Ultraviolet photoelectric detector and preparation method thereof

Abstract

The invention discloses an ultraviolet photoelectric detector and a preparation method thereof, and relates to the field of semiconductor optoelectronic devices. The ultraviolet photoelectric detector comprises an epitaxial layer, a channel layer, a barrier layer, a dielectric layer, a negative electrode and a positive electrode, wherein the epitaxial layer, the channel layer and the barrier layer are stacked from bottom to top; the channel layer and the barrier layer form a transparent electrode; the positive electrode is arranged on the epitaxial layer, and the positive electrode and the transparent electrode are arranged in a mutually-crossed interdigital distribution mode; the negative electrode is arranged on the barrier layer; and the dielectric layer is positioned on the channel layer to form a surrounding structure for the interdigital part of the barrier layer so as to isolate the positive electrode from the negative electrode. According to the ultraviolet photoelectric detector, the metal interdigitals and the transparent interdigitals are alternately arranged, the single photoetching electrode distance can be enlarged, the metal stripping difficulty is reduced, the dielectric layer is used for achieving the isolation effect between the negative electrode and the positive electrode, short circuit of the negative electrode and the positive electrode is prevented, and therefore the dark current of the ultraviolet photoelectric detector is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronic devices, and in particular relates to an ultraviolet photodetector and a preparation method thereof. Background Art

[0002] When light is incident, the thin films formed by materials with different refractive indices produce some special optical properties. Specifically, each material will show unique optical properties for light of different wavelengths, and different material parameters will also produce different filtering effects. Therefore, by selecting a suitable dielectric film and adjusting the material parameters of the dielectric film, the detector can achieve selective absorption of incident light of a specific wavelength. At the same time, in the preparation process of the detector, the etching process can block the two-dimensional electron gas and reduce the dark current, but it will inevitably introduce some defects and unstable surface states on the surface of the material, which will increase the recombination of photogenerated carriers.

[0003] GaN HEMT structure detectors have unique advantages. Due to the presence of two-dimensional electron gas, highly responsive ultraviolet detectors can be produced. However, if the responsiveness of this detector is to be further improved, it depends largely on the reduction of the electrode spacing. The reduction of the electrode spacing can enhance the electric field strength and improve the carrier collection efficiency, thereby improving the responsiveness of the detector. However, due to the limitations of the current process level, short circuits are very easy to form in the process of reducing the electrode spacing. This is because as the electrode spacing continues to decrease, the precision requirements in the manufacturing process become extremely high, and any slight process deviation may cause the distance between the electrodes to be too close, thereby causing a short circuit. This process challenge makes it a difficult problem to be solved in actual production, both to pursue higher responsiveness and to avoid the occurrence of short circuit problems. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides an ultraviolet photoelectric detector and a method for preparing the same. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0005] The present invention provides an ultraviolet photodetector, comprising: an epitaxial layer, a channel layer, a barrier layer, a dielectric layer, a cathode electrode and an anode electrode; wherein:

[0006] The epitaxial layer, the channel layer and the barrier layer are stacked from bottom to top;

[0007] The channel layer and the barrier layer form a transparent electrode;

[0008] The anode electrode is disposed on the epitaxial layer, and the anode electrode and the transparent electrode are arranged in a mutually interdigitated distribution manner;

[0009] The cathode electrode is disposed on the barrier layer;

[0010] The dielectric layer is located on the channel layer to form a surrounding structure for the interdigitated portion of the barrier layer, so as to isolate the anode electrode from the cathode electrode.

[0011] In one embodiment of the present invention, the material of the channel layer is unintentionally doped GaN or Al X Ga (1-X) N, where X is between 20% and 50%.

[0012] In one embodiment of the present invention, the channel layer includes a first channel portion and a second channel portion that are connected, the first channel portion is located on one side of the upper surface of the epitaxial layer, and the second channel portion includes a plurality of parallel strip channel layers to form a finger portion, and one end of each of the strip channel layers is connected to the first channel portion.

[0013] In one embodiment of the present invention, the barrier layer includes a first barrier portion and a second barrier portion that are connected, the first barrier portion is located on the upper surface of the first channel portion, the second barrier portion includes a plurality of parallel strip barrier layers forming a finger portion, one end of each of the strip barrier layers is connected to the first barrier portion, and the strip barrier layers are located on the upper surface of the corresponding strip channel layer.

[0014] In one embodiment of the present invention, the cathode electrode is located on an upper surface of the first potential barrier portion.

