Tunable dual-band ultraviolet photoelectric detector and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor structures, and discloses a tunable dual-band ultraviolet photoelectric detector and a preparation method thereof, and the tunable dual-band ultraviolet photoelectric detector comprises a substrate; the buffer gallium nitride layer is located on the surface of one side of the substrate; the P-type gallium nitride layer is located on the surface of the side, opposite to the substrate, of the buffer gallium nitride layer; the gallium oxide layer is located on the surface of one side, opposite to the buffer gallium nitride layer, of the P-type gallium nitride layer; the second electrode is positioned on the surface of the P-type gallium nitride layer on the side part of the gallium oxide layer; the second electrode is in electric contact with the P-type gallium nitride layer; the interdigital electrode is located on the surface of one side, opposite to the P-type gallium nitride layer, of the gallium oxide layer; the interdigital electrode comprises a first electrode and a third electrode, and the first electrode and the third electrode are respectively in electric contact with the gallium oxide layer. Compared with the prior art, the tunable dual-band ultraviolet light detection can be realized on a single photoelectric detector, the detection efficiency is improved, and the application scene of the device is widened.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor structures, and in particular to a tunable dual-band ultraviolet photoelectric detector and a preparation method thereof. Background Art

[0002] Ultraviolet photodetectors can convert ultraviolet light into electrical signals and are widely used in many fields such as ultraviolet communications, corona discharge detection, and medical imaging. Dual-band photodetection devices can use the differences in light response characteristics within the band to identify dual-band information, fuse and generate a more complete information description of the scene, and realize complex environmental light detection. Generally, two independent photodetectors are used to construct a dual-band photodetector, which is dual-detector dual-band imaging. However, integrating two complete detectors in the same device is much more difficult than the preparation of a single-band detector, whether it is material growth or device design and preparation.

[0003] In one solution of the related technology, gallium oxide and gallium nitride are formed into a heterojunction device, which can detect dual-band ultraviolet light at the same time. However, it is impossible to detect ultraviolet light of a certain band specifically according to demand, so tunable dual-band ultraviolet light detection cannot be achieved. Summary of the invention

[0004] In view of this, the present invention provides a tunable dual-band ultraviolet photodetector and a preparation method thereof to solve the problem in the related art that only ultraviolet light of a fixed band can be detected and tunable dual-band ultraviolet light detection cannot be achieved in a single ultraviolet photodetector.

[0005] In a first aspect, the present invention provides a tunable dual-band ultraviolet photodetector, the tunable dual-band ultraviolet photodetector comprising:

[0006] substrate;

[0007] A buffer gallium nitride layer is located on one side surface of the substrate;

[0008] A P-type gallium nitride layer is located on a surface of the buffer gallium nitride layer facing away from the substrate;

[0009] A gallium oxide layer, located on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer;

[0010] A second electrode is located on a surface of the P-type gallium nitride layer at a side of the gallium oxide layer; the second electrode forms an electrical contact with the P-type gallium nitride layer;

[0011] The interdigitated electrodes are located on a surface of the gallium oxide layer facing away from the P-type gallium nitride layer; the interdigitated electrodes include a first electrode and a third electrode, and the first electrode and the third electrode are in electrical contact with the gallium oxide layer respectively.

[0012] The tunable dual-band ultraviolet photodetector provided by the present invention, on the one hand, can effectively improve lattice matching, improve surface flatness, relieve stress, enhance device performance, etc. by introducing a buffer gallium nitride layer, which can ensure the high quality, stability and reliability of the P-type gallium nitride layer, thereby improving the stability and reliability of the device; on the other hand, unlike the common two-terminal device, this three-terminal device is composed of a photoconductive device and a PN junction device, and light detection in different bands can be achieved by simply changing the bias voltage. In addition, the third electrode and the first electrode form a pair of interdigitated electrodes, which can form a uniform electric field distribution and optimize the utilization of the illuminated area. Moreover, the interdigitated electrodes reduce the parallel current path at the electrode interval through the staggered design structure, which helps to reduce parasitic capacitance. The tunable dual-band ultraviolet photodetector provided by the present invention can detect only the ultraviolet light detection band corresponding to the gallium oxide layer, or only detect the ultraviolet light detection band corresponding to the gallium nitride layer, or simultaneously detect the ultraviolet light detection dual bands corresponding to the gallium oxide layer and the gallium nitride layer by changing the bias voltage, thereby realizing tunable dual-band ultraviolet light detection on a single ultraviolet photodetector, making it easier to detect ultraviolet light in different bands, improving detection efficiency, broadening the application scenarios of the device, and improving the stability and reliability of the device.

[0013] In an optional embodiment, the material of the second electrode is Ni / Au;

[0014] The materials of the first electrode and the third electrode are Ti / Au.

[0015] In an optional embodiment, the thickness of Ni in the second electrode is 20 nm, and the thickness of Au is 50 nm;

[0016] The thickness of Ti in the first electrode and the third electrode is 10 nm, and the thickness of Au is 50 nm.

[0017] In an optional embodiment, the second electrode is a ring electrode;

[0018] The second electrode surrounds the side of the gallium oxide layer, and there is a gap between the second electrode and the gallium oxide layer.

