Broadband ultraviolet detector based on semi-polar superlattice structure and preparation method thereof
阅读说明：本技术 基于半极性超晶格结构的宽波段紫外探测器及其制备方法 (Broadband ultraviolet detector based on semi-polar superlattice structure and preparation method thereof ) 是由 徐峰 于 2021-07-06 设计创作，主要内容包括：本发明公开了一种基于半极性超晶格结构的宽波段紫外探测器及其制备方法,所述紫外探测器包括衬底、生长在衬底上的薄膜层、淀积在薄膜层的掩膜层、以及生长在掩膜层上的光吸收层、以及复合于光吸收层上的电极层；所述光吸收层为半极性AlInGaN超晶格材料。本发明将低缺陷密度的半极性Al-(x)Ga-(1-x)N/In-(y)Ga-(1-y)N超晶格结构成功应用于紫外探测器吸收层,同时可以通过精确调节金属Al、In金属元素组分x和y,使Al-(x)In-(y)Ga-(1-x-y)N超晶格材料带隙宽度在3.4～6.2eV范围连续可调,对应的响应波长范围处于200～365nm。本发明的紫外探测器能够兼顾降低材料缺陷密度和极化效应,结合金属叉指结构电极工艺,能有效提高光生载流子收集效率,在降低器件暗电流的同时,显著提高响应度和响应速度。(The invention discloses a broadband ultraviolet detector based on a semi-polar superlattice structure and a preparation method thereof, wherein the ultraviolet detector comprises a substrate, a thin film layer grown on the substrate, a mask layer deposited on the thin film layer, a light absorption layer grown on the mask layer and an electrode layer compounded on the light absorption layer; the light absorption layer is made of a semi-polar AlInGaN superlattice material. The invention combines low defect density semipolar Al x Ga 1‑x N/In y Ga 1‑y The N superlattice structure is successfully applied to the ultraviolet detector absorption layer, and meanwhile, the metal components x and y of metal Al and In can be accurately adjusted to ensure that Al is In a pure state x In y Ga 1‑x‑y The band gap width of the N superlattice material is continuously adjustable within the range of 3.4-6.2 eV, and the corresponding response wavelength range is 200-365 nm. The ultraviolet detector can reduce the defect density and polarization effect of materials, combines a metal interdigital structure electrode process, can effectively improve the collection efficiency of photon-generated carriers, and obviously improves the responsiveness and response speed while reducing the dark current of a device.)
1. A broadband ultraviolet detector based on a semi-polar superlattice structure is characterized by comprising a substrate, a thin film layer grown on the substrate, a mask layer deposited on the thin film layer, a light absorption layer grown on the mask layer, and an electrode layer compounded on the light absorption layer; the light absorption layer is made of a semi-polar AlInGaN superlattice material. The AlInGaN superlattice material is AlxGa1-xN/InyGa1-yThe N-type superlattice structure comprises an Al component x with a change range of 0-1, an In component y with a change range of 0-1, and x/y with a value of 4.66.
2. The broadband ultraviolet detector based on the semi-polar superlattice structure according to claim 1, wherein the substrate is a sapphire substrate or a silicon substrate.
3. The broadband ultraviolet detector based on the semi-polar superlattice structure according to claim 1, wherein the thin film layer is a GaN thin film layer, the electrode layer is a Ni/Au double-layer MSM metal electrode layer, and the mask layer isSiO2Mask layer or Si3N4And (5) masking the layer.
4. The broadband ultraviolet detector based on the semi-polar superlattice structure according to claim 1, wherein Al isxGa1-xN/InyGa1-yThe N superlattice structure contains N AlxGa1-xN sublayers and N InyGa1-yN sublayers; wherein, AlxGa1-xThe N sublayer is a semipolar crystal face with a thickness of not less than 0.1nm InyGa1-yThe N sublayer is a semipolar crystal face, and the thickness is not less than 0.1 nm.
5. The broadband ultraviolet detector based on the semi-polar superlattice structure according to claim 1, wherein Al isxGa1-xN/InyGa1-yThe number of superlattice structure periods of N is not less than 1.
6. The broadband ultraviolet detector based on the semi-polar superlattice structure according to any one of claims 1-5, characterized in that the adjustable range of the band gap width of the AlInGaN superlattice material is 3.4-6.2 eV, and the response wavelength of the ultraviolet detector is 200-365 nm.
