GaN-based ultraviolet photoelectric detector based on bottom electrode control and preparation method thereof

Abstract

The invention relates to a GaN-based ultraviolet photoelectric detector based on bottom electrode control and a preparation method of the GaN-based ultraviolet photoelectric detector, and belongs to the field of photoelectric detectors. The bottom electrode is positioned on the upper surface of the substrate layer; the dielectric layer covers the upper surface of one side of the bottom electrode, and the upper surface of the other side of the bottom electrode is partially exposed; the GaN layer is located on the upper surface of the dielectric layer; the drain electrode and the source electrode are both arranged on the upper surface of the GaN layer, and the source electrode (6) is arranged close to one side of the exposed upper surface of the bottom electrode. According to the GaN-based ultraviolet photoelectric detector based on bottom electrode control, the dielectric layer is arranged between the bottom electrode and the GaN layer, the upper surface of the bottom electrode is partially exposed, the bottom electrode can be controlled based on positive and negative bias voltages, then an inversion layer is formed by using the control electric field effect of the bottom electrode, and on the premise that the transverse transport speed is taken into consideration, the GaN-based ultraviolet photoelectric detector based on bottom electrode control can be obtained. The effect of promoting the transport of carriers in the vertical direction is achieved, and the light current and the response speed are effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric detectors, and in particular relates to a GaN-based ultraviolet photoelectric detector based on bottom electrode control and a preparation method thereof. Background Art

[0002] Ultraviolet photodetectors are sensors that can convert ultraviolet light signals into electrical signals. They play an important role in military, environmental monitoring, flame monitoring, medical diagnosis, industrial detection and other fields. Wide-bandgap semiconductor material GaN has the superior characteristics of high electron mobility, high breakdown field strength, and high saturation electron velocity. Among them, the bandgap width of GaN-based ternary alloy AlxGa1-xN can continuously change in the range of 3.4 to 6.2eV with the change of Al component. In the common AlGaN / GaN / AlGaN structure, at the AlGaN / GaN heterojunction interface, due to the different bandgap widths of AlGaN and GaN, a band step difference will be formed. Since the lattice constant of AlGaN is greater than that of GaN, the AlGaN layer is subjected to tensile stress, resulting in piezoelectric polarization and spontaneous polarization pointing to the C-axis direction. After the two polarization effects cancel each other out at the heterojunction interface, a net positive polarization charge will be left at the AlGaN / GaN heterojunction interface, causing the energy band to bend at the heterojunction interface to form a two-dimensional potential well; the two-dimensional potential well restricts electrons to move in two dimensions only in a plane parallel to the heterojunction, forming a two-dimensional electron gas. Similarly, at the interface of GaN and AlGaN, there is also a band step difference and a net negative polarization charge, which will form a potential well that restricts the movement of holes parallel to the plane of the heterojunction, called a two-dimensional hole gas. Under the action of the polarization effect, the recombination of photogenerated carriers is suppressed, the lifetime of photogenerated carriers is extended, and they are easier to be captured by electrodes. In addition, the conductive channel formed by the two-dimensional potential well accelerates the drift of photogenerated carriers in the two-dimensional plane.

[0003] At present, vertical PIN photodetectors and planar MSM photodetectors are the most studied. Vertical PIN photodetectors complete the vertical transport of photogenerated carriers through the self-built electric field between the depletion layers at the junction, but the Al composition and the thickness of the intrinsic layer need to be adjusted to balance the light-dark current ratio and the response time, and the lateral diffusion of photogenerated carriers cannot be accelerated. Planar MSM photodetectors have a much shorter vertical transport distance than vertical PIN photodetectors because the absorption layer is located near the surface of the device. They have a simple structure, low parasitic capacitance, and can use two-dimensional electron gas to achieve rapid transport of photogenerated carriers in the plane direction, but they still face the problem of low absorption efficiency.