[0015] In one embodiment of the present invention, the material of the dielectric layer is silicon nitride, silicon oxide, aluminum oxide, zirconium oxide or hafnium oxide.

[0016] In one embodiment of the present invention, the thickness of the dielectric layer is 10 nm to 200 nm.

[0017] The present invention provides a method for preparing an ultraviolet photoelectric detector, which is applicable to the ultraviolet photoelectric detector described in any one of the above embodiments, and the preparation method comprises:

[0018] Step 1: preparing an epitaxial wafer, wherein the epitaxial wafer comprises an epitaxial layer, an initial channel layer and an initial barrier layer stacked in sequence from bottom to top;

[0019] Step 2: etching the initial channel layer and the initial barrier layer to form a channel layer and a barrier layer, wherein the channel layer and the barrier layer form a transparent electrode, and the transparent electrode is distributed in an interdigitated shape;

[0020] Step 3: preparing a dielectric layer on the channel layer, wherein the dielectric layer forms a surrounding structure for the interdigitated portion of the barrier layer;

[0021] Step 4: preparing a cathode electrode on the barrier layer, and preparing an anode electrode on the epitaxial layer, wherein the anode electrode and the transparent electrode are arranged in a cross-finger distribution manner.

[0022] In one embodiment of the present invention, step 3 comprises:

[0023] Step 3.1: preparing an initial dielectric layer on the surface of the device on which the transparent electrode is formed;

[0024] Step 3.2: Etching the initial dielectric layer to obtain a dielectric layer that is located on the channel layer and forms a surrounding structure for the interdigitated portion of the barrier layer.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The ultraviolet photodetector of the present invention comprises an epitaxial layer, a channel layer, a barrier layer, a dielectric layer, a cathode electrode and an anode electrode; wherein the epitaxial layer, the channel layer and the barrier layer are stacked from bottom to top; the channel layer and the barrier layer form a transparent electrode; the anode electrode is arranged on the epitaxial layer, and the anode electrode and the transparent electrode are arranged in a mutually crossed finger-shaped distribution; the cathode electrode is arranged on the barrier layer; the dielectric layer is located on the channel layer to form a surrounding structure for the finger portion of the barrier layer to isolate the anode electrode from the cathode electrode. In the present invention, the alternating arrangement of metal fingers and transparent fingers can expand the electrode spacing of a single photolithography, reduce the difficulty of metal stripping, and utilize the dielectric layer between the cathode electrode and the anode electrode to achieve an isolation effect to prevent the anode and cathode electrodes from short-circuiting, thereby reducing the dark current of the ultraviolet photodetector;

[0027] 2. The ultraviolet photodetector of the present invention can achieve selective detection of light by replacing the dielectric layer or adjusting the material of the dielectric layer and adjusting the filtering characteristics of the dielectric layer. At the same time, the dielectric layer can also serve as a passivation material to reduce the surface state introduced by etching and repair etching damage, thereby reducing the recombination of photogenerated carriers and improving quantum efficiency.

[0028] 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

[0029] Figure 1 is a schematic diagram of the side structure of an ultraviolet photoelectric detector provided by an embodiment of the present invention;

[0030] Figure 2 is a top view of an ultraviolet photodetector provided by an embodiment of the present invention;

[0031] Figure 3is a flow chart of a method for preparing an ultraviolet photoelectric detector provided by an embodiment of the present invention;

[0032] Figure 4 It is a process diagram of the preparation process of an ultraviolet photoelectric detector provided in an embodiment of the present invention.

[0033] Icon: 1-epitaxial layer; 2-channel layer; 3-barrier layer; 4-dielectric layer; 5-cathode; 6-anode. 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, an ultraviolet photoelectric detector and a preparation method thereof proposed in accordance with the present invention are described in detail below in conjunction 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] In the first aspect, an embodiment of the present invention provides an ultraviolet photoelectric detector, please refer to Figure 1 and Figure 2 , Figure 1 is a schematic diagram of the side structure of an ultraviolet photoelectric detector provided by an embodiment of the present invention; Figure 2 It is a top view of an ultraviolet photodetector provided by an embodiment of the present invention.

