An ultraviolet photodetector and its fabrication method

Abstract

This invention discloses an ultraviolet photodetector and its fabrication method, relating to the field of semiconductor optoelectronic devices. The ultraviolet photodetector includes an epitaxial layer, a channel layer, a barrier layer, a dielectric layer, a cathode electrode, and a cathode electrode. The epitaxial layer, channel layer, and barrier layer are stacked from bottom to top. The channel layer and barrier layer form transparent electrodes. The cathode electrode is disposed on the epitaxial layer, and the cathode electrode and transparent electrode are arranged in an interdigitated, cross-shaped distribution. The cathode electrode is disposed on the barrier layer. The dielectric layer is located on the channel layer, forming a surrounding structure around the interdigitated portion of the barrier layer to isolate the cathode electrode from the cathode electrode. In this invention, the alternating arrangement of metal and transparent interdigitated electrodes increases the electrode spacing in a single photolithography process, reduces the difficulty of metal stripping, and utilizes the dielectric layer to isolate the cathode and cathode electrodes, preventing short circuits and thus reducing the dark current of the ultraviolet photodetector.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic device technology, specifically relating to an ultraviolet photodetector and its preparation method. Background Technology

[0002] When light is incident, thin films coated with materials of different refractive indices produce specific optical properties. Specifically, each material exhibits unique optical characteristics for different wavelengths of light, and different material parameters result in different filtering effects. Therefore, by selecting a suitable dielectric thin film and adjusting its material parameters, the detector can selectively absorb incident light of a specific wavelength. Meanwhile, during detector fabrication, etching processes can block two-dimensional electron gas and reduce dark current, but they inevitably introduce defects and unstable surface states into the material surface. These surface states increase the recombination of photogenerated carriers.

[0003] GaN HEMT detectors possess unique advantages, enabling the fabrication of high-response ultraviolet detectors due to the presence of a two-dimensional electron gas. However, further improvements in the responsivity of such detectors largely depend on reducing the electrode spacing. Reducing the electrode spacing enhances the electric field strength and improves carrier collection efficiency, thereby increasing the detector's responsivity. However, due to current technological limitations, short circuits are highly likely to occur during the reduction of electrode spacing. This is because as the electrode spacing decreases, the precision requirements in the manufacturing process become extremely high; even minute process deviations can lead to electrodes becoming too close together, causing a short circuit. This technological challenge makes achieving higher responsivity while avoiding short circuits a pressing problem to be solved in actual production. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides an ultraviolet photodetector and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] This invention provides an ultraviolet photodetector, comprising: an epitaxial layer, a channel layer, a barrier layer, a dielectric layer, a cathode electrode, and a cathode 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 is disposed on the epitaxial layer, and the anode and the transparent electrode are arranged in an interdigitated pattern.

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

[0010] The dielectric layer is located on the channel layer and forms a surrounding structure around the interdigitated portion of the barrier layer to isolate the anode and the cathode.

[0011] In one embodiment of the present invention, the channel layer is made of 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 connected together. 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-shaped channel layers forming an interdigitated portion. One end of each strip-shaped channel layer 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 connected together. 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-shaped barrier layers forming an interdigitated portion. One end of each strip-shaped barrier layer is connected to the first barrier portion. The strip-shaped barrier layer is located on the upper surface of the corresponding strip-shaped channel layer.

[0014] In one embodiment of the present invention, the cathode is located on the upper surface of the first 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] This invention provides a method for fabricating an ultraviolet photodetector, applicable to the ultraviolet photodetector described in any of the above embodiments, the fabrication method comprising:

[0018] Step 1: Prepare an epitaxial wafer, which includes an epitaxial layer, an initial channel layer and an initial barrier layer stacked sequentially from bottom to top;

[0019] Step 2: Etch the initial channel layer and the initial barrier layer to form the channel layer and the barrier layer. The channel layer and the barrier layer form transparent electrodes, which are distributed in an interdigitated pattern.

