CN114784123A - Nonpolar a-surface GaN-based ultraviolet photoelectric detector and preparation method thereof - Google Patents
Nonpolar a-surface GaN-based ultraviolet photoelectric detector and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a nonpolar a-surface GaN-based ultraviolet photoelectric detector and a preparation method thereof, wherein the ultraviolet photoelectric detector comprises an ultraviolet photoelectric detector epitaxial wafer and Si deposited on the ultraviolet photoelectric detector epitaxial wafer3N4The Schottky interdigital electrode of the asymmetric MSM structure; the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-surface AlN buffer layer and a nonpolar a-surface Al with gradually changed components, which sequentially grow on a r-surface sapphire substratexGa1‑xThe GaN substrate comprises an N buffer layer and a nonpolar a-plane GaN epitaxial layer, wherein x is 0.2-0.8; si3N4The passivation layer is arranged on the nonpolar a-surface GaN epitaxial layer; schottky inter-digital electrode penetration Si3N4And the passivation layer is in direct contact with the nonpolar a-surface GaN epitaxial layer on the ultraviolet photoelectric detector epitaxial wafer. The invention realizes high performanceThe nonpolar a-plane GaN ultraviolet photoelectric detector reduces the dark current of the device and increases the stability.
Description
Technical Field
The invention relates to the technical field of ultraviolet photoelectric detectors, in particular to a nonpolar a-surface GaN-based ultraviolet photoelectric detector and a preparation method thereof.
Background
The ultraviolet photoelectric detector is a photoelectric component which plays an important role in the fields of missile guidance, space communication, environment monitoring, biochemical ultraviolet detection and the like. The third generation of wide band gap semiconductor material GaN has the characteristics of large forbidden band width, high electron migration rate, good thermal stability and strong radiation resistance, is very suitable for manufacturing electronic devices with high frequency, high power and high integration, and is well applied to the field of ultraviolet photoelectric detectors.
However, most of the materials of the current commercial GaN-based ultraviolet photodetectors use the c plane ((0001) plane) as an epitaxial plane, and such materials have serious spontaneous polarization and piezoelectric polarization effects, generate a strong built-in electric field, and form a Quantum-confined Starker Effect (QCSE), so that the spatial distribution of electron and hole wave functions is separated, causing band bending, reducing the external Quantum efficiency, increasing the dark current of the device, and making the detection performance unstable, thereby seriously hindering the improvement of the performance of the ultraviolet photodetector. In addition, the p-n junction type or p-i-n type structure widely adopted at present is restricted by two aspects, on one hand, the GaN has high n-type background carrier concentration in the GaN due to unintentional doping, and most Mg can not be activated due to passivation in the process of doping Mg into GaN, so that p-type doping is difficult, and a p-type material with high hole concentration is difficult to prepare; on the other hand, the p-i-n type ultraviolet photoelectric detector has a complex structure, a complex preparation process, and large time cost and process cost, and is not beneficial to large-scale production and manufacturing.
Therefore, the research can avoid the spontaneous polarization of the nonpolar GaN material, and the development of a more superior device structure and a simple preparation method has pioneering and revolutionary significance and social value for the development of the ultraviolet photoelectric detector.
Disclosure of Invention
In order to solve the above-mentioned existing problemsThe invention provides a nonpolar a-surface GaN-based ultraviolet photoelectric detector and a preparation method thereof3N4And the passivation layer is in direct contact with the nonpolar a-plane GaN epitaxial layer, so that the ultraviolet photoelectric detector has high performance of low dark current and high stability.
The invention aims to provide a nonpolar a-plane GaN-based ultraviolet photoelectric detector.
The invention provides a preparation method of a nonpolar a-plane GaN-based ultraviolet photoelectric detector.
The invention also aims to provide another preparation method based on the nonpolar a-side GaN-based ultraviolet photoelectric detector.
The first purpose of the invention can be achieved by adopting the following technical scheme:
comprises an ultraviolet photoelectric detector epitaxial wafer and Si deposited on the ultraviolet photoelectric detector epitaxial wafer3N4Passivation layer, and the schottky interdigital electrode of asymmetric MSM structure, wherein:
the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-surface AlN buffer layer and a nonpolar a-surface Al with gradually changed components, which sequentially grow on a r-surface sapphire substratexGa1-xThe GaN substrate comprises an N buffer layer and a nonpolar a-surface GaN epitaxial layer, wherein x is 0.2-0.8;
said Si3N4The passivation layer is arranged on the nonpolar a-surface GaN epitaxial layer;
the Schottky interdigital electrode penetrates through the Si3N4And the passivation layer is in direct contact with the nonpolar a-surface GaN epitaxial layer on the ultraviolet photoelectric detector epitaxial wafer.
Further, the Schottky interdigital electrode is made of vapor deposition electrode metal, the electrode metal is sequentially stacked from bottom to top through Ni/Au, and the total electrode thickness is 200-300 nm.
Furthermore, the width of the large interdigital electrode and the width of the small interdigital electrode in the Schottky interdigital electrode are 5-15 μm, the distance between the large interdigital electrode and the small interdigital electrode is 5-10 μm, and the width of the large interdigital electrode is larger than that of the small interdigital electrode.
Furthermore, the r-plane sapphire substrate takes a 10-12 plane offset 1-100 direction 0.1 DEG as an epitaxial plane, and the nonpolar a-plane AlN buffer layer and the nonpolar a-plane Al are arranged on the epitaxial planexGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are both arranged such that the 0001 plane is parallel to the-1011 plane of the r-plane sapphire, and the a plane is used as an epitaxial plane.
Further, the thickness of the nonpolar a-surface AlN buffer layer is 120-200 nm, and the nonpolar a-surface Al buffer layer is made of AlxGa1-xThe thickness of the N buffer layer is 450-600 nm, the thickness of the a-surface GaN epitaxial layer is 3-4 mu m, and the thickness of the Si buffer layer is3N4The thickness of the passivation layer is 120-160 nm.
Further, the thickness of the sapphire on the r surface is 400 μm.
