detectors.

The third-generation wide-bandgap semiconductor materials (including GaN, AlN, InN, and ternary and quaternary compounds) are very suitable because of their large band gap, fast electron mobility, good thermal stability, and strong radiation resistance. It is suitable for making electronic devices with high frequency, high power, high integration and radiation resistance, and is widely used in many fields such as light-emitting diodes, ultraviolet detection devices and solar cells. AlGaN material has a wide bandgap and a direct bandgap, which can be continuously adjusted from 3.4 eV to 6.2 eV by adjusting the composition of the alloy, which is equivalent to a cut-off wavelength of 200 nm to 365 nm, with visible light blindness and Solar-blindness, this feature enables it to detect ultraviolet signals even under the interference of visible light and sunlight, without the need for filter systems and shallow junctions, it is an ideal material for the preparation of ultraviolet detectors. Although AlGaN-based ultraviolet detectors have made some breakthroughs, they are far from commercial applications. The main factors restricting the development of AlGaN-based ultraviolet detectors are: heteroepitaxial GaN/AlGaN thin films with high dislocation density, large warpage and It is easy to crack, making device preparation difficult. The one-dimensional AlGaN nanostructure phase can well overcome the shortcomings of traditional AlGaN thin films. The specific performance is as follows: (1) The crystal quality of heteroepitaxial one-dimensional AlGaN nanomaterials is better than that of thin films, because the specific surface area of one-dimensional nanostructures is large, which can effectively reduce the dislocations penetrating to the top of nanorods, which contributes to 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 the synthesis of one-dimensional AlGaN nanomaterials. Compared with MOCVD, MBE, PLD, HVPE and other methods, the growth rate of MBE method is very low, PLD method is difficult to grow large size, and HVPE method has low control precision. CVD method has the advantages of high growth rate, low cost, and simple operation. It is suitable for large-scale industrialization. However, the one-dimensional nanomaterials prepared by the CVD method are all based on the catalyst-assisted VLS growth method or the template selective growth method. Among them, 1) the catalyst-assisted VLS growth method requires the use of metal nanoparticles as catalysts, and during the growth process, the nanopillars often have different orientations, tending to twist, tilt and branch; 2) the template selective growth method usually requires a series of extremely Complicated and expensive techniques, such as electron beam lithography and focused ion beam milling, etc., are required to fabricate ordered and vertically grown nanopillar arrays, resulting in high cost and low efficiency. How to prepare a one-dimensional AlGaN nanocolumn array with good orientation and uniform arrangement with high efficiency and low cost is a difficult problem at present.

Contents of the invention

The purpose of the present invention is to provide a kind of AlGaN nano-column-based MSM type ultraviolet detector based on graphene template and its preparation method for the deficiencies of the prior art. The ultraviolet detector has the characteristics of small dark current and high photoresponsivity.

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

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

A kind of AlGaN nanocolumn-based MSM ultraviolet detector based on a graphene template, including a bottom-up substrate, a graphene template layer, an AlGaN nanocolumn, and a Ni first metal layer forming a Schottky contact with the AlGaN nanocolumn and the Au second metal layer, and also include a Si ₃ N ₄ insulating layer filled with AlGaN nanocolumns, and the Ni first metal layer and the Au second metal layer are used as electrode materials to form an interdigitated electrode.

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

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

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

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

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

Further, the length of the interdigitated 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 preparation method of the above-mentioned AlGaN nano-column-based MSM type ultraviolet detector based on the graphene template comprises the following steps:

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

(2) AlGaN nanocolumns are grown 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 to form a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure;

(4) Clean the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure, and then perform photolithography treatment, and use the electron beam evaporation coating system to sequentially evaporate Ni on the surface of the insulating layer structure and Au two-layer metal layer as electrodes, remove glue, and obtain Ni/Au metal interdigitated electrodes in contact with AlGaN nano-column layer Schottky, forming substrate/graphene/AlGaN nano-column/Si ₃ N ₄ insulating layer structure/ Ni/Au metal interdigitated electrode structure, and thermal annealing treatment;

(5) The substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigitated electrode structure is electroplated, press-welded, thinned, diced and wire bonded, and then packaged. Obtain the UV detector.

Further, in step (1), the cleaning is: ultrasonic cleaning with 6-10wt% HF aqueous solution for 8-10 minutes to remove residual impurities on the surface, and then ultrasonic cleaning with acetone and absolute ethanol for 8-10 minutes respectively min and 3-5 min to remove organic impurities on the surface, then use deionized water to ultrasonically clean for 3-5 min, and finally use a nitrogen gun to blow off the water vapor on the surface.