[0019] The tunable dual-band ultraviolet photodetector provided by the present invention sets the second electrode as a ring electrode surrounding the side of the gallium oxide layer, so that a uniform electric field distribution can be formed inside the gallium oxide layer contacted by the second electrode, and the ring electrode can reduce the concentration of the electric field by surrounding the PN junction, so that the carriers in the entire PN junction area can be effectively collected, thereby improving the detection efficiency and accuracy.

[0020] In an optional embodiment, the gallium oxide layer is rectangular in top view;

[0021] The gallium oxide layer has a length of 800 μm to 1000 μm and a width of 300 μm to 500 μm;

[0022] The line width of the second electrode is 1 μm to 100 μm;

[0023] The interval between the second electrode and the gallium oxide layer is 1 μm to 100 μm.

[0024] In an optional embodiment, the thickness of the gallium oxide layer is 90 nm to 100 nm;

[0025] The doping material of the P-type GaN layer is Mg, and the doping concentration is 10 17 cm -3 ~10 19 cm -3 ;

[0026] The thickness of the P-type gallium nitride layer is 150nm to 200nm;

[0027] The buffer gallium nitride layer is an unintentionally doped gallium nitride layer;

[0028] The thickness of the buffer gallium nitride layer is 4 μm to 5 μm.

[0029] The tunable dual-band ultraviolet photodetector provided by the present invention uses an unintentionally doped gallium nitride layer as a buffer gallium nitride layer to effectively improve lattice matching, improve surface flatness, relieve stress, enhance electrical performance, provide a high-quality template, and reduce optical performance degradation, etc., which can ensure the high quality, stability and reliability of the P-type gallium nitride layer, thereby improving the stability and reliability of the device.

[0030] In an optional implementation, the first electrode is a detection electrode; the third electrode is grounded; and the second electrode is suitable for accessing a potential less than or equal to 0V.

[0031] When the voltage between the first electrode and the third electrode is a first target voltage, the first electrode only detects ultraviolet light in the first wavelength band;

[0032] When the voltage between the first electrode and the third electrode is a second target voltage, the first electrode only detects ultraviolet light in the second wavelength band;

[0033] When the voltage between the first electrode and the third electrode is between the first target voltage and the second target voltage, the first electrode can detect ultraviolet light in the first wavelength band and the second wavelength band at the same time.

[0034] The tunable dual-band ultraviolet photodetector provided by the present invention has a first electrode as a detection electrode. When the first electrode is at a first target voltage, the first electrode only detects ultraviolet light in the first band, and the light response in the second band is greatly weakened or even completely eliminated; when the first electrode is at a second target voltage, the first electrode only detects ultraviolet light in the second band, and the light response in the first band is greatly weakened or even completely eliminated; when the voltage of the first electrode is between the first target voltage and the second target voltage, the first electrode can simultaneously detect ultraviolet light in the first band and the second band; tunable dual-band ultraviolet light detection can be achieved on a single ultraviolet photodetector, making it easier to detect ultraviolet light in different bands, improving detection efficiency, and broadening the application scenarios of the device.

[0035] In an optional embodiment, the first waveband is 200nm to 260nm; the second waveband is 260nm to 360nm;

[0036] The first target voltage is the second electrode potential minus 0.6V; the second target voltage is -0.3V to 0V.

[0037] In a second aspect, the present invention provides a method for preparing a tunable dual-band ultraviolet photodetector, which is used to prepare the tunable dual-band ultraviolet photodetector of the first aspect, and the preparation method comprises:

[0038] providing a substrate;

[0039] forming a buffer gallium nitride layer on a surface of one side of the substrate;

[0040] forming a P-type gallium nitride layer on a surface of the buffer gallium nitride layer facing away from the substrate;

[0041] forming a gallium oxide layer on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer;

[0042] A second electrode is formed on the surface of the P-type gallium nitride layer at the side of the gallium oxide layer; the second electrode forms an electrical contact with the P-type gallium nitride layer;

[0043] An interdigitated electrode is formed on a surface of the gallium oxide layer facing away from the P-type gallium nitride layer; the interdigitated electrode includes a first electrode and a third electrode, and the first electrode and the third electrode are in electrical contact with the gallium oxide layer respectively.

[0044] The preparation method of the tunable dual-band ultraviolet photodetector provided by the present invention, on the one hand, can effectively improve lattice matching, improve surface flatness, relieve stress, enhance device performance, etc. by forming a buffer gallium nitride layer on the surface of the substrate, which can provide necessary support and guarantee for the subsequent formation of a high-quality P-type gallium nitride layer, thereby improving the stability and reliability of the device; on the other hand, unlike the common two-terminal device, this three-terminal device is composed of a photoconductive device and a PN junction device, and light detection in different bands can be achieved by simply changing the bias voltage. In addition, the third electrode formed on the gallium oxide layer and the first electrode form a pair of interdigitated electrodes, which can form a uniform electric field distribution and optimize the utilization of the illuminated area at the same time. Moreover, the interdigitated electrodes reduce the parallel current path at the electrode interval through the staggered design structure, which helps to reduce parasitic capacitance. The tunable dual-band ultraviolet photodetector prepared by the preparation method of the tunable dual-band ultraviolet photodetector provided by the present invention can detect only the ultraviolet light detection band corresponding to the gallium oxide layer, or only detect the ultraviolet light detection band corresponding to the gallium nitride layer, or simultaneously detect the ultraviolet light detection dual bands corresponding to the gallium oxide layer and the gallium nitride layer by changing the bias voltage according to needs, thereby realizing tunable dual-band ultraviolet light detection on a single ultraviolet photodetector, making it easier to detect ultraviolet light in different bands, improving detection efficiency, broadening the application scenarios of the device, and at the same time improving the stability and reliability of the device.