The second purpose of the invention can be achieved by adopting the following technical scheme:
a preparation method of a nonpolar a-plane GaN-based ultraviolet photoelectric detector comprises the following steps:
sequentially growing a nonpolar a-surface AlN buffer layer and a nonpolar a-surface Al on an r-surface sapphire substratexGa1-xObtaining an ultraviolet photoelectric detector epitaxial wafer by using an N buffer layer and a nonpolar a-plane GaN epitaxial layer, and preprocessing the obtained ultraviolet photoelectric detector epitaxial wafer, wherein x is 0.2-0.8;
depositing Si on the surface of the pretreated ultraviolet photoelectric detector epitaxial wafer by adopting a plasma-assisted chemical vapor deposition method3N4A passivation layer;
to deposit Si3N4Coating positive photoresist on the surface of the ultraviolet photoelectric detector epitaxial wafer of the passivation layer, and forming an asymmetric interdigital electrode by using a mask plate to obtain an electrode channel pattern;
wet etching the ultraviolet photoelectric detector epitaxial wafer with the electrode channel pattern to etch off Si in the window area not covered by the photoresist3N4Passivating a layer to obtain an asymmetric Schottky electrode groove;
putting the etched ultraviolet photoelectric detector epitaxial wafer into an electron beam for evaporationIn the equipment, evaporating electrode metal to obtain a Schottky interdigital electrode with an asymmetric MSM structure, and annealing; wherein the Schottky inter-digital electrode penetrates the Si3N4The passivation layer is in direct contact with the nonpolar a-surface GaN epitaxial layer;
and processing and scribing the ultraviolet photoelectric detector epitaxial wafer of the obtained Schottky interdigital electrode, and separating out independent small devices to obtain the nonpolar a-surface GaN-based ultraviolet photoelectric detector.
Furthermore, the r-plane sapphire substrate takes 10-12 planes deviated from 1-100 directions by 0.1 degrees as epitaxial planes, and the nonpolar a-plane AlN buffer layer and the nonpolar a-plane Al are arranged on the substratexGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are both arranged such that the 0001 plane is parallel to the-1011 plane of the r-plane sapphire, and the a plane is used as an epitaxial plane.
The third purpose of the invention can be achieved by adopting the following technical scheme:
a preparation method of a nonpolar a-plane GaN-based ultraviolet photoelectric detector comprises the following steps:
sequentially growing a nonpolar a-surface AlN buffer layer and nonpolar a-surface Al on a r-surface sapphire substratexGa1-xObtaining an ultraviolet photoelectric detector epitaxial wafer by using an N buffer layer and a nonpolar a-plane GaN epitaxial layer, and preprocessing the obtained ultraviolet photoelectric detector epitaxial wafer, wherein x is 0.2-0.8;
coating a positive photoresist on the surface of the pretreated ultraviolet photoelectric detector epitaxial wafer, and forming an asymmetric interdigital electrode by using a mask to obtain an electrode channel pattern;
placing the ultraviolet photoelectric detector epitaxial wafer with the electrode channel pattern into an electron beam evaporation device, evaporating electrode metal to obtain a Schottky interdigital electrode with an asymmetric structure, and annealing;
coating negative photoresist on the surface of an epitaxial wafer of the ultraviolet photoelectric detector with the Schottky interdigital electrode, and forming an asymmetric interdigital electrode by using a mask plate to obtain an electrode isolation pattern;
placing the ultraviolet photoelectric detector epitaxial wafer with the prepared electrode isolation pattern in plasma-assisted chemical vapor deposition equipment to deposit Si3N4Passivation ofA layer;
removing deposited Si3N4And (4) carrying out photoresist scribing on the ultraviolet photoelectric detector epitaxial wafer of the passivation layer, and separating out an independent small device to obtain the nonpolar a-surface GaN-based ultraviolet photoelectric detector.
Furthermore, the r-plane sapphire substrate takes 10-12 planes deviated from 1-100 directions by 0.1 degrees as epitaxial planes, and the nonpolar a-plane AlN buffer layer and the nonpolar a-plane Al are arranged on the substratexGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are both arranged such that the 0001 plane is parallel to the-1011 plane of the r-plane sapphire, and the a plane is used as an epitaxial plane.
Compared with the prior art, the invention has the following beneficial effects:
1. in addition, the nonpolar a-plane AlN and the nonpolar a-plane AlxGa1-xN with gradually changed components are used as buffer layers to be slowly transited to the nonpolar a-plane GaN, so that the lattice mismatch degree between the nonpolar a-plane GaN and the substrate can be effectively reduced, the stress is released in the epitaxial growth process, the upward extension of defects is reduced, and the electric leakage phenomenon caused by overlarge defect density of the epitaxial film is avoided.
2. According to the invention, the nonpolar a-plane GaN is used as a light absorption material, on one hand, the material has no polarized electric field along the growth direction, so that the separation of electron and hole wave functions on the space can be effectively avoided, the external quantum efficiency is improved, and the reduction of the starting voltage of a device is facilitated; in addition, due to the optical anisotropy of the material, the electric dipole at the top of the valence band can absorb polarized light vertical to the surface, and has unique advantages in polarization detection.
3. The ultraviolet photoelectric detector adopts a Schottky contact asymmetric metal-semiconductor-metal (MSM) structure, has simple preparation process, does not need to involve p-type doping, and has the advantages of high response speed, low dark current, high light responsiveness and stable performance in performance. In addition, compared with a symmetrical structure, the Schottky interdigital electrode with the asymmetrical structure has the advantages that the current density of the electrode which is in small-area contact is higher than that of the electrode which is in large-area contact under the condition of external bias voltage, so that the electrode with the smaller area obtains a larger electric field, a depletion layer expands towards the electrode with the larger area, the penetration voltage is reduced, and the further reduction of dark current is facilitated.
4. The Schottky metal electrode adopted by the invention is Ni/Au. The traditional single Au electrode is poor in adhesion and easy to fall off, so that the failure rate of the ultraviolet photoelectric detector is high, and Ni is used as an adhesive, so that the adhesion between Au and non-polar a-surface GaN is increased, and the problem of electrode falling off is avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic cross-sectional view of a non-polar a-plane GaN-based ultraviolet photodetector structure according to an embodiment of the present invention.
