CN113948604B - Three-dimensional structure high-gain AlGaN solar blind ultraviolet detector and preparation method thereof - Google Patents

Abstract

The invention provides a three-dimensional structure high-gain AlGaN solar blind ultraviolet detector, which belongs to the technical field of ultraviolet detection and comprises a substrate, and a buffer layer, an n-AlGaN layer, an i-AlGaN layer and a p-AlGaN layer which are sequentially grown on the substrate; the areas of the i-AlGaN layer and the p-AlGaN layer, which are positioned between the active areas of the device, are etched away to form two separated p-type active areas; the p-type active region is arranged on the p-AlGaN layer, and the p-type active region is arranged on the p-AlGaN layer; the n-AlGaN layer is used as a base electrode to be connected with two pin structures to form a p-i-n-i-p structure, electrons are gathered in the n-AlGaN layer under illumination, potential barriers between the base electrode of the n-AlGaN layer and the p-AlGaN layer are reduced, holes are emitted in the p-AlGaN layer, and gain is generated. The invention also provides a preparation method of the detector. The detector has the characteristics of high response speed, excellent performance, simple structure, simple preparation method and wide application prospect while having high gain.

Description

A three-dimensional high-gain AlGaN solar-blind ultraviolet detector and its preparation method

Technical Field

The invention relates to the technical field of ultraviolet detection, and in particular to a three-dimensional high-gain AlGaN solar-blind ultraviolet detector and a preparation method thereof.

Background technique

Solar radiation with a wavelength between 200nm and 280nm is absorbed by the atmosphere and rarely reaches the earth's surface, so this wavelength range is called the solar-blind ultraviolet region. Due to the low background noise, solar-blind ultraviolet detectors have the advantages of low false alarm rate and high detection efficiency. They have important applications in flame sensing, ozone detection, confidential communications, missile warning and other fields. The bandgap width of AlGaN material is continuously adjustable from 3.4eV to 6.2eV. By reasonably adjusting the Al component content, effective solar-blind zone ultraviolet detection (200nm-280nm) can be achieved. At the same time, it has the advantages of high carrier mobility, low surface recombination rate, and strong chemical stability. Therefore, AlGaN material is one of the preferred materials for preparing solar-blind ultraviolet detectors. According to theoretical calculation results, solar-blind ultraviolet detection characteristics can only be guaranteed when the Al component in AlGaN material is higher than 0.45. However, it is very difficult to grow AlGaN materials with high Al components (especially Al components around 0.5). The main reasons are low mobility of Al atoms and serious pre-reaction of Al sources. Therefore, there are high-density defects in AlGaN solar-blind ultraviolet detector materials, which reduces the performance of AlGaN solar-blind ultraviolet detectors and restricts their development and application. How to design new devices from the perspective of optimizing devices is the key to improving AlGaN solar-blind ultraviolet detectors.

At present, AlGaN day-blind ultraviolet detectors with various structures are being studied, including metal-semiconductor-metal (MSM), Schottky, p-n junction and avalanche multiplier detector (APD). Schottky, MSM and p-n junction have fast response rates, but do not have the characteristics of gain, making it difficult to detect weak signals. There are usually two types of detectors with gain, namely photoelectric and APD, but the photoconductive detector has a slow response speed; APD has very high requirements on the quality of AlGaN materials and the efficiency of P-type and N-type doping, and the existing material growth methods are difficult to meet its requirements. At the same time, APD has strict requirements on device technology, which seriously limits the development and application of AlGaN-APD detectors.

In view of this, it is urgent to study a new type of high-gain AlGaN solar-blind ultraviolet detector structure and its preparation method to solve the problems faced by the existing traditional structure AlGaN solar-blind ultraviolet detector.

Summary of the invention

In view of this, the present invention provides a three-dimensional high-gain AlGaN solar-blind ultraviolet detector and a preparation method thereof, and designs a new three-dimensional (3D) p-i-n-i-p structured AlGaN solar-blind ultraviolet detector, which has high gain characteristics, can realize weak signal detection, and has a fast response time, and has a simple preparation process and broad application prospects.