[0045] In an optional embodiment, the step of forming a gallium oxide layer on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer includes:

[0046] Growing an epitaxial gallium oxide film on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer;

[0047] Performing patterned photolithography and etching processes on the gallium oxide film to form a patterned gallium oxide layer;

[0048] The step of forming a second electrode on the surface of the P-type gallium nitride layer at the side of the gallium oxide layer includes:

[0049] Coating a photoresist on the surface of the P-type gallium nitride layer, exposing the photoresist and developing it to obtain a patterned photoresist corresponding to the second electrode;

[0050] Ni / Au is evaporated on the surface of the patterned photoresist to form a second electrode, and the patterned photoresist is removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related technologies, the drawings required for use in the specific embodiments or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are 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.

[0052] Figure 1 Schematic diagram of the structure of a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention.

[0053] Figure 2 4 is a top view of a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention.

[0054] Figure 3 Schematic diagram of a current-voltage curve of a tunable dual-band ultraviolet photodetector in logarithmic coordinates according to an embodiment of the present invention.

[0055] Figure 4 It is a schematic flow chart of a method for preparing a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention.

[0056] Figure 5 It is a schematic structural diagram of a method for preparing a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention after epitaxially growing a gallium oxide film.

[0057] Figure 6 In a method for preparing a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention, Figure 5 Schematic diagram of the structure of a patterned gallium oxide layer formed on the basis.

[0058] Figure 7 In a method for preparing a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention, Figure 6 Schematic diagram of the structure of the second electrode on the basis.

[0059] Figure 8 In a method for preparing a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention, Figure 7 Schematic diagram of the structure of the interdigitated electrodes formed on the basis.

[0060] Fig. 9 It is a specific flow chart of a method for preparing a tunable dual-band ultraviolet photodetector according to an embodiment of the present invention.

[0061] Reference numerals:

[0062] 1. Gallium nitride layer; 3. Gallium oxide layer; 2. Gallium nitride contact electrode; 4. Gallium oxide contact electrode; 10. Substrate; 20. Buffer gallium nitride layer; 30. P-type gallium nitride layer; 40. Gallium oxide layer; 51. First electrode; 52. Second electrode; 53. Third electrode. DETAILED DESCRIPTION

[0063] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0064] In the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified for the purpose of clear expression, and some details may be omitted. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships between them are only exemplary, and may be deviated due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be a middle layer / element between them. In addition, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "under" the other layer / element.

[0065] Ultraviolet photodetectors can convert ultraviolet light into electrical signals and are widely used in many fields such as ultraviolet communications, corona discharge detection, and medical imaging. Dual-band photodetection devices can use the differences in light response characteristics within the band to identify dual-band information, fuse and generate a more complete information description of the scene, and realize complex environmental light detection. In the early days, two independent photodetectors were mainly used to construct dual-band photodetectors, that is, dual-detector dual-band imaging. However, integrating two complete detectors in the same device is much more difficult than the preparation of single-band detectors, whether it is material growth or device design and preparation.

[0066] Gallium oxide (Ga2O3) is an important new type of ultra-wide bandgap oxide semiconductor material, which has attracted much attention due to its superior material properties. Compared with other wide bandgap semiconductor materials, Ga2O3 has higher breakdown voltage, lower on-resistance and higher Baliga figure of merit. At the same time, as a solar-blind band oxide semiconductor material, Ga2O3 has a very suitable bandwidth (~4.9eV). Its photoresponse peak is located in the solar-blind UV band, and the absorption coefficient near the absorption edge is as high as 10 5 cm -1 Therefore, Ga2O3 can be used as a natural solar-blind ultraviolet detector material without complicated alloying. Gallium nitride (GaN) is also a new type of semiconductor material with a relatively narrow bandgap of about 3.4eV. Due to its good photoelectric properties, it is often used to prepare optoelectronic devices. After combining the two to form a heterojunction, the light absorption range of the device can be broadened. At the same time, the lattice mismatch between the two is very small (~4.7%), and Ga2O3 has a high transmittance (>80%) for visible light and ultraviolet light.

