Micro-strip GaN n-i-n-i-p type X-ray detector and preparation method thereof

Abstract

The invention discloses a micro-strip GaN n-i-n-i-p type X-ray detector and a preparation method thereof, the detector structure sequentially comprises a substrate layer, a template layer and a doping layer, the doping layer is provided with a micro-strip unit, and the micro-strip unit sequentially comprises a multiplication layer, a drift layer, an absorption layer and an ohmic contact layer; the micro-strip units are arranged at intervals; a p-type ohmic electrode is also arranged on the doped layer; an n-type ohmic electrode is arranged on the ohmic contact layer; the ohmic contact layer is also provided with an n-type ohmic electrode and a groove structure; a passivation layer is also deposited on the outer surface of the detector; the plate layer, the multiplication layer and the absorption layer are all unintentionally doped GaN; the doping layer is p-type heavily-doped GaN, and the drift layer and the ohmic contact layer are n-type heavily-doped GaN; the preparation method is used for preparing the X-ray detector. The invention has the characteristics of high signal-to-noise ratio and low energy loss. The method can be widely applied to the field of semiconductor X-ray detection.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor X-ray detection, and in particular to a micro-strip GaN ninip type X-ray detector and a preparation method thereof. Background Art

[0002] X-ray detection technology has important applications in both military and civilian fields. Microstrip detectors are semiconductor detectors used to detect high-energy radiation. Silicon microstrip detectors, first proposed in the 1970s, are used in high-energy physics experiments due to their simple and low-cost fabrication process and their rapid response to irradiated particles. However, silicon microstrip detectors operate using a Schottky junction, which results in high leakage current under reverse bias, leading to increased noise and power consumption. Summary of the Invention

[0003] In view of this, in order to solve the technical problem of low signal-to-noise ratio caused by large reverse leakage current in existing microstrip detectors, in a first aspect, the present invention proposes a microstrip GaN ninip-type X-ray detector, which includes a substrate layer, a template layer, and a doping layer connected in sequence, wherein:

[0004] A microstrip unit is provided on the doping layer, and the microstrip unit includes a multiplication layer, a drift layer, an absorption layer and an ohmic contact layer in sequence; and there is a spacing between each microstrip unit;

[0005] A p-type ohmic electrode is also provided on the doping layer; an n-type ohmic electrode is provided on the ohmic contact layer; and the ohmic contact layer is also provided with an n-type ohmic electrode and a groove structure;

[0006] A passivation layer is also deposited on the outer surface of the detector.

[0007] In some embodiments, the materials of each layer are defined: the template layer, multiplication layer, and absorption layer are all unintentionally doped GaN; the doping layer is heavily p-type doped GaN; and the drift layer and ohmic contact layer are heavily n-type doped GaN.

[0008] Based on the structure of the above detector, the present invention also proposes a preparation method, which includes the following steps:

[0009] A template layer, a doping layer, a multiplication layer, a drift layer, an absorption layer, and an ohmic contact layer are sequentially deposited on a sapphire substrate using a metal organic compound chemical vapor deposition system;

[0010] Etching is performed using an ion device to etch the doping layer and the absorption layer at corresponding positions to form microstrip units and groove structures;

[0011] Depositing a layer of insulating material as a passivation layer on the surface of the substrate, and performing window opening to expose the ohmic contact region of the ohmic contact layer and the ohmic contact region of the doped layer;

[0012] The corresponding metal material is evaporated on the ohmic contact area of ​​the ohmic contact layer using an electron beam evaporation device. The device is then placed in a rapid annealing furnace, nitrogen is introduced, and annealed at 750°C for 30 seconds to obtain an n-type ohmic electrode.

[0013] The corresponding metal material is evaporated on the ohmic contact area of ​​the doped layer using electron beam evaporation equipment, and then the device is placed in a rapid annealing furnace, air is introduced, and annealed at 550°C for 10 minutes to obtain a p-type ohmic electrode.