[0004] Therefore, there is a need for a photoelectric detector that can take into account both the lateral transport speed and the vertical transport effect and a preparation method thereof. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a GaN-based ultraviolet photodetector based on bottom electrode control and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] The present invention provides a GaN-based ultraviolet photodetector based on bottom electrode control, comprising: a substrate layer; a bottom electrode, located on the upper surface of the substrate layer; a dielectric layer, covering the upper surface of one side of the bottom electrode, with the upper surface of the other side of the bottom electrode partially exposed; a GaN layer, located on the upper surface of the dielectric layer; a drain electrode and a source electrode, both arranged on the upper surface of the GaN layer, wherein the source electrode is arranged close to the exposed upper surface side of the bottom electrode.

[0007] In one embodiment of the present invention, the material of the substrate layer includes: sapphire, Si or diamond.

[0008] In one embodiment of the present invention, the material of the bottom electrode includes: Ni / Au, Ni / Ag or Au.

[0009] In one embodiment of the present invention, the material of the dielectric layer includes: superlattice AlGaN, AlN, Al2O3, SiNx or SiO2.

[0010] In one embodiment of the present invention, the drain electrode (5) and the source electrode (6) both comprise: a Ti / Al / Ni / Au mixed metal layer or a Ni / Au mixed metal layer.

[0011] In one embodiment of the present invention, the GaN-based ultraviolet photodetector based on bottom electrode control also includes: an epitaxial structure, wherein the epitaxial structure includes: a temporary substrate layer, a buffer layer and a GaN layer arranged in sequence from top to bottom; the material of the buffer layer includes: AlN or GaN.

[0012] In one embodiment of the present invention, an AlGaN layer is provided between the dielectric layer and the GaN layer.

[0013] In one embodiment of the present invention, the GaN layer is a P-GaN layer, and an AlGaN layer is disposed on the upper surface of the P-GaN layer, and the drain electrode (5) and the source electrode (6) are both disposed on the upper surface of the AlGaN layer.

[0014] In one embodiment of the present invention, the content of Al component in the AlGaN layer is 0.21, and the acceptor doping concentration in the GaN layer is 5×10 18 cm -3 Up to 3×10 19 cm -3 , the donor doping concentration in the GaN layer is 1015 cm -3 Up to 10 16 cm -3 .

[0015] The present invention also provides a method for preparing a GaN-based ultraviolet photodetector based on bottom electrode control, comprising:

[0016] Growing a buffer layer on the temporary substrate layer, and growing a GaN layer on the surface of the buffer layer to obtain an epitaxial structure;

[0017] Growing a dielectric layer on the surface of the GaN layer of the epitaxial structure;

[0018] Prepare a substrate layer, and grow a metal layer on the upper surface of the dielectric layer and the upper surface of the substrate layer respectively;

[0019] Turning over the epitaxial structure, bonding the epitaxial structure to the substrate layer through the metal layer, and using the bonded metal layer as a bottom electrode;

[0020] Stripping off the temporary substrate layer, and etching off the buffer layer;

[0021] Using a photoresist as a mask, etching downward from the upper surface of one side of the GaN layer to the upper surface of the bottom electrode;

[0022] A photoresist is used as a mask, and a drain electrode and a source electrode are respectively grown on the upper surface of the GaN layer to obtain a GaN-based ultraviolet photodetector based on bottom electrode control.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The GaN-based ultraviolet photodetector based on bottom electrode control of the present invention has a dielectric layer arranged between the bottom electrode and the GaN layer, and the upper surface portion of the bottom electrode is exposed to the outside. The bottom electrode can be controlled based on positive and negative bias voltages and then an inversion layer can be formed by utilizing the controlled electric field of the bottom electrode. While taking into account the lateral transport speed, the vertical transport of carriers can be promoted, thereby effectively improving the photocurrent and response speed.

