GaN-based gradient doped extreme ultraviolet detector and preparation method thereof

Abstract

The invention relates to the technical field of semiconductors, and provides a GaN-based gradient doped extreme ultraviolet detector and a preparation method thereof. The GaN-based gradient doping extreme ultraviolet detector comprises a substrate, a GaN buffer layer, an n-GaN layer, an i-GaN layer, an n-type electrode, a gradient doping p-GaN layer and a p-type electrode, and the doping concentration of the gradient doping p-GaN layer is gradually reduced in the direction from the surface, close to the p-type electrode, of the gradient doping p-GaN layer to the surface, away from the p-type electrode, of the gradient doping p-GaN layer; according to the GaN-based gradient doping extreme ultraviolet detector, a surface electric field can be induced by utilizing the gradient doping p-GaN layer, and the electric field can drive photon-excited electron-hole pair separation, so that the surface carrier collection capability of an EUV wave band is remarkably improved; the surface electric field formed by the gradient doping p-GaN layer is utilized, the light current and the responsivity of the detector are improved, and the structure has a wide application prospect in the extreme ultraviolet GaN-based detector.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a GaN-based gradient-doped extreme ultraviolet detector and its fabrication method. Background Technology

[0002] EUV (Extreme Ultraviolet) lithography, based on a 13.5 nm light source, has enabled the successful implementation of 7 nm node integrated circuit manufacturing processes. EUV detectors are key components used to monitor and calibrate photon beam intensity. Currently, mainstream silicon-based EUV detectors possess good quantum efficiency and relatively mature fabrication techniques, but they are susceptible to damage under harsh environments or high-dose ultraviolet radiation, thus affecting their reliability. Therefore, researching and developing semiconductor materials with high resistance to extreme ultraviolet radiation is crucial to solving radiation damage issues in devices. GaN-based materials are direct wide-bandgap semiconductors with continuously tunable bandgap widths between 0.9 eV and 6.2 eV, and exhibit excellent thermal and chemical stability, making them ideal materials for fabricating extreme ultraviolet detectors.

[0003] Because extreme ultraviolet (EUV) light has a very shallow penetration depth, pin-type photodiodes exhibit very low quantum efficiency in the EUV region. A significant proportion of incident photons are absorbed by the ohmic contact layer at the top of the pn junction, contributing nothing to the photocurrent and resulting in extremely low quantum efficiency (QE) in the EUV band. Currently, GaN-based pin detectors typically use i-GaN as the light-absorbing layer and achieve the separation and collection of photogenerated carriers under an applied electric field. Furthermore, GaN-based materials inherently contain numerous dislocations; these defects and damage can lead to device failure and increased dark current, impairing device performance and stability.

[0004] Given the shortcomings of current GaN-based pin detectors, it is necessary to improve them. Summary of the Invention

[0005] In view of this, in order to reduce the strong surface absorption loss of extreme ultraviolet detectors and improve their photocurrent and responsivity, this invention proposes a GaN-based gradient-doped extreme ultraviolet detector and its fabrication method.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a GaN-based gradient-doped extreme ultraviolet detector, comprising: Substrate; A GaN buffer layer is located on the surface of the substrate; An n-GaN layer is located on the surface of the GaN buffer layer away from the substrate; The i-GaN layer is located on the surface of the n-GaN layer away from the substrate; The n-type electrode is located on the surface of the n-GaN layer away from the substrate, and the i-GaN layer and the n-type electrode are located on opposite sides of the surface of the n-GaN layer, respectively. A gradient-doped p-GaN layer is located on the surface of the i-GaN layer away from the substrate; The p-type electrode is located on the surface of the gradient-doped p-GaN layer away from the substrate; The doping concentration of the gradient-doped p-GaN layer gradually decreases from the surface of the gradient-doped p-GaN layer near the p-type electrode to the surface away from the p-type electrode.