[0014] Based on the above scheme, the present invention provides a micro-strip GaN ninip-type X-ray detector and a preparation method thereof. The grooves formed by etching into the absorption layer can effectively reduce the problem of dead zone energy loss; the band engineering design of the drift layer is introduced to achieve physical separation of the absorption region and the multiplication region and electric field gradient control, significantly improving the weak signal detection capability; the setting of the micro-strip spacing is not likely to generate crosstalk signals, while also being sufficient to capture two-dimensional information of particle motion; a passivation layer is deposited on the device surface to solve the leakage problem caused by the surface state of the device, while also reducing the possibility of premature breakdown caused by sidewall leakage channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of a micro-strip GaN ninip type X-ray detector of the present invention;

[0016] Figure 2 This is another structural schematic diagram of a micro-strip GaN ninip type X-ray detector of the present invention;

[0017] Figure 3 It is a flow chart of the steps of the preparation method of the present invention;

[0018] Figure numerals: 1, sapphire substrate layer; 2, template layer; 3, doping layer; 4, multiplication layer; 5, drift layer; 6, absorption layer; 7, ohmic contact layer; 8, passivation layer; 9, n-type ohmic electrode; 10, n-type ohmic electrode; 11, micro-strip spacing; 12, groove width. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] It should be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0021] It should be understood that the terms "system," "device," "unit," and / or "module" used in this application are a method for distinguishing different components, elements, parts, portions, or assemblies at different levels. However, if other terms can achieve the same purpose, the terms may be replaced by other expressions.

[0022] As used in this application and the claims, unless the context clearly indicates an exception, the terms "a," "an," "an," and / or "the" are not intended to refer to the singular and may include the plural, unless the context clearly indicates otherwise. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements. The phrase "comprises a..." does not preclude the presence of additional identical elements in the process, method, product, or apparatus that includes the elements.

[0023] In the description of the embodiments of this application, "plurality" refers to two or more than two. The terms "first" and "second" below are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0024] In addition, flow charts are used in this application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps may be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0025] Reference Figure 1 and Figure 2 , which is a schematic structural diagram of the micro-strip GaN ninip-type X-ray detector proposed in the present invention, comprises, from top to bottom, a sapphire substrate layer 1, a template layer 2, a doping layer 3, a multiplication layer 4, a drift layer 5, an absorption layer 6, an ohmic contact layer 7, and a passivation layer 8, wherein:

[0026] The template layer 2 is unintentionally doped GaN with a thickness of 2 μm; the doping layer 3 is p-type heavily doped GaN with a thickness of 0.3 μm; the multiplication layer 4 is unintentionally doped GaN with a thickness of 0.25 μm; the drift layer 5 is n-type heavily doped GaN with a thickness of 0.15 μm; the absorption layer 6 is unintentionally doped GaN with a thickness of 20 μm; the ohmic contact layer 7 is n-type heavily doped GaN with a thickness of 0.2 μm; and the passivation layer 8 is 2 μm of silicon dioxide.

[0027] The microstrip unit is composed of the multiplication layer 4, the drift layer 5, the absorption layer 6 and the ohmic contact layer 7. The width of the microstrip unit is 50 μm; the microstrip unit spacing is 25 μm;

[0028] In the ohmic contact layer, a low-power shallow etching technology is used to etch to the absorption layer to form a groove structure. The spacing of the groove structure is 10 μm; the width of the groove structure is 10 μm.

[0029] It also includes a p-type ohmic electrode 10 extending from the doping layer 3 and an n-type ohmic electrode 9 extending from the ohmic contact layer 7 .

[0030] The present invention introduces a NINIP absorption multiplication and separation structure to achieve low-noise hole multiplication, effectively improving the signal-to-noise ratio. It also utilizes a dead zone groove etching structure to achieve response collection of high-energy ray signals and effectively reduce energy loss of the detection target in the non-source area of ​​the detector surface.