7. A preparation method of a broadband ultraviolet detector based on a semi-polar superlattice structure is characterized by comprising the following steps:
(1) epitaxially growing a thin film layer on the substrate by using a chemical vapor deposition method, or directly adopting a self-supporting substrate material with the thin film layer; then, a mask layer is deposited on the thin film layer by utilizing a plasma enhanced chemical vapor deposition method;
(2) utilizing photoetching and wet etching methods to open a cross-shaped groove window along the semi-polar crystal direction of the thin film layer on the mask layer to expose the thin film layer;
(3) carrying out secondary epitaxial growth on the film with the growth mask pattern by using a chemical vapor deposition method to obtain a semipolar AlGaN/InGaN superlattice structure;
(4) and forming a metal electrode layer on the surface of the semi-polar AlGaN/InGaN superlattice structure by using an electron beam evaporation method, and then performing rapid thermal annealing in a nitrogen atmosphere to form Schottky contact so as to obtain the ultraviolet detector.
8. The method for preparing a broadband ultraviolet detector based on a semi-polar superlattice structure as claimed in claim 7, wherein the chemical vapor deposition method in the steps (1) and (3) is a metal organic chemical vapor deposition method based on selective lateral epitaxy.
9. The method for preparing the broadband ultraviolet detector based on the semi-polar superlattice structure is characterized in that the substrate is a sapphire substrate or a silicon substrate; the film layer is a GaN film layer, the metal electrode layer is a Ni/Au double-layer MSM metal electrode layer, and the mask layer is SiO2Mask layer or Si3N4And (5) masking the layer.
Technical Field
The invention relates to a semiconductor device and a preparation method thereof, in particular to a broadband ultraviolet detector based on a semi-polar superlattice structure and a preparation method thereof.
Background
The broadband ultraviolet detection technology has extremely important application in the fields of ultraviolet communication, reconnaissance and early warning, environmental pollution monitoring and the like. The AlGaN-based third-generation wide bandgap semiconductor material has physicochemical properties of high electron saturation velocity, high breakdown electric field, high thermal conductivity, radiation resistance and the like, and thus becomes a preferred material system for preparing an ultraviolet detector. The detection wavelength can be continuously adjustable within the range of 200-365 nm by adjusting the material components of AlGaN, and the AlGaN optical fiber is very suitable for distinguishing and monitoring solar blind ultraviolet broad bands under the background of visible light. The AlGaN-based metal-semiconductor-metal (MSM) structure detector is one of the most focused ultraviolet detectors at present due to its advantages of small capacitance, simple structure, high responsivity, high ultraviolet detection ratio, and the like.
Although the AlGaN ultraviolet detector has the advantages, high-density dislocation defects are introduced into an AlGaN material based on lattice mismatch and thermal mismatch caused by heteroepitaxial growth, so that the thickness of a Schottky barrier is thinned, and defect-assisted tunneling current is formed, thereby increasing the dark current of the detector.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a broadband ultraviolet detector based on a semi-polar superlattice structure, which has the advantages of high response speed, high detection efficiency, low dark current and good device performance; the invention also aims to provide a preparation method of the broadband ultraviolet detector based on the semi-polar superlattice structure.
The technical scheme is as follows: the invention relates to a broadband ultraviolet detector based on a semi-polar superlattice structure, which comprises a substrate, a thin film layer grown on the substrate, a mask layer deposited on the thin film layer, a light absorption layer grown on the mask layer, and an electrode layer compounded on the light absorption layer; the light absorption layer is made of a semi-polar AlInGaN superlattice material; the AlInGaN superlattice material is AlxGa1-xN/InyGa1-yA N superlattice structure, wherein the composition x of Al is changedThe range is 0-1, the variation range of the In component y is 0-1, and the x/y is 4.66.
Preferably, the substrate is a sapphire substrate or a silicon substrate.
Preferably, the thin film layer is a GaN thin film layer, the electrode layer is a Ni/Au double-layer MSM metal electrode layer, and the mask layer is SiO2Mask layer or Si3N4And (5) masking the layer.
Preferably, AlxGa1-xN/InyGa1-yThe N superlattice structure contains N AlxGa1-xN sublayers and N InyGa1-yN sublayers; wherein, AlxGa1-xThe N sublayer is a semipolar crystal face with a thickness of not less than 0.1nm InyGa1-yThe N sublayer is a semipolar crystal face, and the thickness is not less than 0.1 nm.
Preferably, AlxGa1-xN/InyGa1-yThe number of superlattice structure periods of N is not less than 1.
Semipolar AlxGa1-xN/InyGa1-yThe N-type superlattice structure is composed of semipolar AlxGa1-xN and InyGa1-yN superlattice sublayers. Growing AlxGa1-xN/InyGa1-yIn the case of an N superlattice structure, since the sub-layers are shared by the upper and lower layers to distribute the components uniformly, an AlInGaN superlattice material having an In-plane lattice constant between AlGaN and InGaN can be finally formed, and when the ratio of the metal element components x and y of Al and In is 4.66, complete matching with the In-plane lattice constant of GaN can be realized.