[0007] Preferably, the doping concentration of the gradient-doped p-GaN layer varies from (2~3)×10⁻⁶ in the direction from the surface of the gradient-doped p-GaN layer near the p-type electrode to the surface away from the p-type electrode. 19 cm -3 Reduced to (1~2)×10 16 cm -3 .

[0008] Preferably, the thickness of the gradient-doped p-GaN layer is 50~150 nm.

[0009] Preferably, the thickness of the n-GaN layer is ≥400 nm, and the doping concentration is ≥5 × 10⁻⁶. 18 cm -3 .

[0010] Preferably, the i-GaN layer is an unintentionally doped GaN layer, and the thickness of the i-GaN layer is 400~500nm.

[0011] Preferably, the substrate is a heterogeneous substrate or a homogeneous substrate; The heterogeneous substrate includes any one of sapphire substrate, silicon carbide substrate, and silicon substrate; The homogeneous substrate includes a GaN substrate or an AlN substrate.

[0012] Preferably, the material of the n-type electrode includes at least one of Pt, Ti, Ni, and Au; The material of the p-type electrode includes at least one of Ni, Pt, and Au.

[0013] Preferably, the thickness of the n-type electrode is 50~300 nm; The thickness of the p-type electrode is 3~5 nm; The thickness of the GaN buffer layer is 50~200 nm.

[0014] Secondly, the present invention also provides a method for fabricating the GaN-based gradient-doped extreme ultraviolet detector, comprising the following steps: A GaN buffer layer is epitaxially grown on the substrate surface; An n-GaN layer is deposited on the surface of the GaN buffer layer; An i-GaN layer is deposited on one side of the surface of the n-GaN layer; A gradient-doped p-GaN layer is deposited on the surface of the i-GaN layer; Etch the device mesa until the n-GaN layer is exposed; An n-type electrode is deposited on the surface of the n-GaN layer in the etched region below the mesa; A p-type electrode is deposited on the surface of the gradient-doped p-GaN layer.

[0015] Preferably, it includes the following steps: A GaN buffer layer and an n-GaN layer are epitaxially grown sequentially on the substrate surface; i-GaN material and gradient-doped p-GaN material are grown on the surface of the n-GaN layer, and a SiO2 mask layer is grown on the outside of the gradient-doped p-GaN material. A mesa pattern is photolithographically etched on the SiO2 mask layer. The SiO2 mask layer that is not covered by photoresist in the non-mesa pattern area is etched away. The area not covered by the SiO2 mask layer is etched to the n-GaN layer. The SiO2 mask layer in the mesa area is removed to obtain the gradient-doped p-GaN layer and i-GaN layer. A photoresist mask pattern for an n-type electrode is prepared on top of an n-GaN layer using photolithography. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, n-type electrode material is deposited on the photoresist mask pattern. The photoresist and the electrode material covering it are then removed. Finally, annealing is performed to obtain the n-type electrode. A photoresist mask pattern for a p-type electrode is prepared on top of a gradient-doped p-GaN layer using photolithography. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, p-type electrode material is deposited on the photoresist mask pattern, and the photoresist and the electrode material covering it are removed. Finally, annealing is performed to obtain the p-type electrode.