[0025] The GaN-based ultraviolet photodetector based on bottom electrode control of the present invention, when a negative bias is applied between the gate and the source, the bottom electrode surface will carry a large amount of negative charges, thereby attracting positive charges inside the GaN layer to move toward the bottom electrode surface; due to the blocking effect of the dielectric layer between the bottom electrode and the GaN layer, a large amount of positive charges will be accumulated at the interface between the dielectric layer and the GaN layer, thereby causing a large amount of negative charges to be accumulated on the side of the GaN layer away from the dielectric layer; when light is incident on the device surface to generate photogenerated carriers, based on the action of the electric field, the generated photogenerated electrons will enter the channel formed by the accumulation of negative charges, accelerate the transport process of the photogenerated electrons, and finally enter the channel formed by the accumulation of positive charges, thereby realizing the directional and rapid transport of the photogenerated carriers, reducing the recombination loss of the photogenerated carriers, and improving the photocurrent and response speed of the device; when a positive bias is applied, the photogenerated electrons will enter the channel where the positive charges are accumulated, and the photogenerated holes will enter the channel where the negative charges are accumulated and be consumed, so that the device is turned off, thereby realizing the switching state of the device being adjusted by the gate-controlled bias.

[0026] The GaN-based ultraviolet photodetector based on bottom electrode control of the present invention can form a high-mobility carrier channel of two-dimensional electron gas or two-dimensional hole gas inside the device, and further promotes the lateral transport process of photogenerated carriers through the high-mobility carrier channel, thereby suppressing the recombination of photogenerated carriers, improving the transport efficiency and collection efficiency of photogenerated carriers, and improving the sensitivity and response speed of the photodetector.

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of a GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention;

[0029] Figure 2 It is a schematic flow chart of a method for preparing a GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention;

[0030] Figure 3a-3h It is a schematic diagram of a process for preparing a GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention.

[0031] Figure 4 A schematic structural diagram of another GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention;

[0032] Figure 5A schematic structural diagram of another GaN-based ultraviolet photodetector based on bottom electrode control provided in an embodiment of the present invention.

[0033] Figure numerals: 1 - substrate layer; 2 - bottom electrode; 3 - dielectric layer; 4 - GaN layer; 5 - drain electrode; 6 - source electrode; 7 - epitaxial structure; 71 - temporary substrate layer; 72 - buffer layer; 8 - AlGaN layer. DETAILED DESCRIPTION

[0034] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of a GaN-based ultraviolet photodetector based on bottom electrode control and a preparation method thereof proposed in accordance with the present invention, in combination with the accompanying drawings and specific implementation methods.

[0035] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0036] Embodiment 1

[0037] The present invention provides a GaN-based ultraviolet photodetector based on bottom electrode control, such as Figure 1 As shown, Figure 1 The schematic diagram of the structure of a GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention. The device includes:

[0038] Substrate layer 1;

[0039] A bottom electrode 2, located on the upper surface of the substrate layer 1;

[0040] The dielectric layer 3 covers the upper surface of one side of the bottom electrode 2, and the upper surface of the other side of the bottom electrode 2 is partially exposed;

[0041] GaN layer 4, located on the upper surface of dielectric layer 3;

[0042] The drain electrode 5 and the source electrode 6 are both arranged on the upper surface of the GaN layer 4 , wherein the source electrode 6 is arranged close to the exposed upper surface side of the bottom electrode 2 .

[0043] Optionally, the material of the substrate layer 1 includes: sapphire, Si or diamond.

[0044] Preferably, the material of the substrate layer 1 is diamond. The substrate layer 1 prepared by using diamond material can better improve the heat dissipation capacity of the device structure and improve the reliability of the device.

[0045] Optionally, the material of the bottom electrode 2 includes: Ni / Au, Ni / Ag or Au.

[0046] Optionally, the material of the dielectric layer 3 includes: superlattice AlGaN, AlN, Al2O3, SiNx or SiO2.

[0047] Optionally, the drain electrode 5 and the source electrode 6 both include: a Ti / Al / Ni / Au mixed metal layer or a Ni / Au mixed metal layer.