Further, in step (1), PECVD is used to grow the graphene layer, and the process conditions are: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1~2×10 ^-4 Pa, and the substrate is heated to 950~ 1000 ℃, stop the molecular pump and then feed H ₂ and CH ₄ into the cavity, the flow rates are 80-150 sccm and 20-30 sccm respectively, the pressure is maintained at 30-100 Pa, and the RF plasma power is kept at 200 during the deposition process. ~300 W. After the deposition, the substrate was cooled to room temperature in an Ar gas atmosphere. There were defects and holes on the surface of the deposited graphene layer, so it was used as a template layer for the self-growth of AlGaN nanocolumns in the next step.

Further, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1~2×10 ^-4 Pa, and the substrate/graphene structure Heating to 850-950 °C, using Al powder and Ga balls as the Al source and Ga source of the AlGaN material, heating the Al powder to 1000-1100 °C; heating the Ga balls to 850-950 °C; then stopping the molecular pump and feeding N ₂ and H ₂ are fed into the chamber as carrier gas with flow rates of 60-100 sccm and 20-30 sccm respectively, and NH ₃ is fed as reaction gas with flow rate of 20-30 sccm. During the growth process, the RF plasma power is kept at 150-250 W, and the pressure in the reaction chamber was maintained at 50-100 Pa to deposit and form AlGaN nanocolumns. After the deposition, the substrate was cooled to room temperature under N ₂ gas atmosphere.

Furthermore, by controlling the different heating and evaporation temperatures of the source region, the mole fraction of the Al component of AlGaN can be adjusted from 0 to 1 to realize Al _x Ga _(1-x) N (0<x<1), the bandgap width Continuously adjustable from 3.4 eV to 6.2 eV.

Furthermore, in step (3), the Si ₃ N ₄ insulating filling layer is grown by PECVD, and the process conditions are: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1~2×10 ^-4 Pa, and the substrate/ The graphene/AlGaN nano-column structure is heated to 450-550 ℃, 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, radio frequency plasma The power is kept at 250-300 W, and the pressure in the reaction chamber is maintained at 40-90Pa to deposit the Si ₃ N ₄ insulating filling layer.

Further, in step (4), the cleaning process is as follows: first use acetone and alcohol to ultrasonically clean for 8-10 minutes and 3-5 minutes respectively to remove organic impurities on the surface, and then use deionized water to ultrasonically clean for 3-5 minutes. min, remove the inorganic impurities on the surface, and finally blow off the water vapor on the surface with a nitrogen gun.

Further, in step (4), the photolithography treatment is as follows: first apply the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, and then spin-coat the negative photoresist for 40-60 s, after pre-baking, exposure, post-baking, developing, hardening, and reactive ion etching with O ₂ plasma for 2-4 min, cleaning, and finally drying with hot nitrogen for 5-10 min.

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

Furthermore, the exposure is to place the pre-baked sample and photolithography mask on the photolithography machine at the same time, and then irradiate with an ultraviolet light source for 5-7 s.

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

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

Furthermore, the hardened film is heat-treated in an oven at 55-75°C for 6-8 minutes.

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

Further, in step (4), the electron beam evaporation plating electrode process is as follows: put the cleaned and dried insulating layer structure into the electron beam evaporation coating system, and the mechanical pump and the molecular pump vacuumize to 5.0~6.0 After ×10 ^-4 Pa, start to vapor-deposit the metal electrode, the metal evaporation rate is controlled at 2.0-3.0 Å/s, and the rotation speed of the sample plate is 10-20 r/min.

Further, in step (4), the degumming is soaked in acetone for 20-25 minutes and then ultrasonically treated for 1-3 minutes, thereby removing unnecessary parts and leaving the required interdigital electrode pattern.

Since the graphene surface of the complete lattice is not easy to absorb atoms with saturated dangling bonds, and there are dangling bonds on the surface of natural graphene where there are defects (nanoscale), this provides a natural nanovoid template for the growth of one-dimensional AlGaN nanocolumn array, 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 electrical conductivity, which 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 because of their simple structure, fast response speed, high photoresponsivity and many other advantages.

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

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

(2) AlGaN nanocolumn material is used as the active layer material in the AlGaN nanocolumn-based MSM type ultraviolet detector based on the graphene template of the present invention, because the band gap of the AlGaN material can vary from 3.4 eV to 3.4 eV according to the Al composition. It is continuously adjustable to 6.2eV, so it can effectively detect light with a wavelength of 200 nm to 365 nm, and has good solar blindness characteristics;

(3) The AlGaN nanocolumn-based MSM-type ultraviolet detector based on the graphene template of the present invention utilizes the huge specific surface area and quantum confinement of the one-dimensional nanocolumn material, which improves the density and transmission time of photogenerated carriers, Obtain high sensitivity and ultra-fast photoresponse;

(4) The AlGaN nanocolumn-based MSM type ultraviolet detector based on the graphene template of the present invention can realize highly sensitive detection of UVA-C ultraviolet light, and can be applied to the fields of ultraviolet missile guidance, open flame detection and solar illumination detection, etc., and is economical The benefits are considerable.