[0016] The GaN-based gradient-doped extreme ultraviolet detector of the present invention has the following advantages over the prior art: The GaN-based gradient-doped extreme ultraviolet (EUV) detector of the present invention includes a substrate, a GaN buffer layer, an n-GaN layer, an i-GaN layer, an n-type electrode, a gradient-doped p-GaN layer, and a p-type electrode. The doping concentration of the gradient-doped p-GaN layer gradually decreases from the surface of the p-type electrode towards the surface away from the p-type electrode. The gradient-doped p-GaN layer induces a surface electric field that drives the separation of photon-excited electron-hole pairs, thereby significantly improving the surface carrier collection capability in the EUV band. The gradient-doped p-type GaN layer serves as the absorption layer of the detector, absorbing ultraviolet signals. The GaN-based gradient-doped EUV detector of the present invention utilizes the surface electric field induced by the gradient-doped p-GaN layer, which drives the separation of photon-excited electron-hole pairs, thereby significantly improving the surface carrier collection capability in the EUV band. The detector of the present invention utilizes the surface electric field formed by the gradient-doped p-GaN layer to improve the photocurrent and responsivity of the detector. This structure has broad application prospects in EUV GaN-based detectors. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the GaN-based gradient-doped extreme ultraviolet detector of the present invention; Figure 2 This is a flowchart of the fabrication method of the GaN-based gradient-doped extreme ultraviolet detector of the present invention; Figure 3 The electric field strength at the underside of the stage at different thicknesses of the detector in Example 1 and Comparative Example 1; Figure 4 The graphs show the changes in photocurrent of the detectors as a function of voltage in Example 1 and Comparative Example 1. Figure 5 The graph shows the change in the responsivity of the detectors in Example 1 and Comparative Example 1 as a function of voltage. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0021] In the description of this invention, it should be understood that the orientation or positional relationship indicated by terms such as "above" is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, or the orientation or positional relationship in which those skilled in the art are usually understood. It is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] The following provides a detailed description of each example. It should be noted that the order of description of the embodiments below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0023] This invention provides a GaN-based gradient-doped extreme ultraviolet detector, such as... Figure 1 Shown, including: Substrate 1; GaN buffer layer 2 is located on the surface of substrate 1; n-GaN layer 3 is located on the surface of GaN buffer layer 2 away from substrate 1; i-GaN layer 4 is located on the surface of n-GaN layer 3 away from substrate 1; The n-type electrode 5 is located on the surface of the n-GaN layer 3 away from the substrate 1, and the i-GaN layer 4 and the n-type electrode 5 are located on both sides of the surface of the n-GaN layer 3, respectively. Gradient-doped p-GaN layer 6 is located on the surface of i-GaN layer 4 away from substrate 1; p-type electrode 7 is located on the surface of gradient-doped p-GaN layer 6 away from substrate 1; In particular, the doping concentration of the gradient-doped p-GaN layer 6 gradually decreases from the surface of the gradient-doped p-GaN layer near the p-type electrode to the surface away from the p-type electrode.

[0024] The GaN-based gradient-doped extreme ultraviolet detector of the present invention includes a substrate 1, a GaN buffer layer 2, an n-GaN layer 3, an i-GaN layer 4, an n-type electrode 5, a gradient-doped p-GaN layer 6, and a p-type electrode 7; wherein the substrate 1, GaN buffer layer 2, and n-GaN layer 3 are stacked sequentially, and the i-GaN layer 4 and n-type electrode 5 are located on opposite sides of the surface of the n-GaN layer 3; the gradient-doped p-GaN layer 6 is located on the surface of the i-GaN layer 4; and the p-type electrode 7 is located on the surface of the gradient-doped p-GaN layer 6; wherein, the doping concentration of the gradient-doped p-GaN layer 6 gradually decreases from the surface of the gradient-doped p-GaN layer 6 near the p-type electrode 7 to the surface away from the p-type electrode 7, that is, in the thickness direction of the gradient-doped p-GaN layer 6 and... Figure 1 From top to bottom, the doping concentration gradually decreases; the n-GaN layer serves as the n-type region of the detector and simultaneously forms an ohmic contact with the n-type electrode; the gradient-doped p-GaN layer induces a surface electric field, which can drive the separation of photon-excited electron-hole pairs, thereby significantly improving the surface carrier collection capability in the EUV band; the gradient-doped p-type GaN layer serves as the absorption layer of the detector, absorbing ultraviolet signals; the gradient-doped p-GaN layer forms a low-barrier Schottky contact with the p-type electrode; the GaN-based gradient-doped extreme ultraviolet detector of this invention utilizes the surface electric field induced by the gradient-doped p-GaN layer (e.g., ... Figure 3 As shown), this electric field can drive the separation of photon-excited electron-hole pairs, thereby significantly improving the surface carrier collection capability in the EUV band; the detector of this invention utilizes the surface electric field formed by the gradient-doped p-GaN layer to improve the photocurrent of the detector (e.g. Figure 4 (as shown) and responsiveness (as shown) Figure 5 As shown in the figure, this structure has broad application prospects in extreme ultraviolet GaN-based detectors.