[0067] like Figure 1 and Figure 2 As shown, this embodiment provides a tunable dual-band ultraviolet photodetector, and the tunable dual-band ultraviolet photodetector includes:

[0068] Substrate 10;

[0069] A buffer gallium nitride layer 20 is located on one side surface of the substrate 10;

[0070] The P-type gallium nitride layer 30 is located on the surface of the buffer gallium nitride layer 20 facing away from the substrate 10;

[0071] The gallium oxide layer 40 is located on a surface of the P-type gallium nitride layer 30 facing away from the buffer gallium nitride layer 20 ;

[0072] A second electrode 52 is located on the surface of the P-type gallium nitride layer 30 at the side of the gallium oxide layer 40; the second electrode 52 forms an electrical contact with the P-type gallium nitride layer 30;

[0073] The interdigitated electrodes are located on a surface of the gallium oxide layer 40 facing away from the P-type gallium nitride layer 30 . The interdigitated electrodes include a first electrode 51 and a third electrode 53 . The first electrode 51 and the third electrode 53 are in electrical contact with the gallium oxide layer 40 , respectively.

[0074] In specific implementation, the substrate 10 can be made of silicon, silicon nitride, sapphire and other substrate materials. Since the self-compensation of oxygen vacancies in gallium oxide (Ga2O3) makes Ga2O3 generally behave as N-type, an undoped gallium oxide layer is selected as the N-type layer, and the P-type gallium nitride layer 30 and the gallium oxide layer 40 form a PN junction heterojunction.

[0075] Compared with traditional unipolar devices, bipolar devices have the advantages of lower background noise, smaller leakage current and higher frequency bandwidth. Due to the self-compensation effect of gallium oxide, its P-type doping is difficult to achieve, and it usually forms a heterojunction with other P-type materials. Gallium nitride and gallium oxide have relatively small lattice mismatch, and both have wide band gaps, high breakdown fields and clear crystallographic relationships. Therefore, a P-type gallium nitride layer is selected to form a heterojunction bipolar device with the gallium oxide layer. When the detector is working, only the P-type gallium nitride layer and the gallium oxide layer participate in ultraviolet light detection, and the buffer gallium nitride layer only acts as a buffer layer and does not participate in ultraviolet light detection. The P-type gallium nitride layer and the gallium oxide layer are detected simultaneously. The ultraviolet cutoff absorption boundary of the gallium oxide layer is approximately around 254nm, so the detection range of gallium oxide is mainly concentrated in the ultraviolet (UV) region, especially the UVC band, that is, approximately between 200nm and 280nm. For light with a wavelength greater than 254nm, the light absorption ability of gallium oxide is greatly weakened because the energy of the photon is not enough to excite electron transitions. The cutoff wavelength corresponding to the gallium nitride layer is around 365nm, which means that the gallium nitride detector can effectively detect ultraviolet light below 365nm, especially: UVA band (320nm to 400nm), UVB band (280nm to 320nm). Gallium nitride can also detect light in the UVC band (200nm to 280nm), but its efficiency is lower because the light energy in this band is higher and may exceed the photon energy that can be absorbed by the gallium nitride band gap.

[0076] The tunable dual-band ultraviolet photodetector specifically detects ultraviolet light as follows: when the operating voltage is a specific voltage, it only responds to ultraviolet light in the ultraviolet light detection band corresponding to the gallium oxide layer, and at another specific voltage, it only responds to ultraviolet light in the ultraviolet light detection band corresponding to the gallium nitride layer. Between these two voltages, the entire device can exhibit a wide-spectrum response of ultraviolet light detection dual bands corresponding to the gallium oxide layer and the gallium nitride layer. Moreover, this design only has a photosensitive detection area located on one side of the gallium oxide layer, which can achieve tunable dual-band light detection.

[0077] The tunable dual-band ultraviolet photodetector provided in this embodiment, on the one hand, can effectively improve lattice matching, improve surface flatness, relieve stress, enhance device performance, etc. by introducing a buffer gallium nitride layer, which can ensure the high quality, stability and reliability of the P-type gallium nitride layer, thereby improving the stability and reliability of the device; on the other hand, unlike the common two-terminal device, this three-terminal device is composed of a photoconductive device and a PN junction device, and light detection in different bands can be achieved by simply changing the bias voltage. In addition, the newly introduced third electrode and the first electrode form a pair of interdigitated electrodes, which can form a uniform electric field distribution and optimize the utilization of the illuminated area. Moreover, the interdigitated electrodes reduce the parallel current path at the electrode interval through the staggered design structure, which helps to reduce parasitic capacitance. The tunable dual-band ultraviolet photodetector provided in this embodiment can detect only the ultraviolet light detection band corresponding to the gallium oxide layer, or only detect the ultraviolet light detection band corresponding to the gallium nitride layer, or simultaneously detect the ultraviolet light detection dual bands corresponding to the gallium oxide layer and the gallium nitride layer by changing the bias voltage, thereby realizing tunable dual-band ultraviolet light detection on a single ultraviolet photodetector, making it easier to detect ultraviolet light in different bands, improving detection efficiency, broadening the application scenarios of the device, and improving the stability and reliability of the device.

[0078] In some optional embodiments, the material of the second electrode 52 is Ni / Au;

[0079] The materials of the first electrode 515 and the third electrode 53 are Ti / Au.

[0080] In some optional embodiments, the thickness of Ni in the second electrode 52 is 20 nm, and the thickness of Au is 50 nm;

[0081] The thickness of Ti in the first electrode 51 and the third electrode 53 is 10 nm, and the thickness of Au is 50 nm.