Description of drawings

Fig. 1 is the structural sectional schematic diagram of ultraviolet detector of the present invention;

Fig. 2 is the top view diagram of the electrode structure of the ultraviolet detector of the present invention;

Fig. 3 is that the Al composition that embodiment 1 prepares is based on the Al _0.02 Ga _0.98 N nano-column-based MSM type ultraviolet detector on the graphene template of 0.02 the electric current with the curve graph of the variation of applied bias;

Fig. 4 is that the Al component that embodiment 2 prepares is 0.3 based on the graphene template Al _0.3 Ga _0.7 N nano-column base MSM type ultraviolet detector's electric current changes with applied bias;

Fig. 5 is a graph showing the current variation curve of the MSM-type ultraviolet detector based on Al _0.98 Ga _0.02 N nano-column base on the graphene template with the Al composition of 0.98 prepared in Example 3 as a function of the applied bias voltage.

Detailed ways

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

In a specific embodiment, the structural cross-sectional schematic diagram of the AlGaN nano-column-based MSM type ultraviolet detector based on the graphene template of the present invention is shown in Figure 1, from bottom to top, including substrate 1, graphene template layer 2, AlGaN nano Column 3, Ni first metal layer 5 and Au second metal layer 6 forming Schottky contact with AlGaN nanocolumn, also includes Si ₃ N ₄ insulating layer 4 filled with AlGaN nanocolumn, Ni first metal layer 5 and The Au second metal layer 6 is used as an electrode material to form an interdigital electrode.

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 layers, and the thickness is 3-5 nm; the length of the AlGaN nanocolumn 3 is 300-500 nm, and the diameter is 100-5 nm. 200 nm; the first Ni metal layer and the Au second metal layer interdigitated electrode are Ni and Au metal layer interdigitated electrodes stacked sequentially from bottom to top, wherein the thickness of the first Ni metal layer 5 and the Au second metal layer 6 40-50 nm and 100-150 nm, respectively, the length of metal interdigitated 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.

Example 1

A preparation of an AlGaN nanocolumn-based MSM type ultraviolet detector with an Al component content of 0.02 on a graphene template (the nanocolumn is Al _0.02 Ga _0.98 N), specifically including the following steps:

(1) Clean the Si(111) substrate to remove residual pollutants and oxides on the surface, and place it in a plasma-enhanced chemical vapor deposition equipment to grow a graphene layer on the substrate surface to form a substrate/graphene structure , because 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) Direct growth of AlGaN nanocolumns on the substrate/graphene structure by PECVD method to form a substrate/graphene/AlGaN nanocolumn structure;

(3) On the substrate/graphene/AlGaN nanocolumn structure, the PECVD method is used to directly grow the Si ₃ N ₄ insulating layer to fill the gap between the AlGaN nanocolumns to form the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulation layer structure;

(4) Clean the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure, and then perform photolithography treatment, and use the electron beam evaporation coating system to sequentially evaporate two layers of Ni and Au on the surface of the sample The metal layer is used as an electrode, and the adhesive is removed to obtain a Ni/Au metal finger electrode in Schottky contact with the AlGaN layer, forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal finger Electrode structure, and transferred to the annealing furnace for thermal annealing;

(5) The substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigitated electrode structure is electroplated, press-welded, thinned, diced and wire bonded, and then packaged. Obtain the UV detector.

Further, in step (1), the cleaning is: ultrasonic cleaning with 6 wt% HF aqueous solution for 10 min to remove residual impurities on the surface, and then ultrasonic cleaning with acetone and absolute ethanol for 8 min and 5 min respectively, Remove organic impurities on the surface, then use deionized water to ultrasonically clean for 3 min, and finally blow off the water vapor on the surface with a nitrogen gun.

Further, in step (1), the process conditions for growing the graphene layer by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1.0×10 ^-4 Pa, heat the substrate to 950°C, stop Then the molecular pump was used to feed H ₂ and CH ₄ into the cavity, the flow rate was 150 sccm and 30 sccm respectively, the pressure was maintained at 100 Pa, and the RF plasma power was kept at 200 W during the deposition process. After the deposition, the substrate was heated in Ar gas Cooling to room temperature under the atmosphere, there are defect holes on the surface of the deposited graphene layer, so it is used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

Further, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1×10 ^-4 Pa, and the substrate/graphene structure is heated to At 950 ℃, Al powder and Ga balls were used as the Ga source and Al source of the AlGaN material. Then stop the molecular pump and then feed _N2 and _H2 into the chamber as carrier gas, the flow rate is 60 sccm and 20 sccm respectively, and _NH3 is fed as reaction gas, the flow rate is 20 sccm, and the RF plasma power is maintained during the growth process. At 250 W, the pressure in the reaction chamber was maintained at 50 Pa to deposit and form AlGaN nanopillars. After the deposition, the substrate was cooled to room temperature under _N2 gas atmosphere.

