CN210866245U

CN210866245U - Gallium nitride micron line array photoelectric detector

Info

Publication number: CN210866245U
Application number: CN201921617846.4U
Authority: CN
Inventors: 高芳亮; 刘青; 李述体; ***; 罗幸君; 孙一鸣; 施江
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2019-09-26
Filing date: 2019-09-26
Publication date: 2020-06-26
Anticipated expiration: 2029-09-26

Abstract

The utility model discloses a gallium nitride micron line array photoelectric detector, this photoelectric detector includes: a silicon substrate, a methyl amino lead iodide layer and an electrode; a plurality of grooves which are arranged in parallel are formed on the upper surface of the silicon substrate; the surface of the convex part on the upper surface of the silicon substrate is covered with an insulating layer; gallium nitride microwires are epitaxially grown on two inner side walls of the groove respectively, the extending direction of the gallium nitride microwires is the same as that of the groove, and the gallium nitride microwires form a parallel microwire array; the electrode is arranged on the upper surface of the silicon substrate, and the methyl amino lead iodide layer is coated on the upper surface of the silicon substrate to cover the electrode and the gallium nitride microwire so as to form a double heterojunction. The photoelectric detector has the advantages of low dark current, high response speed, high on/off current ratio, long detection range, good comprehensive performance, simple device structure and easy manufacture.

Description

Gallium nitride micron line array photoelectric detector

Technical Field

The utility model relates to a photoelectric detector technical field especially relates to a gallium nitride micron line array photoelectric detector.

Background

The photodetector operates by converting an optical signal into an electrical signal. Photodetectors are an important component in the field of optoelectronic information technology and have found widespread use in military, medical and life. For example: spacecraft, missile launching, fire detection, video imaging, and the like. Gallium nitride (GaN), a member of wide bandgap semiconductors, is considered to be an ideal material for a detector due to its wide bandgap (bandgap width 3.4eV), low dielectric constant, high temperature resistance, corrosion resistance, radiation resistance, and other properties. With the continuous development and progress of science, materials are continuously developed to the aspects of low dimension and small size. In one-dimensional nanostructures, micro/nanowires have better crystal quality and larger bulk surface area than bulk materials. Thus, many gallium nitride micro-nanowire structured photodetectors have emerged.

Gallium nitride photodetectors, due to their different operating principles, can be classified into photoconductive and photovoltaic types. The photovoltaic type can be divided into a schottky type and a homo/hetero junction type. The photoconductive type detector has a high gain but a large dark current, and the schottky type detector has a fast response speed but is greatly affected by a potential barrier. Thus, the heterojunction type is the best choice for achieving both a fast response speed and a low dark current. Due to the rapid development of perovskite materials in recent years, perovskite materials have good associativity and good material characteristics, and are a preferred choice as another material for heterojunction. Organic-inorganic hybrid perovskites have better stability, longer diffusion lengths and tunable bandgaps than pure organic or pure inorganic perovskites. Typically, methylaminolead iodide (CH3NH3PbI3) has a low energy gap (1.53eV) and a high absorption coefficient in the visible and near infrared regions, so that the use of CH3NH3PbI3 with n-type GaN as a uv-vis-nir photodetector is a desirable choice.

Some research on CH3NH3PbI3/GaN photodetectors is now being conducted by some teams and individuals at home and abroad, but most of them are GaN thin films combined with CH3NH3PbI3, and these photodetectors still have the following drawbacks: large dark current, low response speed and complex preparation; the comprehensive performance of the composite material needs to be further improved.

SUMMERY OF THE UTILITY MODEL

In order to overcome the defects of the prior art, one of the purposes of the utility model is to provide a gallium nitride micron line array photoelectric detector, the dark current of the photoelectric detector is low, the response speed is fast, the on/off current ratio is high, the detection range is long, the comprehensive performance is good, and the device structure is simple and easy to manufacture.