[0020] Step 3: Fabricate a dielectric layer on the channel layer, wherein the dielectric layer forms an enclosing structure around the interdigitated portion of the barrier layer;

[0021] Step 4: Fabricate a cathode on the barrier layer and a anode on the epitaxial layer. The anode and the transparent electrode are arranged in an interdigitated pattern.

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

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

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

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The ultraviolet photodetector of the present invention includes an epitaxial layer, a channel layer, a barrier layer, a dielectric layer, a cathode electrode, and a cathode 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 transparent electrodes; the cathode electrode is disposed on the epitaxial layer, and the cathode electrode and the transparent electrode are arranged in an interdigitated, cross-shaped distribution; the cathode electrode is disposed on the barrier layer; the dielectric layer is located on the channel layer and forms a surrounding structure around the interdigitated portion of the barrier layer to isolate the cathode electrode from the cathode electrode. In the present invention, the alternating arrangement of metal interdigitated and transparent interdigitated electrodes can increase the electrode spacing in a single photolithography, reduce the difficulty of metal stripping, and utilize the dielectric layer to isolate the cathode and cathode electrodes, preventing short circuits between the cathode and cathode electrodes, thereby reducing the dark current of the ultraviolet photodetector.

[0027] 2. The ultraviolet photodetector of the present invention can achieve selective light detection by changing 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 also acts as a passivation material to reduce the surface states introduced by etching, repair etching damage, thereby reducing the recombination of photogenerated carriers and improving quantum efficiency.

[0028] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a side view of an ultraviolet photodetector provided in an embodiment of the present invention;

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

[0031] Figure 3This is a flowchart of a method for fabricating an ultraviolet photodetector provided in an embodiment of the present invention;

[0032] Figure 4 This is a process flow diagram of the fabrication of an ultraviolet photodetector provided in an embodiment of the present invention.

[0033] Icons: 1-Epipolar layer; 2-Channel layer; 3-Barrier layer; 4-Dielectric layer; 5-Cathode; 6-Anode. Detailed Implementation

[0034] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a detailed explanation of an ultraviolet photodetector and its preparation method based on the present invention.

[0035] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0036] Firstly, embodiments of the present invention provide an ultraviolet photodetector, please refer to [reference needed]. Figure 1 and Figure 2 , Figure 1 This is a side view of an ultraviolet photodetector provided in an embodiment of the present invention; Figure 2 This is a top view of an ultraviolet photodetector provided in 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 5, and a cathode 6. The epitaxial layer 1, channel layer 2, and barrier layer 3 are stacked from bottom to top; the channel layer 2 and barrier layer 3 form transparent electrodes; the cathode 6 is disposed on the epitaxial layer 1, and the cathode 6 and transparent electrodes are arranged in an interdigitated, cross-shaped distribution; the cathode 5 is disposed on the barrier layer 3; the dielectric layer 4, located on the channel layer 2, forms a surrounding structure around the interdigitated portion of the barrier layer 3 to isolate the cathode 6 from the cathode 5.

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

[0039] In an optional embodiment, the channel layer 2 is made of 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 connected together. 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-shaped channel layers forming an interdigitated portion. One end of each strip-shaped channel layer 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 together. 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-shaped barrier layers forming an interdigitated portion. One end of each strip-shaped barrier layer is connected to the first barrier portion, and the strip-shaped barrier layer is located on the upper surface of the corresponding strip-shaped channel layer.

[0043] In this embodiment, the cathode 5 is located on the upper surface of the first barrier layer. 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 dielectric layer 4 is made of silicon nitride (SiN). X (e.g., silicon dioxide (SiO2), aluminum oxide (Al2O3), zirconium oxide (Tm2O3)) or hafnium oxide (HfO2).