[0048] It is understandable that the materials of the drain electrode 5 and the source electrode 6 can be selected according to the required barrier difference between the gold semiconductor contacts.

[0049] Exemplarily, the structures of the drain electrode 5 and the source electrode 6 include but are not limited to a symmetrical bidigital type or an asymmetrical bidigital type.

[0050] Preferably, both the drain electrode 5 and the source electrode 6 are of a double-finger structure to achieve a higher photoelectric conversion efficiency.

[0051] In this embodiment, the GaN-based ultraviolet photodetector based on bottom electrode control also includes: an epitaxial structure 7 for preparing a GaN layer 4. Specifically, the GaN layer 4 is first prepared on the epitaxial structure 7 and then bonded to the substrate layer 1 after subsequent flipping to achieve substrate replacement.

[0052] Specifically, the epitaxial structure 7 includes: a temporary substrate layer 71, a buffer layer 72 and a GaN layer 4 arranged in sequence from top to bottom; after the epitaxial structure 7 is prepared, a dielectric layer 3 is regrown on the GaN layer 4, and the dielectric layer 3 can be used for charge blocking regulated by the bottom electrode 2.

[0053] Optionally, the material of the buffer layer 72 includes: AlN or GaN.

[0054] like Figure 4 As shown, in an optional embodiment, after preparing the epitaxial structure 7 and before growing the dielectric layer 3, an AlGaN layer 8 can be set between the dielectric layer 3 and the GaN layer 4, and the device structure formed by growing the AlGaN layer 8 on the surface of the GaN layer 4 will contain a two-dimensional electron gas.

[0055] The principle is that an AlGaN layer 8 is inserted between the dielectric layer 3 and the GaN layer 4. Since the GaN layer 4 and the AlGaN layer 8 are in N-polar surface contact, 2DEG (two-dimensional electron gas) is formed between the GaN layer 4 and the AlGaN layer 8. When light is incident on the surface of the GaN layer 4 to form photogenerated carriers, the generated electrons will promote their lateral transport process under the action of the two-dimensional electron gas.

[0056] like Figure 5As shown, in an optional embodiment, during the preparation of the epitaxial structure 7, the GaN layer 4 can also be set as a P-GaN layer, and after the epitaxial structure 7 is bonded to the substrate layer 1, an AlGaN layer 8 is set on the upper surface of the P-GaN layer, and finally the drain electrode 5 and the source electrode 6 are both set on the upper surface of the AlGaN layer 8. The device structure finally formed will contain two-dimensional hole gas.

[0057] Optionally, the content of Al component in the AlGaN layer 8 is 0.21, and the acceptor doping concentration in the GaN layer 4 is 5×10 18 cm -3 Up to 3×10 19 cm -3 , the donor doping concentration in the GaN layer 4 is 10 15 cm -3 Up to 10 16 cm -3 .

[0058] The principle is that the GaN layer 4 is set to P-GaN, and the AlGaN layer 8 is inserted between the GaN layer 4 and the drain electrode 5 and the source electrode 6. The GaN layer 4 and the AlGaN layer 8 are in Ga polar surface contact, and 2DHG (two-dimensional hole gas) is formed between the P-GaN and AlGaN layers 8. When light is incident on the surface of the GaN layer 4 to form photogenerated carriers, the generated holes will promote their lateral transport process under the action of the two-dimensional hole gas.

[0059] It is worth noting that due to the existence of two-dimensional electron gas or two-dimensional hole gas inside the device, the corresponding carriers (electrons or holes) in the GaN layer 4 will be confined to the two-dimensional electron gas or two-dimensional hole gas interface due to the potential well effect. The conductive channel formed by the potential well effect and the high carrier mobility of the two-dimensional electron gas or two-dimensional hole gas itself improve the transport speed of the device in the horizontal direction, and it is less likely to recombine with other carriers, so that the device has a fast response speed in the horizontal direction and high light absorption efficiency.