Preferably, the adjustable range of the band gap width of the AlInGaN superlattice material is 3.4-6.2 eV, and the response wavelength of the ultraviolet detector is 200-365 nm. By adjusting the component ratio x/y of Al and In metal elements, the adjustable range of the band gap width of the AlInGaN superlattice material can be 3.4-6.2 eV, and the response wavelength of a corresponding ultraviolet detector is 200-365 nm.
The preparation method of the broadband ultraviolet detector comprises the following steps:
(1) epitaxially growing a thin film layer on the substrate by using a chemical vapor deposition method, or directly adopting a self-supporting substrate material with the thin film layer; then, a mask layer is deposited on the thin film layer by utilizing a plasma enhanced chemical vapor deposition method;
(2) utilizing photoetching and wet etching methods to open a cross-shaped groove window along the semi-polar crystal direction of the thin film layer on the mask layer to expose the thin film layer;
(3) carrying out secondary epitaxial growth on the film with the growth mask pattern by using a chemical vapor deposition method to obtain a semipolar AlGaN/InGaN superlattice structure;
(4) and forming a metal electrode layer on the surface of the semi-polar AlGaN/InGaN superlattice structure by using an electron beam evaporation method, and then performing rapid thermal annealing in a nitrogen atmosphere to form Schottky contact so as to obtain the ultraviolet detector.
Further, the chemical vapor deposition method in the step (1) and the step (3) is a metal organic chemical vapor deposition method based on a selective lateral epitaxy method.
Further, the substrate is one or more of a sapphire substrate, an indium tin oxide substrate, a quartz substrate and a magnesium oxide substrate; the film layer is a GaN film layer, the metal electrode layer is a Ni/Au double-layer MSM metal electrode layer, and the mask layer is SiO2Mask layer or Si3N4And (5) masking the layer.
The mask layer is SiO2Mask layer or Si3N4The mask layer is based on a selective transverse epitaxial growth quality transport mechanism, the type of the semipolar surface mainly depends on the surface energy and surface atomic stability of the crystal face, and when strip-shaped, cross-shaped and other secondary epitaxial growth windows of the mask layer are along the specific semipolar crystal direction of the GaN film layer, AlGaN and InGaN superlattice sublayer film materials with the morphology of the micro-surface being the semipolar crystal face can be grown and obtained.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
(1) the performance parameters of the ultraviolet detector reach the following indexes: v-shaped defect density on surface of superlattice material<4.6×105/cm2Surface roughness RMS<1 nm; secondly, detecting the dark current of the device to be lower than 1 pA; third, the internal quantum efficiency of the detector>80％；
(2) Dark current and photoconductive gain of the detection device are effectively reduced, lattice matching with the GaN layer can be realized by the AlGaN/InGaN superlattice structure, so that stress caused by lattice mismatch is effectively eliminated, and a fill-in factor of a growth mask layer is further optimized;
(3) the defect density of the material is reduced, and most dislocation lines can be deflected by 90 degrees at a semipolar interface by the selective lateral epitaxy process, so that the dislocation density of the material is reduced.
Drawings
FIG. 1 is a schematic structural view of an ultraviolet detector in example 1;
FIG. 2 is a schematic view of the structure of a semipolar AlGaN/InGaN superlattice in example 1;
FIG. 3 is a schematic structural view of an AlGaN/InGaN superlattice in an ultraviolet detector of example 1;
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
Example 1
1. Ultraviolet detector
As shown in fig. 1, a broadband ultraviolet detector based on a semipolar superlattice structure includes a substrate 1, a thin film layer 2 grown on the substrate 1, a mask layer 3 deposited on the thin film layer 2, a light absorbing layer 4 grown on the mask layer 3, and an electrode layer 5 composited on the light absorbing layer 4.
The substrate 1 is a sapphire substrate, the thin film layer 2 is a GaN thin film layer, and the mask layer 3 is SiO2The mask layer is formed by a semi-polar AlGaN/InGaN superlattice material in the light absorption layer 4 and a Ni/Au double-layer MSM metal electrode layer in the electrode layer 5.
As shown in fig. 2, the structure of the semipolar AlGaN/InGaN superlattice is schematically illustrated, and an InGaN layer 41, an AlGaN layer 42, an InGaN layer 43, an AlGaN layer 44, an InGaN layer 45, and an AlGaN layer 46 are sequentially disposed on the GaN thin film layer. Fig. 2 only illustrates the structural relationship between the InGaN layer and the AlGaN layer, the number of the InGaN layer and the AlGaN layer is greater than the number of layers in the picture, and the AlGaN/InGaN superlattice structure includes n AlGaN sublayers and n InGaN sublayers.