Fig. 2 is a schematic top view of an asymmetric schottky interdigital electrode structure of a nonpolar a-plane GaN-based ultraviolet photodetector according to an embodiment of the present invention.
FIG. 3 is a graph of dark current of a nonpolar a-plane GaN-based UV photodetector according to an embodiment of the invention as a function of applied bias.
Fig. 4 is a graph showing the spectral response of the nonpolar a-plane GaN-based uv photodetector according to the embodiment of the present invention.
In FIG. 1:
1-r surface sapphire substrate, 2-nonpolar a surface AlN buffer layer, 3-component gradient nonpolar a surface AlxGa1-xN buffer layer, 4-nonpolar a-plane GaN epitaxial layer, 5-Si3N4Passivation layer, 6-asymmetric schottky interdigital electrode.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention. It should be understood that the description of the specific embodiments is intended to be illustrative only and is not intended to be limiting.
Example 1:
the embodiment provides a preparation method of a nonpolar a-surface GaN-based ultraviolet photoelectric detector, which specifically comprises the following steps:
(1) as shown in figure 1, a metallorganic chemical vapor deposition technology is adopted to grow an ultraviolet photoelectric detector epitaxial wafer on a r-plane sapphire substrate 1, and the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-plane AlN buffer layer 2 and a nonpolar a-plane Al with gradually changed componentsxGa1-xThe N buffer layer 3 and the nonpolar a-plane GaN epitaxial layer 4, wherein x is 0.2 to 0.8.
(2) And (2) cleaning the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (1), soaking the ultraviolet photoelectric detector epitaxial wafer by sequentially adopting acetone and absolute ethyl alcohol, ultrasonically cleaning the ultraviolet photoelectric detector epitaxial wafer for 3min, washing the ultraviolet photoelectric detector epitaxial wafer by adopting deionized water after cleaning, and drying the ultraviolet photoelectric detector epitaxial wafer in hot high-purity nitrogen.
(3) Depositing a layer of Si on the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (2) by adopting a plasma-assisted chemical vapor deposition method3N4A passivation layer 5; after deposition, the substrate is rinsed with deionized water and blown dry with hot high purity nitrogen.
(4) And (4) preparing an electrode channel pattern of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (3): dripping a proper amount of positive photoresist on the surface of the ultraviolet photoelectric detector epitaxial wafer, placing the ultraviolet photoelectric detector epitaxial wafer in a spin coater to enable the thickness of the photoresist on the surface to be uniformly covered, wherein the thickness is 0.2 mu m, and then baking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at the temperature of 95 ℃; then placing the interdigital electrode into a photoetching machine, and forming an asymmetric interdigital electrode by adopting a mask plate, wherein the widths of the large electrode and the small electrode are both specified values, the distance between the interdigital electrodes is 5-10 mu m, and the number of electrode pairs is a specified value; then, exposure is carried out for 15 s; and finally, developing the exposed ultraviolet photoelectric detector epitaxial wafer in a developing solution for 60s, cleaning the ultraviolet photoelectric detector epitaxial wafer by using deionized water, drying the ultraviolet photoelectric detector epitaxial wafer by using hot high-purity nitrogen, and then placing the ultraviolet photoelectric detector epitaxial wafer on a hot plate furnace for post-baking. In this embodiment, the width of the large electrode is larger than that of the small electrode, and the widths of the large electrode and the small electrode are 5-15 μm.
(5) Carrying out wet etching on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (4), and carrying out wet etching on Si which is not covered by the photoresist3N4Etching the passivation layer to obtain a Schottky electrode groove; then rinsed with deionized water and blown dry with hot high purity nitrogen.
(6) And (4) placing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (5) in an electron beam evaporation device for evaporating an electrode, vacuumizing the interior of a cavity, evaporating a metal layer to obtain a Schottky interdigital electrode 6 with an asymmetric MSM structure, and finally annealing at 900 ℃, wherein the asymmetric MSM structure is formed by back-to-back Schottky interdigital electrodes with asymmetric area.
(7) And (5) carrying out photoresist removal treatment on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (6): after the temperature is reduced to room temperature, the mixture is sequentially placed in acetone and absolute ethyl alcohol for ultrasonic treatment for 3min, then is washed by deionized water, and is dried by hot high-purity nitrogen.
(8) And (4) scribing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (7), and separating out an independent small device to obtain the nonpolar a-plane GaN asymmetric MSM structure ultraviolet photoelectric detector, as shown in fig. 1 and fig. 2.
Wherein:
the r-plane sapphire substrate in the step (1) takes a (10-12) plane deviation (1-100) direction of 0.1 degree as an epitaxial plane, and the crystal epitaxial orientation relation is as follows: the nonpolar a-surface AlN buffer layer and the nonpolar a-surface AlxGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are respectively provided with a (0001) plane parallel to a (-1011) plane of r-plane sapphire, and an a plane (11-20) plane is used as an epitaxial plane;
performing wet etching in the step (5), wherein the soaking time is 50-100 min;
the metal electrodes in the step (6) are sequentially stacked from bottom to top through Ni/Au, and the total thickness of the electrodes is 200-300 nm; the back partThe fire time is 30-80 min; the Schottky interdigital electrode penetrates through Si3N4The passivation layer is directly contacted with the nonpolar a-surface GaN epitaxial layer, and the Schottky interdigital electrode is directly contacted with the nonpolar a-surface GaN epitaxial layer, so that the reflection of incident light can be reduced, and the light response performance can be improved.
Because the schottky interdigital electrode adopts an asymmetric metal-semiconductor-metal (MSM) structure, the preparation process is simple, p-type doping is not required, and the schottky interdigital electrode has the advantages of high response speed, low dark current, high light responsivity and stable performance in performance, so that the ultraviolet photoelectric detector prepared by the embodiment has high performance of low dark current and high stability.