[0060] The GaN-based ultraviolet photodetector based on bottom electrode control of the present invention has a dielectric layer arranged between the bottom electrode and the GaN layer, and the upper surface portion of the bottom electrode is exposed to the outside. The bottom electrode can be controlled based on positive and negative bias voltages and then an inversion layer can be formed by utilizing the controlled electric field of the bottom electrode. While taking into account the lateral transport speed, the vertical transport of carriers can be promoted, thereby effectively improving the photocurrent and response speed.

[0061] The GaN-based ultraviolet photodetector based on bottom electrode control of the present invention, when a negative bias is applied between the gate and the source, the bottom electrode surface will carry a large amount of negative charges, thereby attracting positive charges inside the GaN layer to move toward the bottom electrode surface; due to the blocking effect of the dielectric layer between the bottom electrode and the GaN layer, a large amount of positive charges will be accumulated at the interface between the dielectric layer and the GaN layer, thereby causing a large amount of negative charges to be accumulated on the side of the GaN layer away from the dielectric layer; when light is incident on the device surface to generate photogenerated carriers, based on the action of the electric field, the generated photogenerated electrons will enter the channel formed by the accumulation of negative charges, accelerate the transport process of the photogenerated electrons, and finally enter the channel formed by the accumulation of positive charges, thereby realizing the directional and rapid transport of the photogenerated carriers, reducing the recombination loss of the photogenerated carriers, and improving the photocurrent and response speed of the device; when a positive bias is applied, the photogenerated electrons will enter the channel where the positive charges are accumulated, and the photogenerated holes will enter the channel where the negative charges are accumulated and be consumed, so that the device is turned off, thereby realizing the switching state of the device being adjusted by the gate-controlled bias.

[0062] The GaN-based ultraviolet photodetector based on bottom electrode control of the present invention can form a high-mobility carrier channel of two-dimensional electron gas or two-dimensional hole gas inside the device, and further promotes the lateral transport process of photogenerated carriers through the high-mobility carrier channel, thereby suppressing the recombination of photogenerated carriers, improving the transport efficiency and collection efficiency of photogenerated carriers, and improving the sensitivity and response speed of the photodetector.

[0063] Embodiment 2

[0064] Based on the same inventive concept, the present invention also provides a method for preparing a GaN-based ultraviolet photodetector based on bottom electrode control. The preparation method provided in this embodiment is described in detail below in conjunction with the accompanying drawings. Figure 2 and Figure 3a-3h , Figure 2 It is a schematic flow chart of a method for preparing a GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention; Figure 3a-3h It is a schematic diagram of a process for preparing a GaN-based ultraviolet photodetector based on bottom electrode control provided by an embodiment of the present invention.

[0065] The method for preparing the GaN-based ultraviolet photodetector based on bottom electrode control of this embodiment includes:

[0066] Step 1: growing a buffer layer on a temporary substrate layer, growing a GaN layer on the surface of the buffer layer, and growing a dielectric layer on the surface of the GaN layer to obtain an epitaxial structure;

[0067] Specifically, a temporary substrate layer is prepared, and a buffer layer is grown on the prepared temporary substrate layer. The buffer layer is used to alleviate the stress and defect dislocation problems caused by the mismatch between the lattice and thermal expansion coefficient between the substrate layer and the GaN layer. A GaN layer is grown on the buffer layer for the transport process of photogenerated carriers to obtain an epitaxial structure, such as Figure 3a shown.

[0068] Exemplarily, the preparation and growth process of the buffer layer includes, but is not limited to, a MOCVD process (metal organic chemical vapor deposition), an ALD process (atomic layer deposition), and a PECVD process (plasma enhanced chemical vapor deposition).

[0069] Step 2: growing a dielectric layer on the surface of the GaN layer of the epitaxial structure;

[0070] Specifically, a dielectric layer is grown on the surface of the GaN layer of the epitaxial structure, such as Figure 3b As shown, the dielectric layer is used to achieve the functions of electrical isolation and electric field regulation.