[0037] The ultraviolet photodetector of this embodiment includes: an epitaxial layer 1, a channel layer 2, a barrier layer 3, a dielectric layer 4, a cathode electrode 5 and an anode electrode 6. The epitaxial layer 1, the channel layer 2 and the barrier layer 3 are stacked from bottom to top; the channel layer 2 and the barrier layer 3 form a transparent electrode; the anode electrode 6 is arranged on the epitaxial layer 1, and the anode electrode 6 and the transparent electrode are arranged in a cross-finger distribution; the cathode electrode 5 is arranged on the barrier layer 3; the dielectric layer 4 is located on the channel layer 2 to form a surrounding structure for the interdigital portion of the barrier layer 3 to isolate the anode electrode 6 from the cathode electrode 5.

[0038] In an optional embodiment, the epitaxial layer 1 may be an AlGaN epitaxial layer or a GaN epitaxial layer.

[0039] In an optional embodiment, the material of the channel layer 2 is unintentionally doped GaN or Al X Ga (1-X) N, where X is between 20% and 50%.

[0040] In an optional embodiment, the material of the barrier layer 3 may be AlGaN.

[0041] In an optional embodiment, the channel layer 2 includes a first channel portion and a second channel portion that are connected, the first channel portion is located on one side of the upper surface of the epitaxial layer, and the second channel portion includes a plurality of parallel strip channel layers to form a finger portion, and one end of the strip channel layers is connected to the first channel portion.

[0042] In an optional embodiment, the barrier layer 3 includes a first barrier portion and a second barrier portion connected to each other, the first barrier portion is located on the upper surface of the first channel portion, and the second barrier portion includes a plurality of parallel strip barrier layers forming a forked finger portion, one end of each strip barrier layer is connected to the first barrier portion, and the strip barrier layers are located on the upper surface of the corresponding strip channel layer.

[0043] In this embodiment, the cathode electrode 5 is located on the upper surface of the first barrier portion. It should be noted that the width and length of the barrier layer 3 are both smaller than the width and length of the channel layer 2 .

[0044] In an optional embodiment, the material of the dielectric layer 4 is silicon nitride (SiN X ), silicon oxide (SiO2), aluminum oxide (Al2O3), zirconium oxide (Tm2O3)) or hafnium oxide (HfO2).

[0045] In this embodiment, the selective detection of light can be achieved by replacing the dielectric layer 4 or adjusting the material of the dielectric layer 4 to adjust the filtering characteristics of the dielectric layer.

[0046] In an optional embodiment, the thickness of the dielectric layer 4 is 10 nm to 200 nm.

[0047] For photodetectors with dual metal interdigital electrodes, reducing the electrode spacing makes the non-equilibrium carriers generated by light injection closer to the electrodes, which can effectively reduce the recombination of photogenerated carriers during the diffusion process and increase the external quantum efficiency. When the electrode spacing is reduced to the nm level, the metal is very likely to remain in the interdigital gaps and is not easy to peel off. In the ultraviolet photodetector of the embodiment of the present invention, metal interdigital fingers and transparent interdigital fingers are arranged alternately. Due to the asymmetric electrode structure, that is, the transparent electrode is in the middle of the metal electrode on the single side, the electrode spacing of a single photolithography can be expanded. Therefore, while reducing the electrode spacing, the difficulty of metal peeling is reduced.

[0048] Since metal is very likely to remain in the interdigital gaps, the residual metal will short-circuit the cathode and anode, increasing the dark current of the device. In the ultraviolet photodetector of the embodiment of the present invention, a dielectric layer is introduced to fill the interdigital gaps, which plays an isolation effect between the cathode and anode electrodes, preventing the cathode and anode electrodes from short-circuiting, thereby reducing the dark current of the ultraviolet photodetector. In addition, the dielectric layer of the present invention can also be used as a passivation material to reduce the surface state introduced by etching, repair etching damage, thereby reducing the recombination of photogenerated carriers and improving quantum efficiency.

[0049] In a second aspect, an embodiment of the present invention provides a method for preparing an ultraviolet photoelectric detector, which is applicable to the ultraviolet photoelectric detector provided in the first aspect. Figure 3 , Figure 3 FIG. 1 is a flow chart of a method for preparing an ultraviolet photoelectric detector provided by an embodiment of the present invention. Figure 3 As shown, the method for preparing the ultraviolet photodetector of this embodiment may include the following steps:

[0050] Step 1: Prepare an epitaxial wafer, which includes an epitaxial layer, an initial channel layer and an initial barrier layer stacked in sequence from bottom to top.

[0051] The epitaxial layer may be an AlGaN epitaxial layer or a GaN epitaxial layer, and the material of the channel layer may be an unintentionally doped GaN or Al X Ga (1-X) N, wherein X is between 20% and 50%, and the material of the barrier layer may be AlGaN.