Example 2:
the embodiment provides a preparation method of a nonpolar a-plane GaN asymmetric MSM type ultraviolet photodetector, which specifically comprises the following steps:
(1) as shown in figure 1, a metallorganic chemical vapor deposition technology is adopted to grow an ultraviolet photoelectric detector epitaxial wafer on a r-plane sapphire substrate 1, and the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-plane AlN buffer layer 2 and a nonpolar a-plane Al with gradually changed componentsxGa1-xAn N buffer layer 3 and a nonpolar a-plane GaN epitaxial layer 4, wherein:
the nonpolar a-surface AlN buffer layer 2 grows on the r-surface sapphire substrate 1, and the thickness is 120 nm;
non-polar a-side Al with gradually changed componentsxGa1-xThe N buffer layer 3 grows on the nonpolar a-surface AlN buffer layer 2, and the thickness is 450 nm;
the non-polar a-surface GaN epitaxial layer grows on the non-polar a-surface Al with gradually changed componentsxGa1-xOn the N buffer layer 3, the thickness was 3 μm.
(2) And (2) cleaning the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (1), soaking the ultraviolet photoelectric detector epitaxial wafer by sequentially adopting acetone and absolute ethyl alcohol, ultrasonically cleaning the ultraviolet photoelectric detector epitaxial wafer for 3min, washing the ultraviolet photoelectric detector epitaxial wafer by adopting deionized water after cleaning, and drying the ultraviolet photoelectric detector epitaxial wafer in hot high-purity nitrogen.
(3) Depositing a layer of Si with the thickness of 120nm on the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (2) by adopting a plasma-assisted chemical vapor deposition method3N4A passivation layer 5, wherein the deposition temperature is 850 ℃; after the deposition is finished usingDeionized water rinse and blow dry with hot high purity nitrogen.
(4) Photoetching the ultraviolet photoelectric detector epitaxial wafer obtained in the step (3): dripping a proper amount of positive photoresist with the model number of RZJ304 on the surface of an epitaxial wafer of the ultraviolet photoelectric detector, placing the epitaxial wafer in a spin coater for processing, and spin-coating the photoresist for 30s at the rotating speed of 3600 r/min to ensure that the thickness of the photoresist on the surface is uniformly covered and is 0.2 mu m; then prebaking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at 95 ℃, then placing the ultraviolet photoelectric detector epitaxial wafer into a photoetching machine, and aligning by adopting a mask with asymmetric electrodes, wherein the detector parameters of the mask are that the width of a small electrode is 5 mu m, the width of a large electrode is 15 mu m, the distance between interdigital electrodes is 5 mu m, and the number of electrode pairs is 8; then, carrying out exposure for 15 s; then, the exposed ultraviolet photoelectric detector epitaxial wafer is placed in a positive developing solution to be soaked for 60s, wherein the model of the developing solution is RZX 3038; and cleaning the substrate with deionized water after the development is finished, drying the substrate with hot high-purity nitrogen, and then placing the substrate on a hot plate furnace for post-baking for 90 s.
(5) Carrying out wet etching on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (4) for 50min, and carrying out wet etching on Si which is not covered by the photoresist3N4Etching the passivation layer to obtain an electrode groove; then rinsed with deionized water and blown dry with hot high purity nitrogen.
(6) Placing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (5) in an electron beam evaporation device to evaporate metal electrodes, and keeping the vacuum degree in the cavity at 5 multiplied by 10-5Pa, firstly evaporating a Ni metal electrode with the thickness of 30nm at the evaporation rate of 0.1nm/s, then evaporating an Au metal electrode with the thickness of 170nm at the evaporation rate of 1nm/s, wherein the total electrode thickness is 200nm, annealing at 900 ℃ for 30s after evaporation is finished to obtain the asymmetric Schottky interdigital electrode 6, and finally annealing at 900 ℃ for 30 min.
(7) And (5) carrying out photoresist removal treatment on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (6): after the temperature is reduced to room temperature, the mixture is placed in acetone and absolute ethyl alcohol in sequence for ultrasonic treatment for 3min, then is washed by deionized water, and is dried by hot high-purity nitrogen.
(8) And (4) scribing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (7), and separating out an independent small device to obtain the nonpolar a-plane GaN asymmetric MSM structure ultraviolet photoelectric detector.
The structure of the nonpolar a-plane GaN-based uv photodetector manufactured in this example is shown in fig. 1 and 2.
The curve of the dark current varying with the applied bias obtained by connecting the small electrode of the nonpolar a-plane GaN-based ultraviolet photodetector to the anode and the large electrode to the cathode is shown in fig. 3. as can be seen from fig. 3, the absolute value of the dark current increases with the increase of the absolute value of the applied bias, and when a reverse bias is applied, the dark current is significantly lower than the applied forward bias, showing significant asymmetry. Under a bias of-5V, the dark current is only 1.46nA, which indicates that the ultraviolet photoelectric detector has very good low dark current performance under reverse bias.
The spectral response curve diagram of the nonpolar a-surface GaN-based ultraviolet photodetector is shown in FIG. 4, and it can be known from FIG. 4 that the responsivity rapidly decreases after reaching a peak value at 365nm, and a steep cut-off edge is presented, which indicates that the nonpolar a-surface GaN-based ultraviolet photodetector has a good "visible blind" characteristic, and reflects that the nonpolar a-surface GaN-based ultraviolet photodetector has a very sensitive detection capability on ultraviolet light.
Example 3:
the embodiment provides a preparation method of a nonpolar a-plane GaN asymmetric MSM type ultraviolet photodetector, which specifically comprises the following steps:
(1) as shown in figure 1, a metallorganic chemical vapor deposition technology is adopted to grow an ultraviolet photoelectric detector epitaxial wafer on a r-plane sapphire substrate 1, and the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-plane AlN buffer layer 2 and a nonpolar a-plane Al with gradually changed componentsxGa1-xAn N buffer layer 3 and a nonpolar a-plane GaN epitaxial layer 4, wherein:
the nonpolar a-plane AlN buffer layer 2 grows on the r-plane sapphire substrate, and the thickness is 200 nm;
non-polar a-plane Al with gradually changed compositionxGa1-xThe N buffer layer 3 grows on the nonpolar a-surface AlN buffer layer 2, and the thickness is 600 nm;
the nonpolar a-surface GaN epitaxial layer grows on the nonpolar a-surface Al with gradually changed componentsxGa1-xThe thickness of the N buffer layer 3 is 4 mu m;
(2) and (2) cleaning the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (1), soaking the ultraviolet photoelectric detector epitaxial wafer by using acetone and absolute ethyl alcohol in sequence, cleaning the surface for 3min by using ultrasonic waves, washing the surface by using deionized water after cleaning, and drying the surface in hot high-purity nitrogen.