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

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

[0047] For photodetectors with bimetallic interdigitated electrodes, reducing the electrode spacing brings the non-equilibrium carriers generated by light injection closer to the electrodes, effectively reducing recombination of photogenerated carriers during diffusion and increasing external quantum efficiency. However, when the electrode spacing is reduced to the nanometer level, metal easily remains in the interdigital gaps, making it difficult to peel off. In the ultraviolet photodetector of this invention, metal interdigitates and transparent interdigitates are arranged alternately. Due to the asymmetric electrode structure—that is, a transparent electrode in the middle of a metal electrode on one side—the electrode spacing in a single photolithography step can be increased. Therefore, while reducing the electrode spacing, the difficulty of metal peeling is also reduced.

[0048] Since metal residues easily remain in the interdigitated gaps, these residues can short-circuit the anode and cathode, increasing the dark current of the device. In the ultraviolet photodetector of this invention, a dielectric layer is introduced to fill the interdigitated gaps, providing isolation between the anode and cathode and preventing short circuits, thereby reducing the dark current of the ultraviolet photodetector. Furthermore, the dielectric layer of this invention also serves as a passivation material, reducing surface states introduced by etching, repairing etching damage, thereby reducing recombination of photogenerated carriers and improving quantum efficiency.

[0049] Secondly, embodiments of the present invention provide a method for fabricating an ultraviolet photodetector, applicable to the ultraviolet photodetector provided in the first aspect. Please refer to... Figure 3 , Figure 3 This is a flowchart illustrating a method for fabricating an ultraviolet photodetector according to an embodiment of the present invention. Figure 3 As shown, the fabrication method of the ultraviolet photodetector in 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 sequentially from bottom to top.

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

[0052] Alternatively, the epitaxial layer, initial channel layer, and initial barrier layer can be prepared using metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or hydride vapor phase epitaxy (HVPE).

[0053] Step 2: Etch the initial channel layer and the initial barrier layer to form the channel layer and the barrier layer. The channel layer and the barrier layer form transparent electrodes, which are distributed in an interdigitated pattern.

[0054] In this embodiment, the channel layer includes a first channel portion and a second channel portion connected together. 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-shaped channel layers forming interdigitated portions. One end of each strip-shaped channel layer is connected to the first channel portion. The barrier layer includes a first barrier portion and a second barrier portion connected together. 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-shaped barrier layers forming interdigitated portions. One end of each strip-shaped barrier layer is connected to the first barrier portion, and the strip-shaped barrier layers are located on the upper surface of the corresponding strip-shaped channel layers.

[0055] Optionally, inductively coupled plasma etching, wet etching, or dry etching processes can be used to etch the initial channel layer and the initial barrier layer 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 an enclosing structure around the interdigitated portion of the barrier layer.

[0057] Optionally, step 3 includes:

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

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

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

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

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

[0063] Step 4: Fabricate a cathode on the barrier layer and a cathode on the epitaxial layer. The cathode and transparent electrode are arranged in an interdigitated pattern.

[0064] Alternatively, metal can be deposited on the barrier layer and the epitaxial layer using electron beam evaporation deposition technology to form the cathode and anode.

[0065] The method for fabricating the ultraviolet photodetector in this invention is simple, low-cost, and suitable for large-scale production.

[0066] Furthermore, the specific process of fabricating the ultraviolet photodetector of the present invention will be described with reference to specific embodiments. Please refer to [link to documentation]. Figure 4 , Figure 4 This is a process flow diagram of the fabrication of an ultraviolet photodetector provided in an embodiment of the present invention. For example... Figure 4 As shown, the fabrication method of the ultraviolet photodetector in this embodiment includes:

[0067] S1: Sapphire substrate is selected as wafer substrate, and AlGaN layer, unintentionally doped GaN layer and AlGaN layer are epitaxially grown sequentially on the wafer substrate using hydride vapor phase epitaxy technology as epitaxial layer 1, initial channel layer and initial barrier layer.