As shown in FIG. 3, the structure of AlGaN/InGaN superlattice in ultraviolet detector is schematically shown, and the substrate 1 is sapphireThe substrate, the film layer 2 is a GaN film layer, and the mask layer 3 is SiO2The mask layer and the light absorption layer 4 are made of a semipolar AlGaN/InGaN superlattice material, wherein the mask layer 3 blocks a large number of dislocation lines generated by heteroepitaxy, and the dislocation lines 6 extending upwards in the growth window area can deflect at a semipolar interface, so that the dislocation density of the material is reduced.
2. The preparation method of the ultraviolet detector comprises the following steps:
(1) the chemical vapor deposition method adopts a planetary 4-inch metal organic chemical vapor deposition MOCVD preparation system, and utilizes the MOCVD system to epitaxially grow a GaN film layer on a sapphire substrate, wherein trimethyl gallium (TMGa) is an MO growth source of gallium; trimethylaluminum (TMAl) is an MO growth source of aluminum element, an MO growth source of trimethylindium (TMIn) indium element; the nitrogen source is ammonia (NH)3) (ii) a And then depositing a silicon dioxide mask layer on the GaN thin film layer by using a Plasma Enhanced Chemical Vapor Deposition (PECVD) method.
(2) Utilizing photoetching and wet etching methods to open a cross-shaped groove window along the GaN semipolar crystal direction on the silicon dioxide mask layer to expose the GaN thin film layer;
(3) performing secondary MOCVD epitaxy on the GaN film with the growth mask pattern to obtain a semi-polar AlGaN/InGaN superlattice structure;
(4) a Ni/Au double-layer MSM metal electrode is formed through an electron beam evaporation process, and then rapid thermal annealing is carried out at 700 ℃ in a nitrogen atmosphere to form Schottky contact, so that the preparation of the semi-polar AlGaN/InGaN superlattice structure MSM ultraviolet detection device is completed.
Example 2
1. Ultraviolet detector
The substrate is a silicon substrate, the film layer is a GaN film layer, and the mask layer is Si3N4The mask layer is made of a semipolar AlGaN/InGaN superlattice material, and the electrode layer is a Ni/Au double-layer MSM metal electrode layer.
2. The preparation method of the ultraviolet detector comprises the following steps:
(1) the chemical vapor deposition method adopts a planetary 4-inch metal organic chemical vapor deposition MOCVD preparation system, and utilizes the MOCVD systemEpitaxially growing a GaN film layer on a silicon substrate, wherein trimethyl gallium (TMGa) is an MO growth source of gallium; trimethylaluminum (TMAl) is an MO growth source of aluminum element, an MO growth source of trimethylindium (TMIn) indium element; the nitrogen source is ammonia (NH)3) (ii) a Then depositing Si on the GaN thin film layer by using Plasma Enhanced Chemical Vapor Deposition (PECVD)3N4And (5) masking the layer.
(2) By photolithography and wet etching on Si3N4A cross-shaped groove window along the GaN semipolar crystal direction is formed in the mask layer, and the GaN thin film layer is exposed;
(3) performing secondary MOCVD epitaxy on the GaN film with the growth mask pattern to obtain a semi-polar AlGaN/InGaN superlattice structure;
(4) a Ni/Au double-layer MSM metal electrode is formed through an electron beam evaporation process, and then rapid thermal annealing is carried out at 700 ℃ in a nitrogen atmosphere to form Schottky contact, so that the preparation of the semi-polar AlGaN/InGaN superlattice structure MSM ultraviolet detection device is completed.
The MOCVD selective lateral epitaxy process in the above embodiment uses silicon dioxide (or silicon nitride, etc.) with a cross-shaped groove structure as a growth mask layer, the growth mask layer blocks a large number of dislocation lines generated by heteroepitaxy, and simultaneously dislocation lines extending upwards in a growth window region can deflect at a semipolar interface to reduce density.
The invention combines low defect density semipolar AlxGa1-xN/InyGa1-yThe N superlattice structure is successfully applied to the ultraviolet detector absorption layer, and meanwhile, the metal components x and y of metal Al and In can be accurately adjusted to ensure that Al is In a pure statexInyGa1-x-yThe band gap width of the N superlattice material is continuously adjustable within the range of 3.4-6.2 eV, and the corresponding response wavelength range is 200-365 nm.
Wherein, AlxInyGa1-x-yBand gap width E of N materialgThe solution can be found as follows:
wherein the respective band bending parameters b of AlGaN and InGaN materialsAlGaN、bInGaNB can be obtained by quadratic approximation from 0.7eV and 2.1eV, respectivelyxy≈1eV。
The invention relates to reasonably designed semipolar AlxGa1-xN/InyGa1-yThe N superlattice structure broadband ultraviolet detector can reduce both material defect density and polarization effect, is combined with a metal interdigital structure electrode process, can effectively improve the collection efficiency of photon-generated carriers, and obviously improves the responsiveness and response speed while reducing the dark current of a device.
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