[0052] Optionally, the epitaxial layer, the initial channel layer and the initial barrier layer may be prepared by using a metal organic chemical vapor deposition (MOCVD) technique, a molecular beam epitaxy (MBE) technique or a hydride vapor phase epitaxy (HVPE) technique.

[0053] Step 2: Etching the initial channel layer and the initial barrier layer to form a channel layer and a barrier layer, wherein the channel layer and the barrier layer form a transparent electrode, and the transparent electrode is distributed in an interdigitated shape.

[0054] In this embodiment, the channel layer includes a first channel portion and a second channel portion connected, the first channel portion is located on one side of the upper surface of the epitaxial layer, the second channel portion includes a plurality of parallel strip channel layers forming a finger portion, one end of each strip channel layer is connected to the first channel portion. The barrier layer includes a first barrier portion and a second barrier portion connected, the first barrier portion is located on the upper surface of the first channel portion, the second barrier portion includes a plurality of parallel strip barrier layers forming a finger portion, one end of each strip barrier layer is connected to the first barrier portion, and the strip barrier layer is located on the upper surface of the corresponding strip channel layer.

[0055] Optionally, the initial channel layer and the initial barrier layer may be etched by inductively coupled plasma etching, wet etching or dry etching to form the channel layer and the barrier layer.

[0056] Step 3: Prepare a dielectric layer on the channel layer, and the dielectric layer forms a surrounding structure for the interdigitated portion of the barrier layer.

[0057] Optionally, step 3 includes:

[0058] Step 3.1: preparing an initial dielectric layer on the surface of the device on which the transparent electrode is formed;

[0059] Optionally, the initial dielectric layer may be prepared by using plasma enhanced chemical vapor deposition (PECVD), magnetron sputtering, ion beam evaporation, physical vapor deposition (PVD) or atomic layer deposition (ALD) technology.

[0060] Step 3.2: Etch the initial dielectric layer to obtain a dielectric layer that is located on the channel layer and forms a surrounding structure for the interdigitated portion of the barrier layer.

[0061] Optionally, the initial dielectric layer may be etched by using reactive ion etching (RIE), wet etching or inductively coupled plasma etching (ICP).

[0062] In this embodiment, the material of the dielectric layer can be silicon nitride, silicon oxide, aluminum oxide, zirconium oxide or hafnium oxide. The thickness of the dielectric layer is 10nm to 200nm. Selective detection of light can be achieved by replacing the dielectric layer 4 or adjusting the material of the dielectric layer and adjusting the filtering characteristics of the dielectric layer.

[0063] Step 4: Prepare a cathode electrode on the barrier layer, and prepare an anode electrode on the epitaxial layer, and the anode electrode and the transparent electrode are arranged in a cross-finger distribution manner.

[0064] Optionally, electron beam evaporation coating technology can be used to evaporate metal on the barrier layer and the epitaxial layer to form a cathode electrode and an anode electrode.

[0065] The preparation method of the ultraviolet photoelectric detector of the embodiment of the present invention is simple, low-cost and suitable for large-scale production.

[0066] Further, the specific process of the preparation method of the ultraviolet photoelectric detector of the present invention is described with a specific embodiment, see Figure 4 , Figure 4 FIG. 1 is a process diagram of a preparation process of an ultraviolet photoelectric detector provided by an embodiment of the present invention. Figure 4 As shown, the method for preparing the ultraviolet photodetector of this embodiment includes:

[0067] S1: Select a sapphire substrate as a wafer substrate, and use hydride vapor phase epitaxy technology to sequentially epitaxially grow an AlGaN layer, an unintentionally doped GaN layer, and an AlGaN layer as an epitaxial layer 1, an initial channel layer, and an initial barrier layer on the wafer substrate;

[0068] S2: etching the initial channel layer and the initial barrier layer using an inductively coupled plasma etching process to form a channel layer 2 and a barrier layer 3;

[0069] The channel layer 2 includes a first channel portion and a second channel portion connected, the second channel portion is arranged perpendicularly to the first channel portion, and the second channel portion includes a plurality of parallel strip-shaped channel layers forming a finger portion. The barrier layer 3 includes a first barrier portion and a second barrier portion connected, the second barrier portion is arranged perpendicularly to the first barrier portion, and the second barrier portion includes a plurality of parallel strip-shaped barrier layers forming a finger portion. Moreover, the width and length of the barrier layer 3 are both smaller than the width and length of the channel layer 2.