To achieve the above object, the present invention provides a three-dimensional structure high-gain AlGaN solar-blind ultraviolet detector, comprising a substrate, a buffer layer, an n-AlGaN layer, an i-AlGaN layer, and a p-AlGaN layer sequentially grown on the substrate;

The regions of the i-AlGaN layer and the p-AlGaN layer located between the active regions of the device are etched away to form two separated p-type active regions with an isolation width of 0.01-1000 μm;

It also includes two upper electrodes, both of which are p-type ohmic contact electrodes, which are respectively located above the p-AlGaN layers of the two p-type active regions, and the upper electrodes form ohmic contacts with the p-AlGaN layers;

The n-AlGaN layer serves as a base to connect the two parts of the pin structure to form a p-i-n-i-p structure. Under light irradiation, electrons gather in the n-AlGaN layer, reducing the potential barrier between the n-AlGaN layer base and the p-AlGaN layer, causing holes to be emitted in the p-AlGaN layer, generating gain.

Furthermore, the substrate is a heterogeneous substrate or a homogeneous substrate.

Furthermore, the material of the heterogeneous substrate is any one of sapphire, silicon carbide, and silicon; and the material of the homogeneous substrate is GaN or AlN.

Furthermore, in the n-AlGaN layer, the i-AlGaN layer and the p-AlGaN layer, the content of the Al component is in the range of 0-1.

Furthermore, the material of the upper electrode is any one of Pt, Ni, Au, and ITO.

The present invention also provides a method for preparing the three-dimensional high-gain AlGaN solar-blind ultraviolet detector as described above, comprising the following steps:

S1: growing device epitaxial materials: sequentially growing the buffer layer, n-AlGaN layer, i-AlGaN layer and p-AlGaN layer on the substrate;

S2: preparing the device active area structure: using PECVD technology to grow a mask layer on the outermost layer of the device epitaxial material, using photolithography technology to depict the device mesa pattern on the mask layer, using RIE technology to etch and remove the mask layer in the non-mesa area that is not covered by the photoresist, using ICP technology to etch the area not covered by the mask layer to the n-AlGaN layer, and using HF to remove the mask layer in the mesa area;

S3: Preparation of electrodes: Photolithography technology is used to prepare photoresist mask patterns of two upper electrodes on top of the two parts of the p-AlGaN layer. After development, the photoresist in the electrode pattern area is removed, and the photoresist in the non-electrode area is retained. Then, p-type ohmic electrode material is evaporated on the photoresist mask pattern, and the Lift Off technology is used to remove the photoresist and the electrode material covering the upper part, and finally a rapid annealing treatment is performed.

Furthermore, the method for growing the device epitaxial material in step S1 is any one of MOCVD, MBE, and HVPE;

The material of the mask layer in step S2 is any one of SiO ₂ , Si, and Ni.

Furthermore, in the step S2, photolithography technology is used, and the selection of positive and negative resists is determined according to the design of the photoresist pattern window, so that after development, the photoresist in the detector photosensitive surface area is retained, and the photoresist in the non-detector photosensitive surface area is removed;

In the step S3, photolithography technology is used, and the selection of positive and negative resists is determined according to the design of the photoresist pattern window, so that after development, the photoresist in the incident window area is removed, and the photoresist in the remaining parts is retained.

Furthermore, in step S3, the method used for evaporating the p-type ohmic contact electrode material is any one of electron beam evaporation, thermal evaporation technology, and magnetron sputtering technology; the thickness of the evaporated p-type ohmic electrode material is 100-300nm.

Furthermore, in step S3, the photoresist is dissolved and removed by using the Lift Off technology, and the dissolving liquid is an acetone solution;

The rapid annealing treatment is to anneal the p-type ohmic contact electrode in a nitrogen atmosphere using a rapid annealing furnace. The annealing temperature and time are determined by the electrode material.

The three-dimensional high-gain AlGaN solar-blind ultraviolet detector of the present invention and its preparation method are based on a pin-structured AlGaN epitaxial wafer, and a p-i-n-i-p structure is formed by photolithography and etching, and a 3D structure AlGaN detector is formed by processes such as electrode evaporation. It is a new detector structure. Under ultraviolet light, electrons gather in the n-AlGaN layer, reducing the potential barrier between the base of the n-AlGaN layer and the p-AlGaN layer, causing holes to be emitted in the p-AlGaN layer, generating gain; the gain of the detector with the above structure is caused by carrier emission, so it has a high gain and a fast response speed. The three-dimensional high-gain AlGaN solar-blind ultraviolet detector of the present invention has excellent performance, simple structure, simple preparation method, and broad application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of the structure of a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to the present invention;

FIG2 is a schematic diagram of a process flow for preparing a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to the present invention;