The utility model discloses an one of the purpose adopts following technical scheme to realize:

a gallium nitride microwire array photodetector, comprising: a silicon substrate, a methyl amino lead iodide layer and an electrode; a plurality of grooves which are arranged in parallel are formed on the upper surface of the silicon substrate; the surface of the convex part on the upper surface of the silicon substrate is covered with an insulating layer; gallium nitride microwires are epitaxially grown on two inner side walls of the groove respectively, the extending direction of the gallium nitride microwires is the same as that of the groove, and the gallium nitride microwires form a parallel microwire array; the electrode is arranged on the upper surface of the silicon substrate, and the methyl amino lead iodide layer is coated on the upper surface of the silicon substrate to cover the electrode and the gallium nitride microwire so as to form a double heterojunction.

Further, an aluminum nitride buffer layer is arranged between the gallium nitride microwire and the inner side wall of the groove.

Further, the thickness of the aluminum nitride buffer layer is 30 to 300 nm.

Further, the width of the groove is 8 to 12 μm, and the depth of the groove is 2.5 to 4 μm.

Further, the thickness of the methyl amino lead iodide layer is 200-400 nm.

Compared with the prior art, the beneficial effects of the utility model reside in that:

the photoelectric detector adopts a mode of growing the micron line in the groove, the micron line growing in the groove can greatly utilize the limited area of the substrate, the body surface area ratio is larger, the defects caused by lattice mismatch and thermal mismatch are greatly reduced, and the photoelectric detector has high crystal quality. Meanwhile, the contact area of the heterojunction is increased, so that the heterojunction has a large space charge region, photogenerated carriers are effectively separated, the recombination of the photogenerated carriers is effectively inhibited, and the response speed of the detector is improved. The photoelectric detector has the advantages of low dark current, high response speed, high on/off current ratio, long detection range, good comprehensive performance, simple device structure and easy manufacture.

Drawings

Fig. 1 is a schematic structural diagram of a gallium nitride microwire array photodetector provided by the present invention;

fig. 2 is a schematic structural view of a substrate of a gallium nitride microwire array photodetector provided by the present invention when no gallium nitride microwire is grown;

fig. 3 is a schematic structural view of a substrate with gan microwires epitaxially grown on the gan microwire array photodetector according to the present invention;

FIG. 4 is a schematic cross-sectional view of the substrate of FIG. 3;

FIG. 5 is a schematic cross-sectional view of the photodetector of FIG. 1 taken at the electrode location;

FIG. 6 is a schematic cross-sectional view of the photodetector of FIG. 1 taken at a non-electrode location, illustrating the double heterojunction structure formed by the photodetector;

FIG. 7 is a schematic cross-sectional view of the photodetector of FIG. 1 taken along the direction of extension of the groove at the location of the groove sidewalls;

fig. 8 is an I-V diagram of a gallium nitride microwire array photodetector illuminated by light of 325nm different optical powers;

FIG. 9 shows the I-T (part) of a GaN microwire array photodetector irradiated by 5V applied voltage, 325nm, 7.5mw/cm2 light;

fig. 10 is an I-V diagram of a gallium nitride microwire array photodetector illuminated by 532nm light with different optical powers;

FIG. 11 shows the I-T (part) of a GaN microwire array photodetector irradiated by 5V applied voltage, 532nm, 27.4mw/cm2 light;

fig. 12 is an I-V diagram of a gallium nitride microwire array photodetector illuminated by light of 750nm different optical powers according to the present invention;

fig. 13 shows the I-T (part) of a gan microwire array photodetector irradiated by 5V applied voltage, 750nm, 0.3mw/cm2 light.

In the figure: 10. a silicon substrate; 101. a groove; 102. an insulating layer; 20. a methylaminolead iodide layer; 30. an electrode; 40. a gallium nitride microwire; 50. an aluminum nitride buffer layer.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that the embodiments or technical features described below can be arbitrarily combined to form a new embodiment without conflict.