[0025] Specifically, the n-GaN layer, or n-type gallium nitride layer, is a conductive layer that primarily uses electrons as charge carriers by doping gallium nitride with specific impurity atoms; these impurity atoms are usually donor impurities such as silicon (Si); the i-GaN layer, or intrinsic gallium nitride layer, is a gallium nitride layer that basically does not contain intentionally doped impurities; and the p-GaN layer, or p-type gallium nitride layer, is a conductive layer that primarily uses holes as charge carriers by doping gallium nitride with acceptor impurities such as magnesium (Mg).

[0026] In some embodiments, the direction from the surface of the gradient-doped p-GaN layer near the p-type electrode to the surface away from the p-type electrode, i.e. Figure 1In the gradient-doped p-GaN layer, along the thickness direction from top to bottom, the doping concentration of the gradient-doped p-GaN layer increases from (2~3)×10⁶. 19 cm -3 Reduced to (1~2)×10 16 cm -3 For example, the doping concentration is 2 × 10 19 cm -3 Reduced to 1×10 16 cm -3 For example, the doping concentration is 2×10 19 cm -3 Reduced to 1.5×10 19 cm -3 1×10 19 cm -3 5×10 18 cm -3 1×10 18 cm -3 5×10 17 cm -3 1×10 17 cm -3 5×10 16 cm -3 4×10 16 cm -3 3×10 16 cm -3 2×10 16 cm -3 1×10 16 cm -3 .

[0027] In some embodiments, the gradient-doped p-GaN layer 6 comprises multiple doped p-GaN layers from top to bottom, and the doping concentration of the multiple doped p-GaN layers from top to bottom increases from 2 × 10⁻⁶. 19 cm -3 Reduced to 1×10 16 cm -3 That is, the doping concentration of the topmost doped p-GaN layer is 2×10⁻⁶. 19 cm -3 The doping concentration of the bottom p-GaN layer is 1×10⁻⁶. 16 cm -3 .

[0028] In some embodiments, the thickness of the gradient-doped p-GaN layer is 50~150 nm.

[0029] In some embodiments, the thickness of the n-GaN layer 3 is ≥400 nm, and the doping concentration is ≥5 × 10⁻⁶. 18 cm -3 .

[0030] In some embodiments, the i-GaN layer 4 is an unintentionally doped GaN layer with a thickness of 400~500nm.

[0031] In some embodiments, substrate 1 is a heterogeneous substrate or a homogeneous substrate; Heterogeneous substrates include any one of sapphire substrates, silicon carbide substrates, and silicon substrates; Homogeneous substrates include GaN substrates or AlN substrates.

[0032] In some embodiments, the n-type electrode 5 is an ohmic contact electrode, and the material of the n-type electrode 5 includes at least one of Pt, Ti, Ni, and Au. Specifically, the material of the n-type electrode 5 is any one of Pt, Ti, Ni, and Au, or an alloy of two or more of Pt, Ti, Ni, and Au.

[0033] In some embodiments, the p-type electrode 7 is an ultrathin semi-transparent electrode or a grid electrode, and the material of the p-type electrode 7 includes at least one of Ni, Pt, and Au.

[0034] In some embodiments, the thickness of the n-type electrode 5 is 50~300 nm.

[0035] In some embodiments, the thickness of the p-type electrode 7 is 3~5 nm.

[0036] In some embodiments, the thickness of the GaN buffer layer 2 is 50~200 nm.