[0068] S2: The initial channel layer and the initial barrier layer are etched using an inductively coupled plasma etching process to form the channel layer 2 and the barrier layer 3.

[0069] The channel layer 2 includes a first channel portion and a second channel portion connected together. The second channel portion is perpendicular to the first channel portion and includes multiple parallel strip-shaped channel layers forming an interdigitated portion. The barrier layer 3 includes a first barrier portion and a second barrier portion connected together. The second barrier portion is perpendicular to the first barrier portion and includes multiple parallel strip-shaped barrier layers forming an interdigitated portion. Furthermore, the width and length of the barrier layer 3 are both smaller than those of the channel layer 2.

[0070] S3: A SiO2 layer is deposited on the device surface as the initial dielectric layer using plasma-enhanced chemical vapor deposition (PECVD).

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

[0072] S5: Electron beam evaporation deposition technology is used to deposit metal on barrier layer 3 and epitaxial layer 1 to obtain cathode electrode 5 and anode electrode 6. Cathode electrode 5 is located on the upper surface of the first barrier part of barrier layer 3, and anode electrode 6 and transparent electrode are arranged on epitaxial layer 1 in an interdigitated distribution.

[0073] For details regarding the fabrication method of the ultraviolet photodetector and its corresponding beneficial effects, please refer to the relevant content on the ultraviolet photodetector provided in the first aspect; it will not be repeated here.

[0074] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0075] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An ultraviolet photodetector, characterized in that, include: Epitaxial layer, channel layer, barrier layer, dielectric layer, cathode electrode, and anode electrode; among which, 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; wherein, the channel layer includes a first channel portion and a second channel portion connected together, the first channel portion being located on one side of the upper surface of the epitaxial layer, and the second channel portion including a plurality of parallel strip-shaped channel layers forming interdigitated portions, one end of each strip-shaped channel layer being connected to the first channel portion; the barrier layer includes a first barrier portion and a second barrier portion connected together, the first barrier portion being located on the upper surface of the first channel portion, and the second barrier portion including a plurality of parallel strip-shaped barrier layers forming interdigitated portions, one end of each strip-shaped barrier layer being connected to the first barrier portion, and the strip-shaped barrier layer being located on the upper surface of the corresponding strip-shaped channel layer; The anode is disposed on the epitaxial layer, and the anode and the transparent electrode are arranged in an interdigitated pattern. The cathode is disposed on the barrier layer; The dielectric layer is located on the channel layer and forms a surrounding structure around the interdigitated portion of the barrier layer to isolate the anode and the cathode.

2. The ultraviolet photodetector according to claim 1, characterized in that, The channel layer is made of 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 cathode is located on the upper surface of the first barrier portion.

4. 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.

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

6. A method for fabricating an ultraviolet photodetector, characterized in that, The method for preparing the ultraviolet photodetector according to any one of claims 1-5 includes: Step 1: Prepare an epitaxial wafer, which includes an epitaxial layer, an initial channel layer and an initial barrier layer stacked sequentially from bottom to top; Step 2: Etch the initial channel layer and the initial barrier layer to form the channel layer and the barrier layer. The channel layer and the barrier layer form transparent electrodes, which are distributed in an interdigitated pattern. Step 3: Fabricate a dielectric layer on the channel layer, wherein the dielectric layer forms an enclosing structure around the interdigitated portion of the barrier layer; Step 4: Fabricate a cathode on the barrier layer and a anode on the epitaxial layer. The anode and the transparent electrode are arranged in an interdigitated pattern.

7. The method for fabricating an ultraviolet photodetector according to claim 6, characterized in that, Step 3 includes: Step 3.1: Prepare an initial dielectric layer on the surface of the device where the transparent electrode is formed; Step 3.2: Etch the initial dielectric layer to obtain a dielectric layer located on the channel layer that forms a surrounding structure on the interdigitated portion of the barrier layer.

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