[0070] S3: Plasma enhanced chemical vapor deposition technology is used to deposit a SiO2 layer on the device surface as an initial dielectric layer;

[0071] S4: etching the initial dielectric layer using a reactive ion etching process to obtain a dielectric layer 4 that is located on the channel layer 2 and forms a surrounding structure for the interdigitated portion of the barrier layer 3 .

[0072] S5: Use electron beam evaporation technology to evaporate metal on the barrier layer 3 and the epitaxial layer 1 to obtain a cathode electrode 5 and an anode electrode 6, wherein the cathode electrode 5 is located on the upper surface of the first barrier part of the barrier layer 3, and the anode electrode 6 and the transparent electrode are arranged on the epitaxial layer 1 in a cross-finger distribution manner.

[0073] For the specific contents of the preparation method of the ultraviolet photoelectric detector and the corresponding beneficial effects, please refer to the relevant contents of the ultraviolet photoelectric detector provided in the first aspect, which will not be repeated here.

[0074] 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.

[0075] 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. An ultraviolet photoelectric detector, characterized in that: include: epitaxial layer, channel layer, barrier layer, dielectric layer, cathode electrode and anode electrode; wherein, The epitaxial layer, the channel layer and the barrier layer are stacked from bottom to top; The channel layer and the barrier layer form a transparent electrode; The anode electrode is disposed on the epitaxial layer, and the anode electrode and the transparent electrode are arranged in a mutually interdigitated distribution manner; The cathode electrode is disposed on the barrier layer; The dielectric layer is located on the channel layer to form a surrounding structure for the interdigitated portion of the barrier layer, so as to isolate the anode electrode from the cathode electrode.

2. The ultraviolet photodetector according to claim 1, characterized in that: The material of the channel layer is unintentionally doped GaN or Al X Ga (1-X) N, where X is between 20% and 50%.

3. The ultraviolet photodetector according to claim 1, characterized in that: The channel layer includes a first channel portion and a second channel portion connected, the first channel portion is located on one side of the upper surface of the epitaxial layer, and the second channel portion includes a plurality of parallel strip channel layers to form an interdigitated portion, and one end of each strip channel layer is connected to the first channel portion.

4. The ultraviolet photodetector according to claim 3, characterized in that: The barrier layer includes a first barrier portion and a second barrier portion that are connected, the first barrier portion is located on the upper surface of the first channel portion, the second barrier portion includes a plurality of parallel strip barrier layers forming a finger portion, one end of each of the strip barrier layers is connected to the first barrier portion, and the strip barrier layers are located on the upper surface of the corresponding strip channel layer.

5. The ultraviolet photodetector according to claim 4, characterized in that: The cathode electrode is located on an upper surface of the first barrier portion.

6. The ultraviolet photodetector according to claim 1, characterized in that: The material of the dielectric layer is silicon nitride, silicon oxide, aluminum oxide, zirconium oxide or hafnium oxide.

7. The ultraviolet photodetector according to claim 1, characterized in that: The thickness of the dielectric layer is 10nm-200nm.

8. A method for preparing an ultraviolet photodetector, characterized in that: The ultraviolet photoelectric detector according to any one of claims 1 to 7, wherein the preparation method comprises: Step 1: preparing an epitaxial wafer, wherein the epitaxial wafer comprises an epitaxial layer, an initial channel layer and an initial barrier layer stacked in sequence from bottom to top; Step 2: etching the initial channel layer and the initial barrier layer to form a channel layer and a barrier layer, wherein the channel layer and the barrier layer form a transparent electrode, and the transparent electrode is distributed in an interdigitated shape; Step 3: preparing a dielectric layer on the channel layer, wherein the dielectric layer forms a surrounding structure for the interdigitated portion of the barrier layer; Step 4: preparing a cathode electrode on the barrier layer, and preparing an anode electrode on the epitaxial layer, wherein the anode electrode and the transparent electrode are arranged in a cross-finger distribution manner.

9. The method for preparing the ultraviolet photodetector according to claim 8, characterized in that: The step 3 comprises: Step 3.1: preparing an initial dielectric layer on the surface of the device on which the transparent electrode is formed; Step 3.2: Etching the initial dielectric layer to obtain a dielectric layer that is located on the channel layer and forms a surrounding structure for the interdigitated portion of the barrier layer.

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