[0037] Based on the same inventive concept, this invention also provides a method for fabricating the above-mentioned GaN-based gradient-doped extreme ultraviolet detector, such as... Figure 2 As shown, it includes the following steps: S1. Epitaxially grow a GaN buffer layer on the substrate surface; S2. An n-GaN layer is deposited on the surface of the GaN buffer layer; S3. An i-GaN layer is deposited on one side of the surface of the n-GaN layer; S4. A gradient-doped p-GaN layer is deposited on the surface of the i-GaN layer; S5. Etch the device mesa until the n-GaN layer is exposed; S6. An n-type electrode is deposited on the surface of the n-GaN layer in the etched region below the mesa; S7. A p-type electrode is deposited on the surface of the gradient-doped p-GaN layer.

[0038] In some embodiments, the fabrication method of a GaN-based gradient-doped extreme ultraviolet detector includes the following steps: S1. Growth of device epitaxial materials: GaN buffer layer, n-GaN layer, i-GaN material, and gradient-doped p-GaN material are sequentially epitaxially grown on the substrate surface; S2. Fabrication of mesa structure: A SiO2 mask layer is grown on the outside of the gradient-doped p-GaN material. A mesa pattern is etched on the SiO2 mask layer using photolithography. The SiO2 mask layer in the non-mesa pattern area is etched away using RIE technology. The area without SiO2 mask layer coverage is etched to the n-GaN layer using ICP technology. The SiO2 mask layer in the mesa area is removed using HF to obtain the gradient-doped p-GaN layer and i-GaN layer. S3. Fabrication of n-type electrodes: Photolithography is used to fabricate a photoresist mask pattern for n-type electrodes above the n-GaN layer. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, n-type electrode material is deposited on the photoresist mask pattern. The Lift Off technique is then used to remove the photoresist and the electrode material covering it. Finally, annealing is performed to obtain the n-type electrodes. S4. Fabrication of p-type electrode: A photoresist mask pattern for a p-type electrode is fabricated on top of a gradient-doped p-GaN layer using photolithography. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, p-type electrode material is deposited on the photoresist mask pattern. The photoresist and the electrode material covering it are then removed using lift-off technology. Finally, annealing is performed to obtain the p-type electrode.

[0039] In some embodiments, the method for growing epitaxial materials for the device in step S1 is MOCVD or MBE.

[0040] In some embodiments, in step S2, photolithography is used, and the selection of positive and negative photoresists is determined according to the design of the photomask pattern window, so that the photoresist in the surface area is retained after development, and the photoresist in the non-surface area is removed.

[0041] In some embodiments, in steps S3 and S4, photolithography is used, and the selection of positive and negative photoresists is determined according to the design of the photomask pattern window, so that the photoresist in the electrode pattern area is removed after development, while the photoresist in the non-electrode area is retained.

[0042] In some embodiments, in steps S3 and S4, the method used for vapor deposition of n-type electrode material and p-type electrode material is electron beam evaporation or thermal evaporation technology.

[0043] In some embodiments, the annealing process is as follows: annealing the n-type electrode and the p-type electrode in a nitrogen atmosphere using an annealing furnace, wherein the annealing temperature and time are determined by the electrode material; for example, when the n-type electrode and the p-type electrode material is Pt, the annealing temperature is 400~600℃ and the annealing time is 5~10min; when the n-type electrode material is Ti, the annealing temperature is 300~500℃ and the annealing time is 5~15min; when the n-type electrode and the p-type electrode material is Ni, the annealing temperature is 300~500℃ and the annealing time is 10~15min; when the n-type electrode and the p-type electrode material is Au, the annealing temperature is 200~400℃ and the annealing time is 10~20min.

[0044] In some embodiments, the GaN buffer layer is deposited using ammonia and gallium source (commonly trimethylgallium (TMGa)) as raw materials. The carrier gas is usually hydrogen (H2) or nitrogen (N2) with a flow rate of 5 to 20 slm, the growth temperature is 500 to 600°C, the TMGa flow rate is 50 to 150 sccm, and the NH3 flow rate is 3000 to 5000 sccm.