Furthermore, the heating temperatures of the Al powder and the Ga ball source region were 1000 °C and 950 °C, respectively, and Al _0.02 Ga _0.98 N nanocolumns with an Al composition of 0.02 were realized with a band gap of 3.46 eV.

Further, in step (3), the process conditions for growing the Si ₃ N ₄ insulating filling layer by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1.0×10 ^-4 Pa, and the substrate/graphene /AlGaN nanocolumn structure was heated to 550 °C, then the molecular pump was stopped and SiH ₄ and NH ₃ were introduced into the cavity, the flow rates were 20 sccm and 100 sccm respectively, and the RF plasma power was kept at 250 W during the growth process. The Si ₃ N ₄ insulating filling layer is deposited under a pressure maintained at 40 Pa.

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

Further, in step (4), the photolithography treatment is as follows: first apply the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, and then spin-coat the negative photoresist for 40 s with a homogenizer, After pre-baking, exposure, post-baking, development, film hardening, and reactive ion etching with O ₂ plasma for 4 min, cleaning, and finally hot nitrogen drying for 5 min.

Further, the pre-baking is heat treatment at 75°C for 5 min in an oven.

Furthermore, the exposure is to place the pre-baked sample and photolithography mask on the photolithography machine at the same time, and then irradiate with an ultraviolet light source for 5 s.

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

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

Furthermore, the hardened film is heat-treated at 75°C for 6 minutes in an oven.

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

Further, in step (4), the electron beam evaporation plating electrode process is as follows: put the cleaned and dried sample into the electronic book evaporation coating system, and vacuumize to 6.0×10 ^-4 Pa by the mechanical pump and the molecular pump , start to evaporate the metal electrode, the metal evaporation rate is controlled at 2.0 Å/s, and the sample disk rotates at 20 r/min

Further, in step (4), the gel removal is soaked in acetone for 20 min and then ultrasonically treated for 3 min, thereby removing unnecessary parts and leaving the desired interdigitated electrode pattern.

The prepared Al composition is 0.02 based on the graphene template AlGaN nano-column-based MSM type UV detector structure cross-sectional schematic diagram shown in Figure 1, wherein the thickness of Si (111) substrate 1 is 420 μm; graphene template layer The number of layers of 2 is 1 layer, and the thickness is 3 nm; the length of AlGaN nanocolumn 3 is 500 nm, and the diameter is 100 nm; the first metal layer of Ni and the second metal layer of Au are the interdigitated electrodes of Ni and Au from bottom to top Stacked metal interdigitated electrodes, wherein the thicknesses 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, and the electrode spacing is 10 μm, and the logarithm is 14 pairs. The schematic diagram of its top view is shown in Figure 2.

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

Example 2

A preparation of an AlGaN nanocolumn-based MSM type ultraviolet detector based on a graphene template with an Al composition of 0.3 (the nanocolumn is Al _0.3 Ga _0.7 N), specifically including the following steps:

(1) After cleaning the sapphire substrate to remove residual pollutants and oxides on the surface, place it in a plasma-enhanced chemical vapor deposition (PECVD) device to grow a graphene layer on the substrate surface to form a substrate/graphene structure , because 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) Direct growth of AlGaN nanocolumns on the substrate/graphene structure by PECVD method to form a substrate/graphene/AlGaN nanocolumn structure;

(3) On the substrate/graphene/AlGaN nanocolumn structure, the PECVD method is used to directly grow the Si ₃ N ₄ insulating layer to fill the gap between the AlGaN nanocolumns to form the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulation layer structure;

(4) Clean the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure, and then perform photolithography treatment, and use the electron beam evaporation coating system to sequentially evaporate two layers of Ni and Au on the surface of the sample The metal layer is used as an electrode, and the adhesive is removed to obtain a Ni/Au metal finger electrode in Schottky contact with the AlGaN layer, forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal finger Electrode structure, and transferred to the annealing furnace for thermal annealing;

(5) The substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigitated electrode structure is electroplated, press-welded, thinned, diced and wire bonded, and then packaged. Obtain the UV detector.