Referring to fig. 1 to 7, a gan microwire array photodetector includes: a silicon substrate 10, a methylaminolead iodide layer 20, and an electrode 30; the silicon substrate 10 is a high-resistance silicon wafer (the resistivity is more than 10)⁵Omega cm), the crystal orientation of the silicon chip is<100>(ii) a A plurality of silicon substrates 10 are formed on the upper surface thereofGrooves 101 arranged in parallel; the surface of the convex part on the upper surface of the silicon substrate 10 is covered with an insulating layer 102; the insulating layer 102 has a resistivity greater than 10¹⁶Omega cm; the insulating layer 102 is made of silicon dioxide; the thickness of the insulating layer 102 is preferably 300-500 nm; gallium nitride microwires 40 are epitaxially grown on two inner side walls of the groove 101 respectively, the extending direction of the gallium nitride microwires 40 is the same as that of the groove 101, and the gallium nitride microwires 40 form a parallel microwire array; the electrode 30 is a metal electrode, the electrode 30 is disposed on the upper surface of the silicon substrate 10, i.e., above the gallium nitride microwire array, and the methylaminolead iodide layer 20 is coated on the upper surface of the silicon substrate 10 to cover the electrode 30 and the gallium nitride microwire 40 to form a double heterojunction, i.e., the methylaminolead iodide layer 20 and the gallium nitride microwire array form a double heterojunction.

According to the photoelectric detector, the groove 101 is etched on the substrate, the micron line grows in the groove 101, the limited area of the substrate can be greatly utilized in the mode of growing the micron line in the groove 101, the body surface area ratio is enabled to be larger, the defects of a film-shaped structure caused by lattice mismatch and thermal mismatch due to the fact that layers are stacked are greatly reduced due to the fact that the growth of the limited area in the groove 101, and the photoelectric detector has high crystal quality. Meanwhile, the contact area of the heterojunction is increased, so that the heterojunction has a large space charge region, photogenerated carriers are effectively separated, the recombination of the photogenerated carriers is effectively inhibited, and the response speed of the detector is improved. The photoelectric detector has the advantages of low dark current, high response speed, high on/off current ratio, long detection range, good comprehensive performance, simple device structure and easy manufacture.

The working process of the photoelectric detector is as follows: absorbing light radiation by the methylaminolead iodide layer 20 to generate photogenerated carriers; the electrons and the holes in the space charge area formed between the methyl amino lead iodide and the gallium nitride micron line array are rapidly separated; holes remain in the methylaminolead iodide layer 20 and electrons move to the gallium nitride microwire 40; and eventually collected at the metal electrode 30.

The number of the electrodes is plural, and the interval between the electrodes is 5 to 20 μm.

In particular, the cross-section of the gallium nitride microwire 40 is triangular; one side of the triangle is in contact with the inner side wall of the groove 101; the growth height of the gallium nitride micro-wire 40 is preferably 3.7-4.2 μm, and when the growth height is between 3.7-4.2 μm, the gallium nitride micro-wire 40 grows in a shape of a triangle in cross section. If the growth height is too small, the cross section of the finally grown micron line is in a trapezoid shape, so that the defect is larger; if the height is too large, the two micron lines can touch together after growing, so that the top end is broken, and the leakage current is too large; when growing the gallium nitride microwires 40, the distance between two gallium nitride microwires 40 is set to be 50-200 nm, preferably 80 nm. When the growth is performed, if the two gan microwires 40 are too close to each other, the two gan microwires are overlapped to cause a fusing phenomenon, and therefore, the interval between the two gan microwires 40 cannot be too small; and too much will not allow the tips of the two growing microwires to touch together, resulting in too much leakage current. When the interval between the two gallium nitride microwires 40 is 80nm, the cross section of the grown microwire is triangular, and the tips of the microwires can touch each other but do not overlap, so that the fusing phenomenon does not occur.

As a preferred embodiment, an aluminum nitride buffer layer 50 is disposed between the gallium nitride microwire 40 and the inner sidewall of the groove 101, and the thickness of the aluminum nitride buffer layer 50 is 30 to 300 nm. By additionally arranging the aluminum nitride buffer layer 50, gallium nitride with better quality can be grown when the gallium nitride is grown; in addition, the aluminum nitride buffer layer 50 also serves as an insulator to prevent current from flowing out of the silicon. The aluminum nitride buffer layer 50 is set to a thickness of 30 to 300nm, and if the aluminum nitride buffer layer 50 is less than 30, it does not perform an insulating function, and if it is more than 300, a piece of aluminum nitride is formed inside the groove, including on the insulating layer 102, so that gallium nitride may grow to extend into the insulating layer 102, resulting in an increase in dark current.