[0045] In some embodiments, the i-GaN layer is deposited using ammonia and gallium source (commonly trimethylgallium (TMGa)) as raw materials, with a growth temperature of 1000~1100℃, a reaction chamber pressure controlled at 100~300 Torr, and gas flow rates of TMGa: 50~150 sccm, NH3: 3000~5000 sccm, and carrier gas: H2: 10~15 slm.

[0046] In some embodiments, an n-GaN layer is prepared using an n-type doping source: silane (SiH4). The process parameters are as follows: growth temperature is 1000~1100℃, reaction chamber pressure is 100~300 Torr; gas flow rate: TMGa flow rate is 50~150 sccm, NH3 flow rate is 3000~5000 sccm, SiH4 flow rate is 0.1~10 sccm, and carrier gas flow rate: H2 flow rate is 10~15 slm.

[0047] In some embodiments, a p-GaN layer is prepared using a p-type doping source: dicyclopentadienyl magnesium (Cp2Mg). The process parameters are as follows: growth temperature is 800~900℃, reaction chamber pressure is 100~300 Torr; gas flow rate: TMGa flow rate is 50~150 sccm, NH3 flow rate is 3000~5000 sccm, Cp2Mg flow rate is adjusted according to the required doping concentration, generally 1~10 sccm, and carrier gas flow rate: H2 flow rate is 10~15 slm.

[0048] The following detailed embodiments further illustrate the GaN-based gradient-doped extreme ultraviolet detector and its fabrication method. This section further explains the invention in conjunction with specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in the art.

[0049] Example 1 This application provides a GaN-based gradient-doped extreme ultraviolet detector, comprising: Substrate; A GaN buffer layer is located on the substrate surface; The n-GaN layer is located on the surface of the GaN buffer layer away from the substrate; The i-GaN layer is located on the surface of the n-GaN layer away from the substrate; The n-type electrode is located on the surface of the n-GaN layer away from the substrate 1, and the i-GaN layer and the n-type electrode are located on both sides of the surface of the n-GaN layer, respectively. A gradient-doped p-GaN layer is located on the surface of the i-GaN layer away from the substrate. The p-type electrode is located on the surface of the gradient-doped p-GaN layer away from the substrate. The gradient-doped p-GaN layer consists of 10 doped p-GaN layers from top to bottom, with the doping concentration of the 10 doped p-GaN layers increasing from 2 × 10⁻⁶ to 10⁻⁶. 19 cm -3 Reduced to 1×10 16 cm -3 Furthermore, the doping concentrations of the 10 doped p-GaN layers from top to bottom are 2×10⁻⁶. 19 cm -3 1.5×10 19 cm -3 1×10 19 cm -3 5×10 18 cm -3 1×10 18 cm -3 5×10 17 cm -3 1×10 17 cm -3 5×10 16 cm -3 3×10 16 cm -3 1×10 16 cm -3 The total thickness of the gradient-doped p-GaN layers is 150 nm, and the thickness of each doped p-GaN layer is 15 nm. The n-GaN layer has a thickness of 500 nm and a doping concentration of 8 × 10⁻⁶. 18 cm -3 ; The i-GaN layer is an unintentionally doped GaN layer with a thickness of 400 nm. The substrate is a sapphire substrate with a thickness of [missing information]. The n-type electrode consists of a Pt layer (50 nm thick), a Ti layer (50 nm thick), a Ni layer (50 nm thick), and an Au layer (50 nm thick) stacked sequentially, with the Pt layer in contact with the n-GaN layer; The p-type electrode is made of Ni and has a thickness of 5 nm. The thickness of the GaN buffer layer is 100 nm.