[0082] In some optional embodiments, the second electrode 52 is a ring electrode;

[0083] The second electrode 52 surrounds the side of the gallium oxide layer 40 , and there is a gap between the second electrode 52 and the gallium oxide layer 40 .

[0084] In traditional planar electrode designs, the electric field may be more concentrated around the electrode, resulting in an uneven electric field in the illuminated area.

[0085] The tunable dual-band ultraviolet photodetector provided in this embodiment sets the second electrode as a ring electrode surrounding the side of the gallium oxide layer, so that a uniform electric field distribution can be formed inside the gallium oxide layer in contact with the second electrode. The ring electrode can reduce the concentration of the electric field by surrounding the PN junction, so that the carriers in the entire PN junction area can be effectively collected, thereby improving the ultraviolet light detection efficiency and accuracy of the device.

[0086] In some optional embodiments, the gallium oxide layer 40 is rectangular in a top view;

[0087] The gallium oxide layer 40 has a length of 800 μm to 1000 μm, such as 800 μm, 850 μm, 900 μm, 950 μm or 1000 μm, and a width of 300 μm to 500 μm, such as 300 μm, 350 μm, 400 μm, 450 μm or 500 μm;

[0088] The line width of the second electrode is 1 μm to 100 μm;

[0089] The distance between the second electrode and the gallium oxide layer 40 is 1 μm to 100 μm.

[0090] In some optional embodiments, the gallium oxide layer 40 has a thickness of 90 nm to 100 nm, for example, 90 nm, 93 nm, 95 nm, 98 nm or 100 nm;

[0091] The doping material of the P-type GaN layer is Mg, and the doping concentration is 10 17 cm -3 ~10 19 cm -3 ;

[0092] The thickness of the P-type gallium nitride layer is 150 nm to 200 nm, for example, 150 μm, 160 μm, 170 μm, 180 μm or 200 μm;

[0093] The buffer gallium nitride layer is an unintentionally doped gallium nitride layer;

[0094] The buffer gallium nitride layer has a thickness of 4 μm to 5 μm, for example, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm or 5 μm.

[0095] The tunable dual-band ultraviolet photodetector provided in this embodiment uses the unintentionally doped gallium nitride layer as a buffer gallium nitride layer to effectively improve lattice matching, improve surface flatness, relieve stress, enhance device performance, etc., and can ensure the high quality, stability and reliability of the P-type gallium nitride layer, thereby improving the stability and reliability of the device.

[0096] In some optional embodiments, the first electrode 51 is a detection electrode; the third electrode 53 is grounded; the second electrode 52 is suitable for accessing a potential less than or equal to 0V;

[0097] When the voltage between the first electrode 51 and the third electrode 53 is the first target voltage, the first electrode 51 only detects ultraviolet light in the first wavelength band;

[0098] When the voltage between the first electrode 51 and the third electrode 53 is the second target voltage, the first electrode 51 only detects ultraviolet light in the second wavelength band;

[0099] When the voltage between the first electrode 51 and the third electrode 53 is between the first target voltage and the second target voltage, the first electrode 51 can detect ultraviolet light in the first wavelength band and the second wavelength band at the same time.

[0100] The working principle of the tunable dual-band ultraviolet photodetector is as follows: the device combines the PN junction type and the photoconductive type photodetectors. The two detectors can be made to work at different voltages by simply changing the bias voltage. It can be seen from the schematic diagram of the device structure that the current generated by the light corresponding to the gallium oxide layer (the first band) is composed of the photoconductive type photodetector composed of the first electrode and the third electrode and the PN junction type photodetector composed of the second electrode. Moreover, since the photocurrent of the photoconductive type photodetector is much larger than the photocurrent of the PN junction type photodetector, the size of the photogenerated current generated by the light corresponding to the gallium oxide layer (the first band) is almost only affected by the photoconductive type photodetector, while the current generated by the light corresponding to the gallium nitride layer (the second band) is all generated by the PN junction type photodetector. That is, when the voltage between the first electrode and the third electrode is the first target voltage, the built-in electric field of the PN junction photodetector is completely offset by the forward bias voltage, and the corresponding photogenerated current will be reduced to the minimum, while the photoconductive photodetector works normally under this voltage, so the first electrode only detects ultraviolet light in the first band at this time; when the voltage between the first electrode and the third electrode is the second target voltage, the potential between the first electrode and the third electrode is almost 0V, the photogenerated current corresponding to the photoconductive photodetector will be reduced to the minimum, while the PN junction photodetector still has photogenerated current, so the first electrode only detects ultraviolet light in the second band at this time.

[0101] The tunable dual-band ultraviolet photodetector provided in this embodiment has a first electrode as a detection electrode. When the voltage between the first electrode and the third electrode is a first target voltage, the first electrode only detects ultraviolet light in the first band, and the light response in the second band is greatly weakened or even completely eliminated; when the voltage between the first electrode and the third electrode is a second target voltage, the first electrode only detects ultraviolet light in the second band, and the light response in the first band is greatly weakened or even completely eliminated; when the voltage between the first electrode and the third electrode is between the first target voltage and the second target voltage, the first electrode can simultaneously detect ultraviolet light in the first band and the second band; tunable dual-band ultraviolet light detection can be achieved on a single ultraviolet photodetector, making it easier to detect ultraviolet light in different bands, improving detection efficiency, and broadening the application scenarios of the device.