Further, in step (1), the cleaning is: ultrasonic cleaning with 8 wt% HF aqueous solution for 9 min to remove residual impurities on the surface, followed by ultrasonic cleaning with acetone and absolute ethanol for 10 min and 4 min respectively, Remove organic impurities on the surface, then use deionized water to ultrasonically clean for 5 min, and finally blow off the water vapor on the surface with a nitrogen gun.

Further, in step (1), the process conditions for growing the graphene layer by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 2×10 ^-4 Pa, heat the substrate to 1000 °C, stop Then the molecular pump was used to feed H ₂ and CH ₄ into the cavity, the flow rates were 120 sccm and 25 sccm respectively, the pressure was maintained at 70 Pa, and the RF plasma power was kept at 300 W during the deposition process. After the deposition, the substrate was heated in Ar gas Cooling to room temperature under the atmosphere, there are defect holes on the surface of the deposited graphene layer, so it is used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

Further, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1.5×10 ^-4 Pa, and the substrate/graphene structure is heated to At 900 ℃, Al powder and Ga balls were used as the Al source and Ga source of the AlGaN material. Then stop the molecular pump and then feed _N2 and _H2 into the cavity as carrier gas, the flow rates are 80 sccm and 25 sccm respectively, and _NH3 is introduced as reaction gas, the flow rate is 22 sccm, and the radio frequency plasma power is maintained during the growth process. At 150 W, the pressure in the reaction chamber was maintained at 75 Pa to deposit and form AlGaN nanopillars. After the deposition, the substrate was cooled to room temperature under _N2 gas atmosphere.

Furthermore, the heating temperatures of the Al powder and the Ga ball source region are 1050°C and 930°C respectively, so that the Al composition of AlGaN is 0.3 and the band gap is about 4.20 eV.

Further, in step (3), the process conditions for growing the Si ₃ N ₄ insulating filling layer by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 2×10 ^-4 Pa, and the substrate/graphene /AlGaN nanocolumn structure was heated to 500 °C, then the molecular pump was stopped and SiH ₄ and NH ₃ were introduced into the chamber with flow rates of 30 sccm and 150 sccm respectively. During the growth process, the RF plasma power was kept at 280 W, and the reaction chamber The Si ₃ N ₄ insulating filling layer is deposited under a pressure maintained at 90 Pa.

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

Further, in step (4), the photolithography treatment is as follows: first coat the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, and then spin-coat the negative photoresist for 50 s with a homogenizer, After pre-baking, exposure, post-baking, developing, film hardening, and reactive ion etching with O ₂ plasma for 3 minutes, cleaning, and finally drying with hot nitrogen for 10 minutes.

Furthermore, the pre-baking is heat treatment at 70°C for 8 min in an oven.

Furthermore, the exposure is to place the pre-baked sample and photolithography mask on the photolithography machine at the same time, and then irradiate with an ultraviolet light source for 7 s.

Furthermore, the post-baking is heat treatment at 95°C for 2.5 minutes in an oven.

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

Furthermore, the hardened film is heat-treated at 55°C for 8 minutes in an oven.

Furthermore, the cleaning is 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.

Further, in step (4), the electron beam evaporation plating electrode process is as follows: put the cleaned and dried sample into the electronic book evaporation coating system, and vacuumize to 5.5×10 ^-4 Pa by the mechanical pump and the molecular pump , start to evaporate the metal electrode, the metal evaporation rate is controlled at 3.0 Å/s, and the sample disk rotates at 10 r/min

Further, in step (4), the gel removal is soaked in acetone for 25 minutes and then ultrasonically treated for 2 minutes, thereby removing unnecessary parts and leaving the desired interdigitated electrode pattern.

The prepared Al composition is 0.3 based on the graphene template AlGaN nano-column-based MSM type UV detector structure cross-sectional schematic diagram shown in Figure 1, wherein the thickness of Si (111) substrate 1 is 430 μm; graphene template layer The number of layers of 2 is 3 layers, and the thickness is 5 nm; the length of AlGaN nanocolumn 3 is 300 nm, and the diameter is 200 nm; the first metal layer of Ni and the second metal layer of Au are the interdigitated electrodes of Ni and Au from bottom to top Stacked metal layer interdigitated electrodes, wherein the thicknesses 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, and the electrode spacing is 15 μm, and the logarithm is 12 pairs.