[0050] The above-mentioned method for fabricating a GaN-based gradient-doped extreme ultraviolet detector includes the following steps: S1. Epitaxial materials for growing devices: GaN buffer layer, n-GaN layer, i-GaN material and gradient-doped p-GaN material are epitaxially grown sequentially on the substrate surface using the MOVCD method; S2. Fabrication of mesa structure: A SiO2 mask layer is grown on the outside of the gradient-doped p-GaN material. A mesa pattern is etched on the SiO2 mask layer using photolithography. The SiO2 mask layer in the non-mesa pattern area is etched away using RIE technology. The area without SiO2 mask layer coverage is etched to the n-GaN layer using ICP technology. The SiO2 mask layer in the mesa area is removed using HF to obtain the gradient-doped p-GaN layer and i-GaN layer. S3. Fabrication of n-type electrodes: Photolithography is used to fabricate a photoresist mask pattern for n-type electrodes above the n-GaN layer. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, n-type electrode material is deposited on the photoresist mask pattern. The Lift Off technique is then used to remove the photoresist and the electrode material covering it. Finally, annealing is performed to obtain the n-type electrodes. S4. Fabrication of p-type electrode: A photoresist mask pattern for a p-type electrode is fabricated on top of a gradient-doped p-GaN layer using photolithography. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, p-type electrode material is deposited on the photoresist mask pattern. The photoresist and the electrode material covering it are then removed using lift-off technology. Finally, annealing is performed to obtain the p-type electrode. In the preparation of the n-type electrode, the annealing temperature is 450℃ and the annealing time is 5min; When preparing the p-type electrode, the annealing temperature is 400℃ and the annealing time is 10min; The GaN buffer layer preparation process parameters are as follows: nitrogen flow rate is 15 slm, growth temperature is 550℃, TMGa flow rate is 100 sccm, and NH3 flow rate is 4000 sccm. The i-GaN layer preparation process parameters are as follows: growth temperature is 1100℃, reaction chamber pressure is 150 Torr, gas flow rate: TMGa flow rate: 120 sccm, NH3 flow rate: 4500 sccm, carrier gas flow rate: H2 flow rate is 12 slm; The n-GaN layer preparation process parameters are as follows: growth temperature is 1050℃, reaction chamber pressure is 200 Torr; gas flow rate: TMGa flow rate is 80 sccm, NH3 flow rate is 4200 sccm, SiH4 flow rate is determined according to doping concentration, and carrier gas flow rate: H2 flow rate is 12 slm. The process parameters for preparing the doped p-GaN layer are as follows: growth temperature is 850℃, reaction chamber pressure is 150 Torr; gas flow rate: TMGa flow rate is 120 sccm, NH3 flow rate is 4000 sccm, Cp2Mg flow rate is adjusted according to the required doping concentration, and carrier gas flow rate: H2 flow rate is 10 slm.

[0051] Comparative Example 1 This comparative example provides a GaN-based extreme ultraviolet detector, including: Substrate; A GaN buffer layer is located on the substrate surface; The n-GaN layer is located on the surface of the GaN buffer layer away from the substrate; The i-GaN layer is located on the surface of the n-GaN layer away from the substrate; The n-type electrode is located on the surface of the n-GaN layer away from the substrate 1, and the i-GaN layer and the n-type electrode are located on both sides of the surface of the n-GaN layer, respectively. The p-GaN layer is located on the surface of the i-GaN layer away from the substrate; The p-type electrode is located on the surface of the gradient-doped p-GaN layer away from the substrate. Performance testing Figures 3-5 The detector with a gradient doping layer represents the detector in Example 1, and the detector without a gradient doping layer represents the detector in Comparative Example 1.

[0052] from Figure 3 As can be seen from the data, the electric field strength at the position below the stage of the detector with different thicknesses in Example 1 is greater than that at the position below the stage of the detector with different thicknesses in Comparative Example 1.

[0053] from Figure 4 As can be seen from the data, the photocurrent of the detector in Example 1 is greater than that of the detector in Comparative Example 1.