[0102] In some optional embodiments, the first wavelength range is 200nm to 260nm; the second wavelength range is 260nm to 360nm;

[0103] The first target voltage is the third electrode potential minus 0.6V; the second target voltage is -0.3V to 0V.

[0104] In some optional embodiments, the second electrode and the third electrode are both grounded, and the first target voltage is -0.6 V and the second target voltage is 0 V. When the tunable dual-band ultraviolet photodetector detects, when the voltage between the first electrode 51 and the third electrode 53 is -0.6 V, the first electrode 51 only detects ultraviolet light in the first band; when the voltage between the first electrode 51 and the third electrode 53 is 0 V, the first electrode 51 only detects ultraviolet light in the second band; when the voltage between the first electrode 51 and the third electrode 53 is between -0.6 V and 0 V, the first electrode 51 can simultaneously detect ultraviolet light in the first band and the second band.

[0105] In some optional embodiments, the third electrode is grounded, and the potential of the second electrode is -2V. At this time, the first target voltage is -2.6V and the second target voltage is -0.2V. When the tunable dual-band ultraviolet photodetector detects, when the voltage between the first electrode 51 and the third electrode 53 is -2.6V, the first electrode 51 only detects ultraviolet light in the first band; when the voltage between the first electrode 51 and the third electrode 53 is -0.2V, the first electrode 51 only detects ultraviolet light in the second band; when the voltage between the first electrode 51 and the third electrode 53 is between -2.6V and 0V, the first electrode 51 can detect ultraviolet light in the first band and the second band at the same time. Figure 3 Schematic diagram of the current-voltage curve of the ultraviolet photodetector in this embodiment in logarithmic coordinates. It can be seen that at the first target voltage (-2.6V), 250nm ultraviolet light can be detected; at the second target voltage (-0.2V), 360nm ultraviolet light can be detected.

[0106] like Figure 4 As shown, this embodiment provides a method for preparing a tunable dual-band ultraviolet photodetector, and the preparation method includes but is not limited to steps S101 to S106.

[0107] Step S101, providing a substrate 10;

[0108] Step S102, forming a buffer gallium nitride layer 20 on one side surface of the substrate 10;

[0109] Step S103, forming a P-type gallium nitride layer 30 on the surface of the buffer gallium nitride layer 20 facing away from the substrate, such as Figure 5 As shown;

[0110] Step S104, forming a gallium oxide layer 40 on a surface of the P-type gallium nitride layer 30 facing away from the buffer gallium nitride layer 20, such as Figure 6 As shown;

[0111] Step S105, forming a second electrode 52 on the surface of the P-type gallium nitride layer 30 at the side of the gallium oxide layer 40; the second electrode 52 forms an electrical contact with the P-type gallium nitride layer 30, such as Figure 7 As shown;

[0112] Step S106, forming interdigital electrodes on the surface of the gallium oxide layer 40 facing away from the P-type gallium nitride layer 30; the interdigital electrodes include a first electrode 51 and a third electrode 53, and the first electrode 51 and the third electrode 53 are in electrical contact with the gallium oxide layer 40 respectively. Figure 8 shown.

[0113] The preparation method of the tunable dual-band ultraviolet photodetector provided in this embodiment, on the one hand, can effectively improve lattice matching, improve surface flatness, relieve stress, and enhance device performance by forming a buffer gallium nitride layer on the surface of the substrate, which can provide necessary support and guarantee for the subsequent formation of a high-quality P-type gallium nitride layer, thereby improving the stability and reliability of the device; on the other hand, unlike the common two-terminal device, this three-terminal device is composed of a photoconductive device and a PN junction device, and light detection in different bands can be achieved by simply changing the bias voltage. In addition, the third electrode formed on the gallium oxide layer and the first electrode form a pair of interdigitated electrodes, which can form a uniform electric field distribution and optimize the utilization of the illuminated area. Moreover, the interdigitated electrodes reduce the parallel current path at the electrode interval through the staggered design structure, which helps to reduce parasitic capacitance. The tunable dual-band ultraviolet photodetector prepared by the preparation method of the tunable dual-band ultraviolet photodetector provided in this embodiment can detect only the ultraviolet light detection band corresponding to the gallium oxide layer, or only detect the ultraviolet light detection band corresponding to the gallium nitride layer, or simultaneously detect the ultraviolet light detection dual bands corresponding to the gallium oxide layer and the gallium nitride layer by changing the bias voltage, thereby realizing tunable dual-band ultraviolet light detection on a single ultraviolet photodetector, making it easier to detect ultraviolet light in different bands, improving detection efficiency, broadening the application scenarios of the device, and improving the stability and reliability of the device.