[0071] Step 3: preparing a substrate layer, and growing a metal layer on the upper surface of the dielectric layer and the upper surface of the substrate layer respectively;

[0072] Specifically, the metal layer grown on the dielectric layer and the metal layer grown on the substrate layer can be used in the subsequent bonding process. At the same time, the metal layer grown on the epitaxial structure can also be used as the bottom electrode of the device structure. Figure 3c As shown; the metal layer grown on the substrate layer, such as Figure 3d shown.

[0073] Step 4: flip the epitaxial structure, connect the epitaxial structure to the substrate layer through metal layer bonding, and use the bonded metal layer as the bottom electrode;

[0074] The device structure after bonding, such as Figure 3e shown.

[0075] Step 5: Peel off the temporary substrate layer and etch off the buffer layer;

[0076] Specifically, after the temporary substrate layer is stripped off, the buffer layer is completely etched off, such as Figure 3f As shown, etching away the buffer layer facilitates the subsequent growth of metal on the surface of the GaN layer.

[0077] Exemplarily, the etching process includes, but is not limited to, an ICP process (inductively coupled plasma etching) or a RIE process (reactive ion etching).

[0078] Step 6: Using a photoresist as a mask, etching downward from the upper surface of one side of the GaN layer to the upper surface of the bottom electrode;

[0079] Specifically, the surface of the GaN layer is selectively etched to the surface of the bottom electrode to expose the bottom electrode, such as Figure 3g As shown, it is convenient to subsequently apply a bias voltage between the bottom electrode and the source electrode to generate a control electric field;

[0080] Step 7: Using photoresist as a mask, grow a drain electrode and a source electrode on the upper surface of the GaN layer respectively to obtain a GaN-based ultraviolet photodetector controlled by a bottom electrode.

[0081] Specifically, a photoresist is used as a mask to selectively grow a source electrode and a drain electrode on the surface of the GaN layer, such as Figure 3h As shown, the source electrode and the drain electrode are used to collect photogenerated carriers and to realize directional transport of current when a bias is applied to the bottom electrode. Thus, the preparation of GaN-based ultraviolet photodetector based on bottom electrode control is completed.

[0082] It should be noted that the MOCVD process, ALD process, PECVD process, bonding process, ICP process, RIE process, photolithography process, etching process, electron beam evaporation or magnetron sputtering process used in the process of preparing the GaN-based ultraviolet photodetector based on bottom electrode control in this embodiment are all existing mature processes, and the corresponding parameter settings can be implemented by referring to the existing relevant technologies.

[0083] The preparation method provided in this embodiment can be used to prepare the GaN-based ultraviolet photodetector based on bottom electrode control of embodiment 1, and therefore has similar beneficial effects as the device embodiment of embodiment 1. For technical details not disclosed in the preparation method embodiment of the present invention, please refer to the description of the device embodiment for understanding.

[0084] Embodiment 3

[0085] In this embodiment, a sapphire substrate is used as a growth substrate, and a GaN-based ultraviolet photodetector based on bottom electrode control is prepared by the preparation method of the GaN-based ultraviolet photodetector based on bottom electrode control in the second embodiment. The structure of the prepared device is as follows: Figure 1 As shown, the specific preparation method is as follows:

[0086] S1: An AlN / GaN superlattice buffer layer is grown on a sapphire substrate using a MOCVD process. The thickness of the buffer layer is 0.8 μm. An unintentionally doped GaN layer is grown on the surface of the buffer layer using a MOCVD process to obtain an epitaxial structure. The intrinsic n-type carrier concentration of the GaN layer is 10 15 Up to 10 16 cm -3 .

[0087] S2: A SiO2 dielectric layer with a thickness of 10 to 30 nm is grown on the surface of the GaN layer using PECVD. The growth temperature is 100 to 350°C, the cavity pressure is 120 Pa, the microwave power is 2500 to 3200 W, the precursor gases are SiH4 and NH3, and the carrier gas is Ar.