(3) Depositing a layer of Si with the thickness of 160nm on the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (2) by adopting a plasma-assisted chemical vapor deposition method3N4A passivation layer 5, wherein the deposition temperature is 850 ℃; after deposition, the substrate is rinsed with deionized water and blown dry with hot high purity nitrogen.
(4) Photoetching the ultraviolet photoelectric detector epitaxial wafer obtained in the step (3): dripping a proper amount of positive photoresist with the model number of RZJ304 on the surface of the ultraviolet photoelectric detector epitaxial wafer, placing the ultraviolet photoelectric detector epitaxial wafer in a spin coater for processing, and spin-coating for 30s at the rotating speed of 3600 r/min to uniformly cover the photoresist on the surface with the thickness of 0.2 mu m; then prebaking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at 95 ℃, then placing the ultraviolet photoelectric detector epitaxial wafer into a photoetching machine, and aligning by adopting a mask with asymmetric electrodes, wherein the detector parameters of the mask are that the width of a small electrode is 5 mu m, the width of a large electrode is 15 mu m, the distance between interdigital electrodes is 10 mu m, and the number of electrode pairs is 8; then, exposure is carried out for 15 s; then, the exposed epitaxial wafer of the ultraviolet photoelectric detector is placed in positive developing solution to be soaked for 60s, wherein the model of the developing solution is RZX 3038; and cleaning with deionized water after the development is finished, blow-drying with hot high-purity nitrogen, and placing on a hot plate furnace for post-baking for 90 s.
(5) Carrying out wet etching on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (4) for 100min, and carrying out wet etching on Si not covered by the photoresist3N4Etching the passivation layer to obtain an electrode groove; then rinsed with deionized water and blown dry with hot high purity nitrogen.
(6) Placing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (5) in an electron beam evaporation device to evaporate metal electrodes, and keeping the vacuum degree in the cavity at 5 multiplied by 10-5Pa, evaporating Ni metal electrode with thickness of 30nm at evaporation rate of 0.1nm/s, and evaporating Au metal electrode with thickness of 270nm at evaporation rate of 1nm/s, wherein the total electrode thicknessThe temperature is 300nm, annealing is carried out for 30s at 900 ℃ after evaporation is finished, the asymmetric Schottky interdigital electrode 6 is obtained, and finally annealing is carried out for 80min at 900 ℃.
(7) And (4) carrying out photoresist removing treatment on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (6): after the temperature is reduced to room temperature, the mixture is placed in acetone and absolute ethyl alcohol in sequence for ultrasonic treatment for 3min, then is washed by deionized water, and is dried by hot high-purity nitrogen.
(8) And (4) scribing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (7), and separating out an independent small device to obtain the nonpolar a-plane GaN asymmetric MSM structure ultraviolet photoelectric detector.
In the embodiment of the invention, the nonpolar a-surface AlN buffer layer and the nonpolar a-surface Al with gradually changed componentsxGa1-xThe N buffer layer and the nonpolar a-surface GaN epitaxial layer have larger thicknesses, so that the defect density of the ultraviolet photoelectric detector epitaxial wafer can be effectively reduced; moreover, the interdigital distance is wider, the thickness of a passivation layer is larger, the responsivity of the detector is improved to a great extent, and the detector has good visible blind characteristics and very sensitive detection capability on ultraviolet light; while having very good low dark current performance under reverse bias.
Example 4:
the embodiment provides a preparation method of a nonpolar a-plane GaN asymmetric MSM structure ultraviolet photodetector, which specifically comprises the following steps:
(1) as shown in figure 1, a metallorganic chemical vapor deposition technology is adopted to grow an ultraviolet photoelectric detector epitaxial wafer on a r-plane sapphire substrate 1, wherein the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-plane AlN buffer layer 2 and a nonpolar a-plane Al with gradually changed componentsxGa1-xAn N buffer layer 3 and a nonpolar a-plane GaN epitaxial layer 4, wherein:
the nonpolar a-surface AlN buffer layer 2 grows on the r-surface sapphire substrate, and the thickness is 120 nm;
non-polar a-plane Al with gradually changed compositionxGa1-xThe N buffer layer 3 grows on the nonpolar a-surface AlN buffer layer 2, and the thickness is 450 nm;
the non-polar a-surface GaN epitaxial layer grows on the non-polar a-surface Al with gradually changed componentsxGa1-xOn the N buffer layer 3, the thickness was 3 μm.
(2) And (2) cleaning the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (1), soaking the ultraviolet photoelectric detector epitaxial wafer by sequentially adopting acetone and absolute ethyl alcohol, ultrasonically cleaning the ultraviolet photoelectric detector epitaxial wafer for 3min, washing the ultraviolet photoelectric detector epitaxial wafer by adopting deionized water after cleaning, and drying the ultraviolet photoelectric detector epitaxial wafer in hot high-purity nitrogen.
(3) Photoetching the ultraviolet photoelectric detector epitaxial wafer obtained in the step (2): dripping a proper amount of positive photoresist with the model number of RZJ304 on the surface of an epitaxial wafer of the ultraviolet photoelectric detector, placing the epitaxial wafer in a spin coater for processing, and spin-coating the photoresist for 30s at the rotating speed of 3600 r/min to ensure that the thickness of the photoresist on the surface is uniformly covered and is 0.2 mu m; then prebaking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at 95 ℃, then placing the ultraviolet photoelectric detector epitaxial wafer into a photoetching machine, and aligning by adopting a mask with asymmetric electrodes, wherein the detector parameters of the mask are that the width of a small electrode is 5 mu m, the width of a large electrode is 15 mu m, the distance between interdigital electrodes is 5 mu m, and the number of electrode pairs is 8; exposure was then carried out for 15 s.