Explanation of the reference numerals: 1 - substrate; 2 - buffer layer; 3 - n-AlGaN layer; 4 - i-AlGaN layer; 5 - p-AlGaN layer; 6 - upper electrode.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The present invention provides a three-dimensional high-gain AlGaN solar-blind ultraviolet detector, as shown in FIG1 , comprising a substrate 1, a buffer layer 2, an n-AlGaN layer 3, an i-AlGaN layer 4, and a p-AlGaN layer 5 sequentially grown on the substrate 1;

The regions between the i-AlGaN layer 4 and the p-AlGaN layer 5 located in the active region of the device are etched away to form two separated p-type active regions, with an isolation width of 0.01-1000 μm, preferably 1 μm;

It also includes two upper electrodes 6, both of which are p-type ohmic contact electrodes, which are respectively located above the p-AlGaN layer 5 of the two p-type active regions, and the upper electrodes 6 form ohmic contacts with the p-AlGaN layer 5;

The n-AlGaN layer 3 serves as a base to connect the two parts of the pin structure to form a p-i-n-i-p structure. Under light, electrons gather in the n-AlGaN layer 3, reducing the potential barrier between the base of the n-AlGaN layer 3 and the p-AlGaN layer 5, causing holes to be emitted in the p-AlGaN layer 5, generating gain.

The substrate 1 may be a heterogeneous substrate or a homogeneous substrate. When it is a heterogeneous substrate, the material may be selected from any one of sapphire, silicon carbide, silicon, etc.; when it is a homogeneous substrate, the material may be selected from GaN or AlN.

The content of Al in the n-AlGaN layer 3, the i-AlGaN layer 4 and the p-AlGaN layer 5 is 0 to 1. The material of the upper electrode 6 can be any one of Pt, Ni, Au, ITO and other materials that can form an ohmic contact with the p-type GaN material.

The present invention also provides a method for preparing the three-dimensional high-gain AlGaN solar-blind ultraviolet detector as described above, as shown in FIG2 , comprising the following steps:

S1: growing device epitaxial materials: sequentially growing the buffer layer 2, the n-AlGaN layer 3, the i-AlGaN layer 4 and the p-AlGaN layer 5 on the substrate 1;

S2: preparing the device active area structure: using PECVD technology to grow a mask layer on the outermost layer of the device epitaxial material, using photolithography technology to depict the device mesa pattern on the mask layer, using RIE technology to etch and remove the mask layer in the non-mesa area that is not covered by the photoresist, using ICP technology to etch the area not covered by the mask layer to the n-AlGaN layer, and using HF to remove the mask layer in the mesa area;

S3: preparing electrodes: using photolithography technology to prepare photoresist mask patterns of two upper electrodes 6 on the two parts of the p-AlGaN layer 5, removing the photoresist in the electrode pattern area after development, and retaining the photoresist in the non-electrode area, then vapor-depositing a p-type ohmic electrode material on the photoresist mask pattern, and then using Lift Off technology to remove the photoresist and the electrode material covering the upper part, and finally performing rapid annealing treatment.

The method for growing the device epitaxial material in step S1 is any one of MOCVD, MBE, HVPE, etc. The material of the mask layer in step S2 is any one of SiO ₂ , Si, Ni, etc.

In the step S2, photolithography technology is used, and the selection of positive and negative resists is determined according to the design of the photoresist pattern window, so that after development, the photoresist in the detector photosensitive surface area is retained, and the photoresist in the non-detector photosensitive surface area is removed. In the step S3, photolithography technology is used, and the selection of positive and negative resists is determined according to the design of the photoresist pattern window, so that after development, the photoresist in the incident window area is removed, and the photoresist in the rest of the parts is retained.

The method used for evaporating the p-type ohmic contact electrode material in step S3 is any one of electron beam evaporation, thermal evaporation technology, magnetron sputtering technology, etc. The thickness of the evaporated p-type ohmic electrode material is preferably 100-300 nm.

In step S3, the photoresist is dissolved and removed by using the Lift Off technology, and the dissolving liquid is an acetone solution. The rapid annealing treatment is to anneal the p-type ohmic contact electrode in a nitrogen atmosphere using a rapid annealing furnace, and the annealing temperature and time are determined by the electrode material.