[0088] S3: growing a Ni / Au metal layer with a thickness of 30 / 100 nm on the dielectric layer by electron beam evaporation, and growing a Ni / Au metal layer with a thickness of 30 / 100 nm on another sapphire substrate by electron beam evaporation.

[0089] S4: Flip the epitaxial structure and use a bonding machine to bond the gold surface parts of the two samples to obtain a new bonded structure.

[0090] S5: Use the stripping process to achieve temporary substrate stripping, and use the inductively coupled plasma etching process to etch the buffer layer of the new structure so that the buffer layer is completely removed. The temperature is 10 to 100°C, the chamber pressure is 0.1 to 1Pa, the etching power is 100 to 500W, the RF power is 15 to 75W, and the etching gas is a mixture of BCl3 and Cl2.

[0091] S6: Use photoresist as a mask to photolithography patterns on the surface of the GaN layer, and use inductively coupled plasma etching process and reactive ion etching process to perform two-step selective etching to expose the bottom electrode on one side of the device structure, and then remove excess photoresist. The temperature of reactive ion etching is 40 to 60°C, the chamber pressure is 30 to 50mTorr, the RF power is 200W, and the etching gas is a mixture of CF4 and CHF3.

[0092] S7: Photolithography of the interdigital electrode pattern was performed on the surface of the GaN layer. Ti / Al / Ni / Au=20nm / 130nm / 50nm / 45nm was grown using electron beam evaporation. Excess photoresist was removed and annealing was performed. Rapid thermal annealing was performed at 850°C in a nitrogen atmosphere for 35s to form an ohmic contact. The preparation of the GaN-based ultraviolet photodetector based on bottom electrode control was completed.

[0093] Embodiment 4

[0094] In this embodiment, Si is used as a growth substrate, and the preparation method of the GaN-based ultraviolet photodetector based on bottom electrode control in the second embodiment is used to prepare a GaN-based ultraviolet photodetector based on bottom electrode control. The structure of the prepared device is as follows: Figure 5 As shown, the specific preparation method is as follows:

[0095] S1: A low-temperature AlN buffer layer and a high-temperature AlN buffer layer were grown on a Si substrate using MOCVD technology, with thicknesses of 10 nm and 200 nm respectively. A P-GaN layer was grown on the surface of the buffer layer using MOCVD technology. P-type heavy doping was achieved by Mg diffusion method, and the internal p-type carrier concentration was 5×10 18 Up to 3×10 19 cm -3 .

[0096] S2: Using MOCVD to grow an AlGaN layer on the surface of the P-GaN layer, the Al composition is 0.21 and the thickness is 20 nm.

[0097] S3: A SiNx dielectric layer is grown on the surface of the GaN layer using PECVD with a thickness of 10 to 30 nm, a growth temperature of 100 to 350°C, a cavity pressure of 120 Pa, a microwave power of 2500 to 3200 W, precursor gases of SiH4 and NH3, and a carrier gas of Ar.

[0098] S4: A Ni / Au metal layer with a thickness of 30 / 100 nm is grown on the dielectric layer by electron beam evaporation; and a Ni / Au metal layer with a thickness of 30 / 100 nm is grown on another Si substrate by electron beam evaporation.

[0099] S5: Flip the epitaxial structure and use a bonding machine to bond the gold surface parts of the two samples to obtain a new bonded structure.

[0100] S6: Use the stripping process to achieve temporary substrate stripping, and use the inductively coupled plasma etching process to etch the buffer layer of the new structure so that the buffer layer is completely removed. The temperature is 10 to 100°C, the chamber pressure is 0.1 to 1Pa, the etching power is 100 to 500W, the RF power is 15 to 75W, and the etching gas is a mixture of BCl3 and Cl2.