[0114] In an optional embodiment, the step of forming the gallium oxide layer 40 on the surface of the P-type gallium nitride layer 30 facing away from the buffer gallium nitride layer 20 includes:

[0115] Growing an epitaxial gallium oxide film on a surface of the P-type gallium nitride layer 30 facing away from the buffer gallium nitride layer 20;

[0116] Performing patterning photolithography and etching processes on the gallium oxide film to form a patterned gallium oxide layer 40;

[0117] The step of forming the second electrode 52 on the surface of the P-type gallium nitride layer 30 on the side of the gallium oxide layer 40 includes:

[0118] A photoresist is coated on the surface of the P-type gallium nitride layer 30, and the photoresist is exposed and then developed to obtain a patterned photoresist corresponding to the second electrode 52;

[0119] Ni / Au is evaporated on the surface of the patterned photoresist to form a second electrode 52, and the patterned photoresist is removed.

[0120] like Fig. 9 As shown, the present invention also provides a specific process diagram of a method for preparing a tunable dual-band ultraviolet photodetector, comprising the following steps:

[0121] Step S201, providing a substrate 10, the substrate being a sapphire substrate;

[0122] In step S202, a buffer gallium nitride layer 20 is epitaxially grown on a sapphire substrate by a metal organic chemical vapor deposition (MOCVD) process on one side surface of the substrate 10. The buffer gallium nitride layer 20 is an unintentionally doped gallium nitride layer (u-GaN), and the thickness of the buffer gallium nitride layer 20 is 4 μm to 5 μm.

[0123] Step S203, epitaxially forming a P-type gallium nitride layer 30 on the surface of the buffer gallium nitride layer 20 facing away from the substrate, wherein the doping material of the P-type gallium nitride layer 30 is Mg, and the doping concentration is 10 17 cm -3 ~10 19 cm -3 The thickness of the P-type gallium nitride layer 30 is 150 nm to 200 nm.

[0124] Step S204 , epitaxially growing a gallium oxide film on a surface of the P-type gallium nitride layer 30 facing away from the buffer gallium nitride layer 20 by molecular beam epitaxy technology, wherein the thickness of the gallium oxide film is 90 nm to 100 nm.

[0125] Step S205, performing patterning photolithography and etching processes on the gallium oxide film to form a patterned gallium oxide layer 40; the top view of the gallium oxide layer 40 is rectangular; the length of the gallium oxide layer 40 is 800 μm to 1000 μm, and the width is 300 μm to 500 μm, such as Fig. 9 shown.

[0126] In the specific implementation, the sample is first cleaned and dried, then a photoresist is formed on the surface of the gallium oxide film, and the photoresist is etched to obtain a patterned photoresist corresponding to the gallium oxide layer; finally, the exposed gallium oxide film is etched using inductively coupled plasma etching technology, and the pattern is transferred to the gallium nitride layer, so that a mesa structure is formed on the device surface.

[0127] Step S206 , coating a photoresist on the surface of the P-type gallium nitride layer 30 , exposing the photoresist and then developing it to obtain a patterned photoresist corresponding to the second electrode 52 .

[0128] Step S207, Ni / Au is evaporated on the surface of the patterned photoresist by an electron beam evaporation coating system to form a second electrode 52; the second electrode 52 forms an electrical contact with the P-type gallium nitride layer 30; the second electrode 52 is a ring electrode; the second electrode 52 surrounds the side of the gallium oxide layer 40; the line width of the second electrode 52 is 10μm~20μm; the interval between the second electrode 52 and the gallium oxide layer 40 is 10μm~20μm; the thickness of Ni in the second electrode 52 is 20nm, and the thickness of Au is 50nm.

[0129] Step S207 , soaking the sample on which the second electrode is formed after evaporation and subjecting it to low-power ultrasound to remove the patterned photoresist and the redundant metal film layer.

[0130] In a specific implementation, since the photoresist can be dissolved by acetone, under the ultrasonic condition of the acetone agent, the photoresist and the metal film layer covering it will be separated from the sample surface.

[0131] Step S208, using a high temperature annealing furnace to perform rapid thermal annealing on the sample in an air environment, the annealing temperature is 550° C., and the annealing time is 10 minutes.

[0132] In a specific implementation, the rapid thermal annealing process can reduce the contact resistance of the second electrode.

[0133] Step S209 , forming a photoresist on the surface of the gallium oxide layer 40 facing away from the P-type gallium nitride layer 30 , and etching the photoresist to obtain a patterned photoresist corresponding to the interdigital electrodes.

[0134] Step S210, Ti / Au is evaporated on the surface of the patterned photoresist by an electron beam evaporation coating system to form interdigital electrodes; the interdigital electrodes include a first electrode 51 and a third electrode 53, and the first electrode 51 and the third electrode 53 are in electrical contact with the gallium oxide layer respectively; the thickness of Ti in the first electrode 51 and the third electrode 53 is 10 nm, and the thickness of Au is 50 nm.

[0135] Step S211 , the sample with interdigital electrodes formed after evaporation is immersed in acetone and subjected to low-power ultrasound to remove the patterned photoresist and the excess metal film layer.

[0136] In a specific implementation, since the photoresist can be dissolved by acetone, under the ultrasonic condition of the acetone agent, the photoresist and the metal film layer covering it will be separated from the sample surface.

[0137] Step S212, using a high temperature annealing furnace to perform rapid thermal annealing on the sample in an air environment, the annealing temperature is 400° C., the annealing time is 5 min, and the flow rate is 4 slm.