[0054] from Figure 5 As can be seen, the responsivity of the detector in Example 1 is greater than that of the detector in Comparative Example 1.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A GaN-based gradient-doped extreme ultraviolet detector, characterized in that, include: Substrate; A GaN buffer layer is located on the surface of the substrate; An n-GaN layer is located on the surface of the GaN buffer layer away from the substrate; The i-GaN layer is located on the surface of the n-GaN layer away from the substrate; The n-type electrode is located on the surface of the n-GaN layer away from the substrate, and the i-GaN layer and the n-type electrode are located on opposite sides of the surface of the n-GaN layer, respectively. A gradient-doped p-GaN layer is located on the surface of the i-GaN layer away from the substrate; The p-type electrode is located on the surface of the gradient-doped p-GaN layer away from the substrate; The doping concentration of the gradient-doped p-GaN layer gradually decreases from the surface of the gradient-doped p-GaN layer near the p-type electrode to the surface away from the p-type electrode.

2. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The doping concentration of the gradient-doped p-GaN layer varies from (2~3)×10⁻⁶ in the direction from the surface of the gradient-doped p-GaN layer near the p-type electrode to the surface away from the p-type electrode. 19 cm -3 Reduced to (1~2)×10 16 cm -3 .

3. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The thickness of the gradient-doped p-GaN layer is 50~150nm.

4. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The thickness of the n-GaN layer is ≥400 nm, and the doping concentration is ≥5 × 10⁻⁶. 18 cm -3 .

5. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The i-GaN layer is an unintentionally doped GaN layer, and the thickness of the i-GaN layer is 400~500nm.

6. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The substrate is a heterogeneous substrate or a homogeneous substrate; The heterogeneous substrate includes any one of sapphire substrate, silicon carbide substrate, and silicon substrate; The homogeneous substrate includes a GaN substrate or an AlN substrate.

7. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The material of the n-type electrode includes at least one of Pt, Ti, Ni, and Au; The material of the p-type electrode includes at least one of Ni, Pt, and Au.

8. The GaN-based gradient-doped extreme ultraviolet detector as described in claim 1, characterized in that, The thickness of the n-type electrode is 50~300 nm; The thickness of the p-type electrode is 3~5 nm; The thickness of the GaN buffer layer is 50~200 nm.

9. A method for fabricating a GaN-based gradient-doped extreme ultraviolet detector as described in any one of claims 1 to 8, characterized in that, Includes the following steps: A GaN buffer layer is epitaxially grown on the substrate surface; An n-GaN layer is deposited on the surface of the GaN buffer layer; An i-GaN layer is deposited on one side of the surface of the n-GaN layer; A gradient-doped p-GaN layer is deposited on the surface of the i-GaN layer; Etch the device mesa until the n-GaN layer is exposed; An n-type electrode is deposited on the surface of the n-GaN layer in the etched region below the mesa; A p-type electrode is deposited on the surface of the gradient-doped p-GaN layer.

10. The method for fabricating a GaN-based gradient-doped extreme ultraviolet detector as described in claim 9, characterized in that, Includes the following steps: A GaN buffer layer and an n-GaN layer are epitaxially grown sequentially on the substrate surface; i-GaN material and gradient-doped p-GaN material are grown on the surface of the n-GaN layer, and a SiO2 mask layer is grown on the outside of the gradient-doped p-GaN material. A mesa pattern is photolithographically etched on the SiO2 mask layer. The SiO2 mask layer that is not covered by photoresist in the non-mesa pattern area is etched away. The area not covered by the SiO2 mask layer is etched to the n-GaN layer. The SiO2 mask layer in the mesa area is removed to obtain the gradient-doped p-GaN layer and i-GaN layer. A photoresist mask pattern for an n-type electrode is prepared on top of an n-GaN layer using photolithography. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, n-type electrode material is deposited on the photoresist mask pattern. The photoresist and the electrode material covering it are then removed. Finally, annealing is performed to obtain the n-type electrode. A photoresist mask pattern for a p-type electrode is prepared on top of a gradient-doped p-GaN layer using photolithography. After development, the photoresist in the electrode pattern area is removed, while the photoresist in the non-electrode pattern area is retained. Then, p-type electrode material is deposited on the photoresist mask pattern, and the photoresist and the electrode material covering it are removed. Finally, annealing is performed to obtain the p-type electrode.

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