(4) Soaking the exposed epitaxial wafer of the ultraviolet photoelectric detector in the step (3) in positive developing solution for 60s, wherein the model of the developing solution is RZX 3038; and cleaning the substrate with deionized water after the development is finished, drying the substrate with hot high-purity nitrogen, and then placing the substrate on a hot plate furnace for post-baking for 90 s.
(5) And (5) observing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (4) under a microscope, determining that the photoresist in the electrode area is completely removed, and only leaving the isolation pattern in the non-electrode area.
(6) Placing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (5) in an electron beam evaporation device for evaporating electrodes, and keeping the vacuum degree in a cavity at 5 multiplied by 10-5Pa, firstly evaporating a Ni metal electrode with the thickness of 30nm at the evaporation rate of 0.1nm/s, then evaporating an Au metal electrode with the thickness of 170nm at the evaporation rate of 1nm/s, wherein the total electrode thickness is 200nm, annealing at 900 ℃ for 30s after evaporation is finished to obtain the asymmetric Schottky interdigital electrode 6, and finally annealing at 900 ℃ for 30 min.
(7) And (4) carrying out photoresist removing treatment on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (6): after the temperature is reduced to room temperature, the mixture is placed in acetone and absolute ethyl alcohol in sequence for ultrasonic treatment for 3min, then is washed by deionized water, and is dried by hot high-purity nitrogen.
(8)Si3N4Preparing a passivation layer isolation pattern: photoetching the ultraviolet photoelectric detector epitaxial wafer obtained in the step (7): dripping a proper amount of negative photoresist (model number is RFJ-210) on the surface of the ultraviolet photoelectric detector epitaxial wafer, placing the ultraviolet photoelectric detector epitaxial wafer in a spin coater for processing, and spin-coating for 30s at the rotating speed of 3600 r/min to uniformly cover the thickness of the photoresist on the surface, wherein the thickness is 0.2 mu m; then prebaking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at 95 ℃, then placing the ultraviolet photoelectric detector epitaxial wafer in a photoetching machine, aligning by adopting a mask plate with an asymmetric electrode, and then exposing for 15 s; then, placing the exposed epitaxial wafer of the ultraviolet photoelectric detector in a developing solution to be soaked for 60s, wherein the model is RFX-2277; and cleaning with deionized water after the development is finished, blow-drying with hot high-purity nitrogen, and placing on a hot plate furnace for post-baking for 90 s.
(9) And (5) observing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (8) under a microscope, determining that the photoresist in the non-electrode area is completely removed, and only leaving the isolation pattern in the electrode area.
(10) Depositing a layer of Si with the thickness of 120nm on the surface of the obtained ultraviolet photoelectric detector epitaxial wafer by adopting a plasma-assisted chemical vapor deposition method3N4And the deposition temperature of the passivation layer 5 is 850 ℃.
(11) And (4) carrying out photoresist removal treatment on the ultraviolet photoelectric detector epitaxial wafer deposited in the step (10): the epitaxial wafer is respectively soaked in acetone and absolute ethyl alcohol for ultrasonic treatment for 3min, photoresist and redundant passivation layers on the surface of the epitaxial wafer are dissolved, and then the epitaxial wafer is washed by deionized water and dried under hot high-purity nitrogen.
(12) And (4) scribing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (11), and separating out an independent small device to obtain the nonpolar a-plane GaN asymmetric MSM structure ultraviolet photoelectric detector.
In the embodiment of the invention, the nonpolar a-plane GaN-based ultraviolet photoelectric detector has very good low dark current performance under reverse bias; and the test result is similar to that of embodiment 2, and the details are not repeated herein.
Example 5:
the embodiment provides a preparation method of a nonpolar a-plane GaN asymmetric MSM structure ultraviolet photodetector, which specifically comprises the following steps:
(1) as shown in figure 1, a metallorganic chemical vapor deposition technology is adopted to grow an ultraviolet photoelectric detector epitaxial wafer on a r-plane sapphire substrate 1, wherein the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-plane AlN buffer layer 2 and a nonpolar a-plane Al with gradually changed componentsxGa1-xAn N buffer layer 3 and a nonpolar a-plane GaN epitaxial layer 4, wherein:
the nonpolar a-plane AlN buffer layer 2 grows on the r-plane sapphire substrate, and the thickness is 200 nm;
non-polar a-plane Al with gradually changed compositionxGa1-xThe N buffer layer 3 grows on the nonpolar a-surface AlN buffer layer 2, and the thickness is 600 nm;
the nonpolar a-surface GaN epitaxial layer grows on the nonpolar a-surface Al with gradually changed componentsxGa1-xThe N buffer layer 3 was formed to have a thickness of 4 μm.
(2) And (2) cleaning the surface of the ultraviolet photoelectric detector epitaxial wafer obtained in the step (1), soaking the ultraviolet photoelectric detector epitaxial wafer by using acetone and absolute ethyl alcohol in sequence, cleaning the surface for 3min by using ultrasonic waves, washing the surface by using deionized water after cleaning, and drying the surface in hot high-purity nitrogen.
(3) Photoetching the ultraviolet photoelectric detector epitaxial wafer obtained in the step (2): dripping a proper amount of positive photoresist with the model number of RZJ304 on the surface of the ultraviolet photoelectric detector epitaxial wafer, placing the ultraviolet photoelectric detector epitaxial wafer in a spin coater for processing, and spin-coating for 30s at the rotating speed of 3600 r/min to uniformly cover the photoresist on the surface with the thickness of 0.2 mu m; then prebaking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at 95 ℃, then placing the ultraviolet photoelectric detector epitaxial wafer into a photoetching machine, and aligning by adopting a mask plate with asymmetric electrodes, wherein the detector parameters of the mask plate are that the width of a small electrode is 5 mu m, the width of a large electrode is 15 mu m, the distance between interdigital electrodes is 10 mu m, and the number of electrode pairs is 8; exposure was then carried out for 15 s.