[0101] S7: Use photoresist as a mask to photolithography patterns on the surface of the GaN layer, and use inductively coupled plasma etching process and reactive ion etching process to perform two-step selective etching to expose the bottom electrode on one side of the device structure, and then remove excess photoresist. The temperature of reactive ion etching is 40 to 60°C, the chamber pressure is 30 to 50mTorr, the RF power is 200W, and the etching gas is a mixture of CF4 and CHF3.

[0102] S8: Photolithography of the interdigital electrode pattern is performed on the surface of the GaN layer, and Ti / Al / Ni / Au=20nm / 130nm / 50nm / 45nm is grown using electron beam evaporation. Excess photoresist is removed, and the preparation of the GaN-based ultraviolet photodetector based on bottom electrode control is completed.

[0103] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant is intended to cover non-exclusive inclusion, so that the article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the article or device including the elements. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The orientation or position relationship indicated by "up", "down", "left", "right", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0104] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A GaN-based ultraviolet photodetector based on bottom electrode control, characterized in that: include: A substrate layer (1); A bottom electrode (2) located on the upper surface of the substrate layer (1); a dielectric layer (3) covering the upper surface of one side of the bottom electrode (2), with the upper surface of the other side of the bottom electrode (2) partially exposed; A GaN layer (4) located on the upper surface of the dielectric layer (3); The drain electrode (5) and the source electrode (6) are both arranged on the upper surface of the GaN layer (4), wherein the source electrode (6) is arranged close to the exposed upper surface side of the bottom electrode (2).

2. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: The material of the substrate layer (1) includes: sapphire, Si or diamond.

3. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: The material of the bottom electrode (2) includes: Ni / Au, Ni / Ag or Au.

4. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: The material of the dielectric layer (3) includes: superlattice AlGaN, AlN, Al2O3, SiNx or SiO2.

5. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: The drain electrode (5) and the source electrode (6) both comprise a Ti / Al / Ni / Au mixed metal layer or a Ni / Au mixed metal layer.

6. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: Also includes: Epitaxial structure (7), wherein The epitaxial structure (7) comprises: a temporary substrate layer (71), a buffer layer (72) and a GaN layer (4) arranged in sequence from top to bottom; the material of the buffer layer (72) comprises: AlN or GaN.

7. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: An AlGaN layer (8) is provided between the dielectric layer (3) and the GaN layer (4).

8. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 1, characterized in that: The GaN layer (4) is a P-GaN layer, and an AlGaN layer (8) is provided on the upper surface of the P-GaN layer; the drain electrode (5) and the source electrode (6) are both provided on the upper surface of the AlGaN layer (8).

9. The GaN-based ultraviolet photodetector based on bottom electrode control according to claim 8, characterized in that: The Al content of the AlGaN layer (8) is 0.21, and the acceptor doping concentration of the GaN layer (4) is 5×10 18 cm -3 Up to 3×10 19 cm -3 The donor doping concentration in the GaN layer (4) is 10 15 cm -3 Up to 10 16 cm -3 .

10. A method for preparing a GaN-based ultraviolet photodetector based on bottom electrode control, characterized in that: include: Growing a buffer layer on the temporary substrate layer, and growing a GaN layer on the surface of the buffer layer to obtain an epitaxial structure; Growing a dielectric layer on the surface of the GaN layer of the epitaxial structure; Prepare a substrate layer, and grow a metal layer on the upper surface of the dielectric layer and the upper surface of the substrate layer respectively; Turning over the epitaxial structure, bonding the epitaxial structure to the substrate layer through the metal layer, and using the bonded metal layer as a bottom electrode; Stripping off the temporary substrate layer, and etching off the buffer layer; Using a photoresist as a mask, etching downward from the upper surface of one side of the GaN layer to the upper surface of the bottom electrode; A photoresist is used as a mask, and a drain electrode and a source electrode are respectively grown on the upper surface of the GaN layer to obtain a GaN-based ultraviolet photodetector based on bottom electrode control.

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