In a preferred embodiment, the grooves 101 are preferably inverted trapezoidal grooves, i.e. the cross section of each groove is inverted trapezoidal, the width of the upper end of each groove 101 is 8 to 12 μm, the depth of each groove 101 is 2.5 to 4 μm, and the distance between every two grooves 101 is 10 μm. The groove 101 has the function of limiting the growth area and the shape of the microwire, the inverted trapezoidal groove enables the microwire to better grow into the microwire with the cross section in a triangular shape, the top ends of two gallium nitride microwires grown on the two inner side walls of the groove can be in mutual contact but are not overlapped, the problem that a large number of defects are caused due to large-area lattice mismatch caused by overlapping between films in a thin film structure is avoided, and the crystal quality is improved.

As a preferred embodiment, the thickness of the methylaminolead iodide layer 20 is preferably 200 to 400nm, and when the thickness of the methylaminolead iodide layer 20 is less than 200, the light absorption efficiency is not high, and the response efficiency is low; whereas a value higher than 400 prevents the transmission of photogenerated carriers into the gallium nitride microwire 40, hindering the transmission of carriers.

Referring to fig. 8 to 13, the current (dark current) of the photo detector provided by the present invention is 10 under the condition of no illumination under the external voltage of 5V^-10A, and different currents (photocurrents) are generated under the irradiation of light with different intensities at different wavelengths of 325nm, 532nm and 750nm respectively. At 325nm, 7.5mw/cm²Under the light irradiation, the current is increased by 2240 times; at 532nm, 27.4mw/cm²Under irradiation, the photocurrent is increased by 98 times; at 750nm, 0.3mw/cm²Under the light irradiation, the current is increased by 23 times. Under the applied voltage of 5V, 325nm and 7.5mw/cm²Under the light irradiation, when the light source is removed, the falling time of the photocurrent is 1.51 ms; at an applied voltage of 5V, 532nm, 27.4mw/cm²Under irradiation, when the light source is removed, the falling time of the photocurrent is 1.58 ms; at an applied voltage of 5V, 750nm and 0.3mw/cm²Under light irradiation, the fall time of the photocurrent when the light source was removed was 1.64 ms. When the illumination is re-supplied, the rise time of the photocurrent is 6.68ms, 1.17ms, and 1.64ms, respectively. These data illustrate the feasibility of the photodetector of the present invention, which has a long detection range. (Note: rise time means the time required for the dark current to rise to 90% of the steady current when the light is illuminated, and fall time means the light current when the light is removedThe time required for the reduction to 10% of the original stability. MW/cm²The optical power density is shown, indicating the intensity of the illumination radiation received per square centimeter, with greater optical power density indicating greater illumination. )

Due to lattice mismatch and thermal mismatch of the film material in the growth process, a large number of defects and dislocations are generated in the epitaxial film, and the performance of the device is reduced; and the utility model discloses the micron line of preparation has overcome the above-mentioned problem that thin film material exists, can obtain the micron line array of high crystal quality, improves the device performance.

In addition, the utility model also provides a preparation method of gallium nitride micron line array photoelectric detector, including following step:

etching a plurality of grooves which are arranged at equal intervals on the upper surface of the silicon substrate covered with the insulating layer;

epitaxially growing gallium nitride microwires on two inner side walls of the groove by a metal organic chemical vapor deposition method to form a microwire array, wherein the extending direction of the gallium nitride microwires is the same as that of the groove;

after growing the gallium nitride microwire, depositing an electrode on the upper surface of the silicon substrate;

after the electrode is deposited, a methylaminolead iodide layer is coated on the upper surface of the silicon substrate to cover the electrode and the gallium nitride microwire to form a double heterojunction.

As a preferred embodiment, the method further comprises the following steps before growing the gallium nitride microwire: epitaxially growing an aluminum nitride buffer layer on the inner side wall of the groove by a metal organic chemical vapor deposition method; and epitaxially growing the gallium nitride microwire on the aluminum nitride buffer layer.