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

Example 3

A preparation of an AlGaN nanocolumn-based MSM type ultraviolet detector based on a graphene template with an Al composition of 0.98 (the nanocolumn is Al _0.98 Ga _0.02 N), specifically including the following steps:

(1) After cleaning the La _0.3 Sr _1.7 AlTaO ₆ substrate to remove residual pollutants and oxides on the surface, place it in a plasma-enhanced chemical vapor deposition (PECVD) device to grow a graphene layer on the substrate surface to form a lining Bottom/graphene structure, because there are defects and 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) Direct growth of AlGaN nanocolumns on the substrate/graphene structure by PECVD method to form a substrate/graphene/AlGaN nanocolumn structure;

(3) On the substrate/graphene/AlGaN nanocolumn structure, the PECVD method is used to directly grow the Si ₃ N ₄ insulating layer to fill the gap between the AlGaN nanocolumns to form the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulation layer structure;

(4) Clean the substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure, and then perform photolithography treatment, and use the electron beam evaporation coating system to sequentially evaporate two layers of Ni and Au on the surface of the sample The metal layer is used as an electrode, and the adhesive is removed to obtain a Ni/Au metal finger electrode in Schottky contact with the AlGaN layer, forming a substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal finger Electrode structure, and transferred to the annealing furnace for thermal annealing;

(5) The substrate/graphene/AlGaN nanocolumn/Si ₃ N ₄ insulating layer structure/Ni/Au metal interdigitated electrode structure is electroplated, press-welded, thinned, diced and wire bonded, and then packaged. Obtain the UV detector.

Further, in step (1), the cleaning is: ultrasonic cleaning with 10 wt% HF aqueous solution for 8 minutes to remove residual impurities on the surface, and then ultrasonic cleaning with acetone and absolute ethanol for 9 minutes and 3 minutes respectively, The organic impurities on the surface were removed, followed by ultrasonic cleaning with deionized water for 4 min, and finally the water vapor on the surface was blown away with a nitrogen gun.

Further, in step (1), the process conditions for growing the graphene layer by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1.5×10 ^-4 Pa, heat the substrate to 980°C, stop Then the molecular pump was used to feed H ₂ and CH ₄ into the cavity, the flow rate was 80 sccm and 20 sccm respectively, the pressure was maintained at 30 Pa, and the RF plasma power was kept at 250 W during the deposition process. After the deposition, the substrate was heated in Ar gas Cooling to room temperature under the atmosphere, there are defect holes on the surface of the deposited graphene layer, so it is used as a template layer for the self-growth of AlGaN nanocolumns in the next step;

Further, in step (2), the process conditions for growing AlGaN nanocolumns by PECVD are: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 2×10 ^-4 Pa, and the substrate/graphene structure is heated to At 850 ℃, Al powder and Ga balls are used as the Al source and Ga source of AlGaN material. Then stop the molecular pump and then feed _N2 and _H2 into the cavity as carrier gas, the flow rate is 100 sccm and 30 sccm respectively, and _NH3 is fed as reaction gas, the flow rate is 30 sccm, and the RF plasma power is maintained during the growth process. At 200 W, the pressure in the reaction chamber was maintained at 100 Pa to deposit and form AlGaN nanopillars. After the deposition, the substrate was cooled to room temperature under _N2 gas atmosphere.

Furthermore, the heating temperatures of the Al powder and the Ga ball source region are 1100 °C and 850 °C respectively, and the Al composition of the AlGaN nanocolumn is 0.98, and the Al _0.98 Ga _0.02 N band gap is 6.14 eV.

Further, in step (3), the process conditions for growing the Si ₃ N ₄ insulating filling layer by PECVD are as follows: use a mechanical pump and a molecular pump to evacuate until the pressure inside the quartz tube is maintained at 1.5×10 ^-4 Pa, and the substrate/graphene /AlGaN nanocolumn structure was heated to 450 °C, then the molecular pump was stopped and SiH ₄ and NH ₃ were introduced into the cavity with flow rates of 25 sccm and 130 sccm respectively. During the growth process, the RF plasma power was kept at 300 W, and the reaction chamber The Si ₃ N ₄ insulating filling layer is deposited under a pressure maintained at 80 Pa.

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

Further, in step (4), the photolithography treatment is as follows: first apply the adhesion promoter HMDS to enhance the adhesion between the silicon wafer and the photoresist, and then spin-coat the negative photoresist for 60 s with a homogenizer, After pre-baking, exposure, post-baking, development, film hardening, and reactive ion etching with O ₂ plasma for 2 min, cleaning, and finally hot nitrogen drying for 8 min.

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

Furthermore, the exposure is to place the pre-baked sample and photolithography mask on the photolithography machine at the same time, and then irradiate with an ultraviolet light source for 6.5 s.

Furthermore, the post-baking is heat treatment at 90°C for 2 min in an oven.

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

Furthermore, the hardened film is heat-treated at 65°C for 7 minutes in an oven.

Furthermore, the cleaning was ultrasonically cleaned with deionized water for 4 minutes to remove inorganic impurities on the surface, and finally the water vapor on the surface was blown away with a nitrogen gun.