(4) Soaking the exposed epitaxial wafer of the ultraviolet photoelectric detector in the step (3) in positive developing solution for 60s, wherein the model of the developing solution is RZX 3038; and cleaning the substrate with deionized water after the development is finished, drying the substrate with hot high-purity nitrogen, and then placing the substrate on a hot plate furnace for post-baking for 90 s.
(5) And (5) observing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (4) under a microscope, determining that the photoresist in the electrode area is completely removed, and only leaving the isolation pattern in the non-electrode area.
(6) Placing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (5) in an electron beam evaporation device for evaporating electrodes, and keeping the vacuum degree in a cavity at 5 multiplied by 10-5Pa, firstly evaporating a Ni metal electrode with the thickness of 30nm at the evaporation rate of 0.1nm/s, then evaporating an Au metal electrode with the thickness of 270nm at the evaporation rate of 1nm/s, wherein the total electrode thickness is 300nm, annealing at 900 ℃ for 30s after evaporation is finished to obtain the asymmetric Schottky interdigital electrode 6, and finally annealing at 900 ℃ for 80 min.
(7) And (4) carrying out photoresist removing treatment on the ultraviolet photoelectric detector epitaxial wafer obtained in the step (6): after the temperature is reduced to room temperature, the mixture is placed in acetone and absolute ethyl alcohol in sequence for ultrasonic treatment for 3min, then is washed by deionized water, and is dried by hot high-purity nitrogen.
(8)Si3N4Preparing a passivation layer isolation pattern: and (5) photoetching the ultraviolet photoelectric detector epitaxial wafer obtained in the step (7): dripping a proper amount of negative photoresist (RFJ-210) on the surface of the epitaxial wafer of the ultraviolet photoelectric detector, placing the epitaxial wafer in a spin coater for processing, and spin-coating the photoresist for 30s at the rotating speed of 3600 r/min to ensure that the photoresist on the surface is uniformly covered with the thickness of 0.2 mu m; then prebaking the ultraviolet photoelectric detector epitaxial wafer coated with the photoresist for 90s at 95 ℃, then placing the ultraviolet photoelectric detector epitaxial wafer in a photoetching machine, aligning by adopting a mask plate with an asymmetric electrode, and then exposing for 15 s; then, placing the exposed epitaxial wafer of the ultraviolet photoelectric detector in a developing solution to be soaked for 60s, wherein the model is RFX-2277; and cleaning with deionized water after the development is finished, blow-drying with hot high-purity nitrogen, and placing on a hot plate furnace for post-baking for 90 s.
(9) And (5) observing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (8) under a microscope, determining that the photoresist in the non-electrode area is completely removed, and only leaving the isolation pattern in the electrode area.
(10) Depositing a layer of Si with the thickness of 160nm on the surface of the obtained ultraviolet photoelectric detector epitaxial wafer by adopting a plasma-assisted chemical vapor deposition method3N4And the deposition temperature of the passivation layer 5 is 850 ℃.
(11) And (4) carrying out photoresist removal treatment on the ultraviolet photoelectric detector epitaxial wafer deposited in the step (10): the epitaxial wafer is respectively soaked in acetone and absolute ethyl alcohol for ultrasonic treatment for 3min, photoresist and redundant passivation layers on the surface of the epitaxial wafer are dissolved, and then the epitaxial wafer is washed by deionized water and dried under hot high-purity nitrogen.
(12) And (4) scribing the ultraviolet photoelectric detector epitaxial wafer obtained in the step (11), and separating out an independent small device to obtain the nonpolar a-surface GaN asymmetric MSM structure ultraviolet photoelectric detector.
In the embodiment of the invention, the nonpolar a-surface AlN buffer layer and the nonpolar a-surface Al with gradually changed componentsxGa1-xThe N buffer layer and the nonpolar a-surface GaN epitaxial layer are thicker, so that the defect density of the ultraviolet photoelectric detector epitaxial wafer can be effectively reduced; moreover, the interdigital distance is wider, the thickness of a passivation layer is larger, the responsivity of the detector is improved to a great extent, and the detector has good visible blind characteristics and very sensitive detection capability on ultraviolet light; while having very good low dark current performance under reverse bias.
In summary, the invention discloses a preparation method of a nonpolar a-surface GaN asymmetric MSM structure ultraviolet photoelectric detector, which comprises the steps of growing a nonpolar a-surface AlN buffer layer and a nonpolar a-surface Al with gradually changed components on a r-surface sapphire substrate in sequencexGa1-xObtaining an ultraviolet photoelectric detector epitaxial wafer by using the N buffer layer and the nonpolar a-surface GaN epitaxial layer; depositing a layer of Si on the epitaxial wafer of the ultraviolet photoelectric detector3N4Preparing a passivation layer, preparing an electrode channel pattern, etching the passivation layer at the electrode groove by wet etching, and depositing a metal electrode at the etched part randomlyAnd finally, removing the photoresist, and scribing and separating the devices. The invention also discloses another preparation method, namely preparing the electrode isolation pattern, depositing the metal electrode to form the asymmetric MSM electrode structure of Schottky contact; then, the metal electrode is isolated by adopting the photoetching technology, and a layer of Si is deposited in the area which is not covered by the metal electrode3N4And passivating the layer, finally removing the photoresist, and scribing and separating the device. The invention realizes the preparation of the high-performance nonpolar a-surface GaN-based ultraviolet photoelectric detector, improves the response rate of the nonpolar a-surface GaN-based ultraviolet photoelectric detector and reduces the dark current of the device.
The above description is only for the preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the scope of the present invention.
Claims (10)
1. The nonpolar a-surface GaN-based ultraviolet photoelectric detector is characterized by comprising an ultraviolet photoelectric detector epitaxial wafer and Si deposited on the ultraviolet photoelectric detector epitaxial wafer3N4Passivation layer, and the schottky interdigital electrode of asymmetric MSM structure, wherein:
the ultraviolet photoelectric detector epitaxial wafer comprises a nonpolar a-surface AlN buffer layer and a nonpolar a-surface Al with gradually changed components, which sequentially grow on a r-surface sapphire substratexGa1-xThe GaN substrate comprises an N buffer layer and a nonpolar a-plane GaN epitaxial layer, wherein x is 0.2-0.8;
said Si3N4The passivation layer is arranged on the nonpolar a-surface GaN epitaxial layer;
the Schottky interdigital electrode penetrates through the Si3N4And the passivation layer is in direct contact with the nonpolar a-surface GaN epitaxial layer on the ultraviolet photoelectric detector epitaxial wafer.