[0138] In a specific implementation, the rapid thermal annealing process can reduce the contact resistance between the first electrode 51 and the third electrode 53 .

[0139] In the description of this specification, the description with reference to the terms "this embodiment", "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless otherwise clearly and specifically defined. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0140] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0141] The above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described above, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the concept of the present invention. The scope of protection of the present invention is determined by the scope of the attached claims.

Claims

1. A tunable dual-band ultraviolet photodetector, characterized in that: The tunable dual-band ultraviolet photodetector comprises: substrate; A buffer gallium nitride layer, located on one side surface of the substrate; A P-type gallium nitride layer, located on a surface of the buffer gallium nitride layer facing away from the substrate; A gallium oxide layer, located on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer; A second electrode is located on a surface of the P-type gallium nitride layer at a side of the gallium oxide layer; the second electrode forms an electrical contact with the P-type gallium nitride layer; The interdigitated electrodes are located on a surface of the gallium oxide layer facing away from the P-type gallium nitride layer; the interdigitated electrodes include a first electrode and a third electrode, and the first electrode and the third electrode are respectively in electrical contact with the gallium oxide layer.

2. The tunable dual-band ultraviolet photodetector according to claim 1, characterized in that: The material of the second electrode is Ni / Au; The materials of the first electrode and the third electrode are Ti / Au.

3. The tunable dual-band ultraviolet photodetector according to claim 2, characterized in that: The thickness of Ni in the second electrode is 20 nm, and the thickness of Au is 50 nm; The thickness of Ti in the first electrode and the third electrode is 10 nm, and the thickness of Au is 50 nm.

4. The tunable dual-band ultraviolet photodetector according to claim 1, characterized in that: The second electrode is a ring electrode; The second electrode surrounds a side of the gallium oxide layer, and a gap exists between the annular electrode and the gallium oxide layer.

5. The tunable dual-band ultraviolet photodetector according to claim 4, characterized in that: The gallium oxide layer is rectangular in top view; The line width of the second electrode is 1 μm to 100 μm; The distance between the second electrode and the gallium oxide layer is 1 μm to 100 μm.

6. The tunable dual-band ultraviolet photodetector according to claim 1, characterized in that: The thickness of the gallium oxide layer is 90nm to 100nm; The doping material of the P-type gallium nitride layer is Mg, and the doping concentration is 10 17 cm -3 ~10 19 cm -3 ; The thickness of the P-type gallium nitride layer is 150nm to 200nm; The buffer gallium nitride layer is an unintentionally doped gallium nitride layer; The buffer gallium nitride layer has a thickness of 4 μm to 5 μm.

7. The tunable dual-band ultraviolet photodetector according to claim 1, characterized in that: The first electrode is a detection electrode; the third electrode is grounded; the potential that the second electrode is suitable for accessing is less than or equal to 0V; When the voltage between the first electrode and the third electrode is a first target voltage, the first electrode only detects ultraviolet light in a first wavelength band; When the voltage between the first electrode and the third electrode is a second target voltage, the first electrode only detects ultraviolet light in the second wavelength band; When the voltage between the first electrode and the third electrode is between the first target voltage and the second target voltage, the first electrode can detect ultraviolet light in the first wavelength band and the second wavelength band at the same time.

8. The tunable dual-band ultraviolet photodetector according to claim 7, characterized in that: The first waveband is 200nm to 260nm; the second waveband is 260nm to 360nm; The first target voltage is the second electrode potential minus 0.6V; the second target voltage is -0.3V to 0V.

9. A method for preparing a tunable dual-band ultraviolet photodetector, used for preparing the tunable dual-band ultraviolet photodetector as claimed in claim 1, characterized in that: providing a substrate; forming a buffer gallium nitride layer on a surface of one side of the substrate; forming a P-type gallium nitride layer on a surface of the buffer gallium nitride layer facing away from the substrate; forming a gallium oxide layer on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer; A second electrode is formed on the surface of the P-type gallium nitride layer at the side of the gallium oxide layer; the second electrode forms an electrical contact with the P-type gallium nitride layer; An interdigitated electrode is formed on a surface of the gallium oxide layer facing away from the P-type gallium nitride layer; the interdigitated electrode includes a first electrode and a third electrode, and the first electrode and the third electrode are respectively in electrical contact with the gallium oxide layer.

10. The method for preparing a tunable dual-band ultraviolet photodetector according to claim 9, characterized in that: The step of forming a gallium oxide layer on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer comprises: epitaxially growing a gallium oxide film on a surface of the P-type gallium nitride layer facing away from the buffer gallium nitride layer; Performing patterned photolithography and etching processes on the gallium oxide film to form a patterned gallium oxide layer; The step of forming a second electrode on the surface of the P-type gallium nitride layer at the side of the gallium oxide layer includes: Coating a photoresist on the surface of the P-type gallium nitride layer, exposing the photoresist and then developing the photoresist to obtain a patterned photoresist corresponding to the second electrode; Ni / Au is evaporated on the surface of the patterned photoresist to form a second electrode, and the patterned photoresist is removed.

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