Further, in step (4), the electron beam evaporation plating electrode process is as follows: put the cleaned and dried sample into the electronic book evaporation coating system, and vacuumize to 5.0×10 ^-4 Pa by the mechanical pump and the molecular pump , start to evaporate the metal electrode, the metal evaporation rate is controlled at 2.5 Å/s, and the sample disk rotates at 12 r/min

Further, in step (4), the gel removal is soaked in acetone for 22 minutes and then ultrasonically treated for 1 minute, thereby removing unnecessary parts and leaving the desired interdigitated electrode pattern.

The prepared AlGaN nanocolumn-based MSM type ultraviolet detector with an Al composition of 0.98 is shown in Figure 5. The current increases with the increase of the applied bias voltage. Large, and the image has good symmetry in the positive and negative pressure regions, indicating that a good Schottky contact is formed. Under the bias voltage of 1 V, the dark current is only 16.4nA, indicating that the prepared photodetector has good dark current characteristics, and the current increases significantly (~μA) under the irradiation of 200 nm light, indicating that the photodetector has the ability to resist UVC ultraviolet light. Very sensitive detection effect.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (10)

1. one kind is based on AlGaN nanometers of base for post MSM type ultraviolet detectors in graphene template, which is characterized in that including by down toward On substrate (1), graphene template layer (2), AlGaN nano-pillar (3), the Ni for forming with AlGaN nano-pillar Schottky contacts One metal layer (5) and Au second metal layer (6) further include the Si filled in AlGaN nano-pillar₃N₄Insulating layer (4), and Ni first Metal layer (5) and Au second metal layer (6) are as electrode material composition interdigital electrode.

2. according to claim 1 based on AlGaN nanometers of base for post MSM type ultraviolet detectors in graphene template, feature It is, the substrate (1) is sapphire, Si or La_0.3Sr_1.7AlTaO₆Substrate, and substrate (1) with a thickness of 420 ~ 430 μm； The number of plies of the graphene template layer (2) is 1 ~ 3 layer, with a thickness of 3 ~ 5 nm；AlGaN nano-pillar (3) length is 300 ~ 500 Nm, diameter are 100 ~ 200 nm；The Ni the first metal layer (5) with a thickness of 40 ~ 50 nm, the thickness of Au second metal layer (6) For 100 ~ 150 nm；The length of the interdigital electrode is 280 ~ 340 μm, and width is 10 ~ 15 μm, and electrode spacing is 10 ~ 15 μ M, logarithm are 12 ~ 20 pairs.

3. the described in any item systems based on AlGaN nanometers of base for post MSM type ultraviolet detectors in graphene template of claim 1 ~ 2 Preparation Method, which comprises the steps of:

(1) it is grown graphene template layer (2) after cleaning substrate on substrate (1) surface, forms substrate/graphene-structured；

(2) growth obtains AlGaN nano-pillar (3) in substrate/graphene-structured described in step (1), forms substrate/graphite Alkene/AlGaN nanometers of rod structure；

(3) Si is grown on the substrate described in step (2)/graphene/AlGaN nanometers of rod structure₃N₄Insulating layer (4) fills AlGaN Gap between nano-pillar (3) forms substrate/graphene/AlGaN nano-pillar/Si₃N₄Insulation layer structure；

(4) to substrate/graphene described in step (3)/AlGaN nano-pillar/Si₃N₄Insulation layer structure starts the cleaning processing, then into After row photoetching treatment, two layers of gold medal of Ni and Au is successively deposited on the insulation layer structure surface using electron beam evaporation deposition system Belong to layer as electrode, remove photoresist, obtain the Ni/Au metal interdigital electrode with AlGaN nano-pillar Schottky contacts, forms substrate/stone Black alkene/AlGaN nano-pillar/Si₃N₄Insulation layer structure/Ni/Au metal interdigitated electrode structure, and carry out thermal anneal process；

(5) by substrate/graphene described in step (4)/AlGaN nano-pillar/Si₃N₄Insulation layer structure/interdigital the electricity of Ni/Au metal Pole structure carries out plating pressure welding point, thinned, scribing and wire bonding, then is packaged, and obtains the MSM type ultraviolet detection Device.

4. preparation method according to claim 3, which is characterized in that in the step (1), the cleaning are as follows: using 6 ~ The HF aqueous solution of 10wt% is cleaned by ultrasonic 8 ~ 10 min, removes the residual impurity object on surface, then successively with acetone ultrasonic cleaning 8 ~ 10 min and dehydrated alcohol are cleaned by ultrasonic 3 ~ 5 min, remove the organic impurities on surface, are then cleaned by ultrasonic using deionized water 3 ~ 5 min finally blow away the steam on surface with nitrogen gun.