2. The nonpolar a-plane GaN-based ultraviolet photodetector of claim 1, wherein the Schottky interdigital electrode is made of evaporated electrode metal, the electrode metal is sequentially stacked from bottom to top from Ni/Au, and the total electrode thickness is 200-300 nm.
3. The nonpolar a-surface GaN-based ultraviolet photoelectric detector according to claim 1, wherein the widths of the large and small interdigital electrodes in the Schottky interdigital electrode are 5-15 μm, the distance between the large and small interdigital electrodes is 5-10 μm, and the width of the large interdigital electrode is larger than that of the small interdigital electrode.
4. The non-polar a-plane GaN-based ultraviolet photodetector of claim 1, wherein the r-plane sapphire substrate is epitaxial from 10-12 planes to 1-100 directions by 0.1 °, and the non-polar a-plane AlN buffer layer and the non-polar a-plane Al buffer layer are formed on the substratexGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are both arranged such that the 0001 plane is parallel to the-1011 plane of the r-plane sapphire, and the a plane is used as an epitaxial plane.
5. The non-polar a-plane GaN-based ultraviolet photodetector according to claim 1, wherein the thickness of the non-polar a-plane AlN buffer layer is 120-200 nm, and the thickness of the non-polar a-plane Al buffer layer isxGa1-xThe thickness of the N buffer layer is 450-600 nm, the thickness of the a-surface GaN epitaxial layer is 3-4 mu m, and the thickness of the Si buffer layer is3N4The thickness of the passivation layer is 120-160 nm.
6. The non-polar a-plane GaN-based ultraviolet photodetector of claim 1, wherein the sapphire thickness at r-plane is 400 μ ι η.
7. A preparation method of a nonpolar a-surface GaN-based ultraviolet photoelectric detector is characterized by comprising the following steps:
sequentially growing a nonpolar a-surface AlN buffer layer and nonpolar a-surface Al on a r-surface sapphire substratexGa1-xObtaining an epitaxial wafer of the ultraviolet photoelectric detector by the N buffer layer and the nonpolar a-surface GaN epitaxial layer and carrying out pretreatment, wherein,x＝0.2～0.8；
depositing Si on the surface of the pretreated ultraviolet photoelectric detector epitaxial wafer by adopting a plasma-assisted chemical vapor deposition method3N4A passivation layer;
to deposit Si3N4Coating positive photoresist on the surface of the ultraviolet photoelectric detector epitaxial wafer of the passivation layer, and forming an asymmetric interdigital electrode by using a mask plate to obtain an electrode channel pattern;
wet etching is carried out on the ultraviolet photoelectric detector epitaxial wafer with the electrode channel pattern, and Si in a window area which is not covered by the photoresist is etched3N4Passivating the layer to obtain an asymmetric Schottky electrode groove;
placing the etched ultraviolet photoelectric detector epitaxial wafer into electron beam evaporation equipment, evaporating electrode metal to obtain a Schottky interdigital electrode with an asymmetric MSM structure, and annealing; wherein the Schottky inter-digital electrode penetrates the Si3N4The passivation layer is in direct contact with the nonpolar a-surface GaN epitaxial layer;
and processing and scribing the ultraviolet photoelectric detector epitaxial wafer of the obtained Schottky interdigital electrode, and separating out independent small devices to obtain the nonpolar a-surface GaN-based ultraviolet photoelectric detector.
8. The method according to claim 7, wherein the r-plane sapphire substrate has an epitaxial plane with a 10-12 plane offset by 0.1 ° in a 1-100 direction, the non-polar a-plane AlN buffer layer, and the non-polar a-plane AlxGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are both arranged such that the 0001 plane is parallel to the-1011 plane of the r-plane sapphire, and the a plane is used as an epitaxial plane.
9. A preparation method of a nonpolar a-plane GaN-based ultraviolet photoelectric detector is characterized by comprising the following steps:
sequentially growing a nonpolar a-surface AlN buffer layer and a nonpolar a-surface Al on an r-surface sapphire substratexGa1-xObtaining an N buffer layer and a nonpolar a-plane GaN epitaxial layer, obtaining an ultraviolet photoelectric detector epitaxial wafer and preprocessing the ultraviolet photoelectric detector epitaxial wafer, wherein x is equal to0.2～0.8；
Coating a positive photoresist on the surface of the pretreated ultraviolet photoelectric detector epitaxial wafer, and forming an asymmetric interdigital electrode by using a mask to obtain an electrode channel pattern;
placing the ultraviolet photoelectric detector epitaxial wafer with the prepared electrode channel pattern into electron beam evaporation equipment, evaporating electrode metal to obtain a Schottky interdigital electrode with an asymmetric structure, and annealing;
coating negative photoresist on the surface of an epitaxial wafer of the ultraviolet photoelectric detector with the Schottky interdigital electrode, and forming an asymmetric interdigital electrode by using a mask plate to obtain an electrode isolation pattern;
placing the ultraviolet photoelectric detector epitaxial wafer with the prepared electrode isolation pattern in plasma-assisted chemical vapor deposition equipment to deposit Si3N4A passivation layer;
removing deposited Si3N4And (4) scribing photoresist on the ultraviolet photoelectric detector epitaxial wafer of the passivation layer, and separating out an independent small device to obtain the nonpolar a-surface GaN-based ultraviolet photoelectric detector.
10. The method of claim 9, wherein the r-plane sapphire substrate has an epitaxial plane with a 10-12 plane offset by 0.1 ° in a 1-100 direction, the non-polar a-plane AlN buffer layer, and the non-polar a-plane AlxGa1-xThe N buffer layer and the nonpolar a-plane GaN epitaxial layer are both arranged such that the 0001 plane is parallel to the-1011 plane of the r-plane sapphire, and the a plane is used as an epitaxial plane.
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