The three-dimensional high-gain AlGaN solar-blind ultraviolet detector of the present invention and its preparation method are based on a pin-structured AlGaN epitaxial wafer, and a p-i-n-i-p structure is formed by photolithography and etching, and a 3D structure AlGaN detector is formed by processes such as electrode evaporation. It is a new detector structure. Under ultraviolet light, electrons gather in the n-AlGaN layer, reducing the potential barrier between the base of the n-AlGaN layer and the p-AlGaN layer, causing holes to be emitted in the p-AlGaN layer, generating gain; the gain of the detector with the above structure is caused by carrier emission, so it has a high gain and a fast response speed. The three-dimensional high-gain AlGaN solar-blind ultraviolet detector of the present invention has excellent performance, simple structure, simple preparation method, and broad application prospects.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A three-dimensional high-gain AlGaN solar-blind ultraviolet detector, characterized in that it comprises a substrate, a buffer layer, an n-AlGaN layer, an i-AlGaN layer, and a p-AlGaN layer sequentially grown on the substrate; the content of Al component in the n-AlGaN layer, the i-AlGaN layer, and the p-AlGaN layer is greater than 0.45; The regions of the i-AlGaN layer and the p-AlGaN layer located between the active regions of the device are etched away to form two separated p-type active regions with an isolation width of 0.01-1000 μm; It also includes two upper electrodes, both of which are p-type ohmic contact electrodes, which are respectively located above the p-AlGaN layers of the two p-type active regions, and the upper electrodes form ohmic contacts with the p-AlGaN layers; The n-AlGaN layer serves as a base to connect the two parts of the pin structure to form a p-i-n-i-p structure. Under light irradiation, electrons gather in the n-AlGaN layer, reducing the potential barrier between the n-AlGaN layer base and the p-AlGaN layer, causing holes to be emitted in the p-AlGaN layer, generating gain. 2 . The three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 1 , wherein the substrate is a heterogeneous substrate or a homogeneous substrate. 3. The three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 2 is characterized in that the material of the heterogeneous substrate is any one of sapphire, silicon carbide, and silicon; the material of the homogeneous substrate is GaN or AlN. 4. The three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 1 is characterized in that the material of the upper electrode is any one of Pt, Ni, Au, and ITO. 5. A method for preparing a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to any one of claims 1 to 4, characterized in that it comprises the following steps: S1: growing device epitaxial materials: sequentially growing the buffer layer, n-AlGaN layer, i-AlGaN layer and p-AlGaN layer on the substrate; S2: preparing the device active area structure: using PECVD technology to grow a mask layer on the outermost layer of the device epitaxial material, using photolithography technology to depict the device mesa pattern on the mask layer, using RIE technology to etch and remove the mask layer in the non-mesa area that is not covered by the photoresist, using ICP technology to etch the area not covered by the mask layer to the n-AlGaN layer, and using HF to remove the mask layer in the mesa area; S3: Preparation of electrodes: Photolithography technology is used to prepare photoresist mask patterns of two upper electrodes on top of the two parts of the p-AlGaN layer. After development, the photoresist in the electrode pattern area is removed, and the photoresist in the non-electrode area is retained. Then, p-type ohmic electrode material is evaporated on the photoresist mask pattern, and the Lift Off technology is used to remove the photoresist and the electrode material covering the upper part, and finally a rapid annealing treatment is performed. 6. The method for preparing a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 5, characterized in that the method for growing the device epitaxial material in step S1 is any one of MOCVD, MBE, and HVPE; The material of the mask layer in step S2 is any one of SiO ₂ , Si, and Ni. 7. The method for preparing a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 5, characterized in that the photolithography technology is used in the step S2, and the selection of positive and negative resists is determined according to the design of the photoresist pattern window, so that the photoresist in the detector photosensitive surface area is retained after development, and the photoresist in the non-detector photosensitive surface area is removed; In the step S3, photolithography technology is used, and the selection of positive and negative resists is determined according to the design of the photoresist pattern window, so that after development, the photoresist in the incident window area is removed, and the photoresist in the remaining parts is retained. 8. The method for preparing a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 5 is characterized in that the method used for evaporating the p-type ohmic contact electrode material in step S3 is any one of electron beam evaporation, thermal evaporation technology, and magnetron sputtering technology; the thickness of the evaporated p-type ohmic electrode material is 100-300nm. 9. The method for preparing a three-dimensional high-gain AlGaN solar-blind ultraviolet detector according to claim 5, characterized in that the photoresist is dissolved and removed by using a Lift Off technique in step S3, and an acetone solution is used as the dissolving liquid; The rapid annealing treatment is to anneal the p-type ohmic contact electrode in a nitrogen atmosphere using a rapid annealing furnace. The annealing temperature and time are determined by the electrode material.