As a preferred embodiment, the etching a plurality of grooves arranged at equal intervals on the upper surface of the silicon substrate covered with the insulating layer specifically includes:

preparing an insulating material on the front surface of a clean silicon substrate to form an insulating layer, wherein the substrate is a 2-inch intrinsic silicon wafer, and the resistivity of the silicon wafer substrate is more than 10⁵Omega cm; forming a layer on the surface of the silicon wafer by a thermal reduction methodA 300nm silicon dioxide insulating layer;

spin-coating photoresist on the surface of the insulating layer, and exposing the surface of the insulating layer to periodically arranged strip-shaped epitaxial patterns through pre-baking, exposure, post-baking and development; the thickness of the photoresist is 2 μm; wherein the width of each stripe interval is 10 μm;

selectively etching the upper surface of the silicon substrate according to the strip-shaped epitaxial pattern, and then carrying out photoresist removing treatment on the silicon substrate; the selective etching utilizes a buffered etching solution (BOE) to etch the silicon dioxide insulating layer without the protection of the photoresist, a silicon substrate with the thickness of 10 microns and a silicon dioxide layer with the protection of the photoresist with the thickness of 10 microns are formed to alternately appear, then acetone and isopropanol are utilized to remove the photoresist, and deionized water is used for cleaning.

And according to the required groove depth, after removing the glue, carrying out timing wet etching on the part of the silicon substrate which is not covered with the insulating layer to form a plurality of grooves which are arranged in parallel at equal intervals. The solution is strong alkali solution (mixed solution of potassium hydroxide and isopropanol), the obtained substrate is cleaned by deionized water, and water on the surface of the substrate is dried by a nitrogen gun.

As a preferred embodiment, the depositing an electrode on the upper surface of the silicon substrate specifically includes: au metal is vapor-deposited or sputtered on the surface of the silicon substrate on which the gallium nitride microwire is provided by a thermal vapor deposition or ion sputtering method to form a metal electrode. The method specifically comprises the following steps: photoetching electrodes by utilizing a photoetching process, wherein the distance between the metal electrodes is 20 mu m, and performing thermal evaporation on a substrate obtained after the photoetching electrodes to evaporate Au metal; and (4) carrying out processes such as photoresist removal and cleaning on the evaporated epitaxial structure.

As a preferred embodiment, the coating of the methylaminolead iodide layer on the upper surface of the silicon substrate is specifically: and spin-coating a methyl amino lead iodide layer on the upper surface of the silicon substrate in a glove box. The method specifically comprises the following steps: and transferring the metal evaporated gallium nitride nanowire array into a glove box, and spin-coating the prepared methyl amino lead iodide solution in the glove box on the gallium nitride nanowire array and the metal electrode by using a spin coater. The step of spin coating the methyl amino lead iodide comprises the following steps: setting the rotating speed of a spin coater to 700r/3s and 4000r/25 s; using a pipette to suck 60 mul of the solution on the GaN micron line array, and dripping 100 mul of chlorobenzene at 18 s; the hot plate is set at 45 deg.C, annealed for 30min, and then at 105 deg.C, annealed for 5 min. The thickness of the obtained methyl amino lead iodide layer is 200-400 nm.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention cannot be limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are all within the protection scope of the present invention.

Claims

1. A gallium nitride microwire array photodetector, comprising: a silicon substrate, a methyl amino lead iodide layer and an electrode; a plurality of grooves which are arranged in parallel are formed on the upper surface of the silicon substrate; the surface of the convex part on the upper surface of the silicon substrate is covered with an insulating layer; gallium nitride microwires are epitaxially grown on two inner side walls of the groove respectively, the extending direction of the gallium nitride microwires is the same as that of the groove, and the gallium nitride microwires form a parallel microwire array; the electrode is arranged on the upper surface of the silicon substrate, and the methyl amino lead iodide layer is coated on the upper surface of the silicon substrate to cover the electrode and the gallium nitride microwire so as to form a double heterojunction.

2. The gan microwire array photodetector of claim 1, wherein an aluminum nitride buffer layer is disposed between said gan microwire and said inner sidewall of said trench.

3. The gallium nitride microwire array photodetector of claim 2, wherein said aluminum nitride buffer layer has a thickness of 30 to 300 nm.

4. The gallium nitride microwire array photodetector of claim 1, wherein said grooves have a width of 8 to 12 μm and a depth of 2.5 to 4 μm.

5. The gallium nitride microwire array photodetector of claim 1, wherein said layer of methyl amino lead iodide has a thickness of 200 to 400 nm.