5. preparation method according to claim 3, which is characterized in that in step (1), graphene layer is grown using PECVD, And process conditions are as follows: be evacuated to quartzy overpressure using mechanical pump and molecular pump and be maintained 1 ~ 2 × 10^-4 Pa, silicon To 950 ~ 1000 DEG C, then the molecular pump that stops is passed through H into cavity₂And CH₄, H₂Flow is 80 ~ 150 sccm, CH₄Flow is 20 ~ 30 sccm, pressure are maintained 30 ~ 100 Pa, and RF plasma power is maintained at 200 ~ 300 W in deposition process, sink Product terminates back substrate and is cooled to room temperature under Ar gas atmosphere.

6. preparation method according to claim 3, which is characterized in that in the step (2), grow AlGaN using PECVD Nano-pillar, and process conditions are as follows: be evacuated to quartzy overpressure using mechanical pump and molecular pump and be maintained 1 ~ 2 × 10^-4 Pa, Substrate/graphene-structured is heated to 850 ~ 950 DEG C, the source Al and the source Ga using Al powder and Ga ball as AlGaN material, by Al Powder is heated to 1000 ~ 1100 DEG C；Ga ball is heated to 850 ~ 950 DEG C；Then the molecular pump that stops is passed through N into cavity₂And H₂Make For carrier gas, flow is respectively 60 ~ 100 sccm and 20 ~ 30 sccm, is passed through NH₃As reaction gas, flow is 20 ~ 30 Sccm, RF plasma power is maintained at 150 ~ 250 W in growth course, and reaction room pressure is maintained under 50 ~ 100 Pa Deposition forms AlGaN nano-pillar, and deposition terminates back substrate in N₂It is cooled to room temperature under gas atmosphere.

7. preparation method according to claim 3, which is characterized in that in the step (3), grow Si using PECVD₃N₄ Insulation fill stratum, and process conditions are as follows: be evacuated to quartzy overpressure using mechanical pump and molecular pump and be maintained 1 ~ 2 × 10^-4 Pa, substrate/graphene/AlGaN nanometers of rod structure are heated to 450 ~ 550 DEG C, then the molecular pump that then stops is passed through into cavity SiH₄And NH₃, SiH₄Flow is 20 ~ 30 sccm, NH₃Flow is 100 ~ 150 sccm, radio frequency plasma function in growth course Rate is maintained at 250 ~ 300 W, and reaction room pressure, which is maintained under 40 ~ 90 Pa, deposits Si₃N₄Insulation fill stratum.

8. preparation method according to claim 3, which is characterized in that in the step (4), cleaning treatment are as follows: first successively Be cleaned by ultrasonic 8 ~ 10 min and alcohol with acetone and be cleaned by ultrasonic 3 ~ 5 min, remove the organic impurities on surface, then using go from Sub- water is cleaned by ultrasonic 3 ~ 5 min, removes the inorganic impurity on surface, the steam on surface is finally blown away with nitrogen gun.

9. preparation method according to claim 3, which is characterized in that in the step (4), photoetching treatment are as follows: first coat Tackifier HMDS, recycle 40 ~ 60 s of sol evenning machine spin coating negative photoresist, through front baking, exposure, after dry, develop and post bake, and Using O₂Plasma carries out reactive ion etching and handles 2 ~ 4 min, cleaning, and last hot nitrogen dries 5 ~ 10 min；

The front baking is to carry out 65 ~ 75 DEG C of 5 ~ 8 min of heat treatment in an oven；

The exposure is to be placed on front baking treated sample and lithography mask version on litho machine simultaneously, then ultraviolet source photograph Penetrate 5 ~ 7 s；

Dry after described is to carry out 85 ~ 95 DEG C of 2 ~ 3 min of heat treatment in an oven；

The development be by it is rear dry that treated sample be put into it is molten in the tetrabutylammonium hydroxide aqueous solution developer solution of 6 ~ 8 wt% Solve 60 ~ 100 s；

The post bake is to carry out 55 ~ 75 DEG C of 6 ~ 8 min of heat treatment in an oven；

The cleaning is to be cleaned by ultrasonic 3 ~ 5 min using deionized water, removes the inorganic impurity on surface, is finally blown away with nitrogen gun The steam on surface.

10. preparation method according to claim 3, which is characterized in that in the step (4), electron beam evaporation plated electrode Technique are as follows: the insulation layer structure of cleaned drying is put into electron beam evaporation deposition system, mechanical pump and molecule pumping Vacuum is to 5.0 ~ 6.0 × 10^-4 After Pa, start evaporation metal electrode, evaporation of metal rate control is 2.0 ~ 3.0/s, sample disc Revolving speed is 10 ~ 20 r/min；Remove photoresist is to be ultrasonically treated 1 ~ 3 min after impregnating 20 ~ 25 min in acetone.