[0031] like Figure 3 As shown, based on the structure of the above detector, a preparation method includes the following steps:

[0032] Step S1: using a metal organic chemical vapor deposition system to sequentially deposit a template layer, a doping layer, a multiplication layer, a drift layer, an absorption layer, and an ohmic contact layer on a sapphire substrate;

[0033] Step S2: using an inductively coupled plasma device to etch the doped layer and the absorption layer to form a groove structure and microstrip units; depositing a layer of insulating material on the substrate surface as a passivation layer, and opening windows to expose the ohmic contact areas of the n-type electrode and the p-type electrode;

[0034] Step S3: using an electron beam evaporation device to deposit titanium / aluminum / nickel / gold on the ohmic contact area of ​​the ohmic contact layer to a thickness of 20 / 100 / 50 / 40 nm, and then placing the device in a rapid annealing furnace, introducing nitrogen, and annealing at 750° C. for 30 seconds to obtain an n-type ohmic electrode;

[0035] Step S4: Use electron beam evaporation equipment to evaporate nickel / gold on the ohmic contact area of ​​the doped layer to a thickness of 30 / 30 nm, then place the sample in a rapid annealing furnace, let air in, and anneal at 550°C for 10 minutes to obtain a p-type ohmic electrode.

[0036] The contents of the above structural embodiments are all applicable to the present method embodiment. The functions specifically implemented by the present method embodiment are the same as those of the above structural embodiments, and the beneficial effects achieved are also the same as those achieved by the above structural embodiments.

[0037] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A micro-strip GaN ninip type X-ray detector, characterized in that: From bottom to top, it includes substrate layer, template layer and doping layer, among which: The doping layer is provided with a microstrip unit; The microstrip unit comprises, from bottom to top, a multiplication layer, a drift layer, an absorption layer and an ohmic contact layer; A p-type ohmic electrode is provided on the doping layer; An n-type ohmic electrode is provided on the ohmic contact layer; The ohmic contact layer is provided with a plurality of groove structures; A passivation layer is also deposited on the outer surface of the micro-strip GaN ninip type X-ray detector; The template layer is unintentionally doped GaN; the doping layer is p-type heavily doped GaN; the multiplication layer is unintentionally doped GaN, the drift layer is n-type heavily doped GaN, the absorption layer is unintentionally doped GaN, and the ohmic contact layer is n-type heavily doped GaN.

2. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The width of the micro strip unit is 50 μm, and the pitch between the micro strip units is 25 μm.

3. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The substrate is a sapphire substrate.

4. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The thickness of the template layer is 2 μm; the thickness of the doping layer is 0.3 μm.

5. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The thickness of the multiplication layer is 0.25 μm.

6. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The drift layer has a thickness of 0.15 μm.

7. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The absorption layer has a thickness of 20 μm.

8. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The thickness of the ohmic contact layer is 0.2 μm.

9. The micro-strip GaN ninip type X-ray detector according to claim 1, characterized in that: The width of the groove is 10 μm, and the pitch between the grooves is 10 μm.

10. A method for preparing a micro-strip GaN ninip type X-ray detector, characterized in that: include: A template layer, a doping layer, a multiplication layer, a drift layer, an absorption layer, and an ohmic contact layer are sequentially deposited on a sapphire substrate using a metal organic compound chemical vapor deposition system; Etching is performed using an ion device to etch the doped layer to form a microstrip unit; Etching to the absorption layer to form a groove structure; Depositing a layer of insulating material as a passivation layer on the surface of the substrate, and performing window opening to expose the ohmic contact region of the ohmic contact layer and the ohmic contact region of the doped layer; Using electron beam evaporation equipment to evaporate the corresponding metal material on the ohmic contact area of ​​the ohmic contact layer, and then placing the device in an annealing furnace, passing nitrogen gas, and performing annealing at a preset temperature and preset time to obtain an n-type ohmic electrode; The corresponding metal material is evaporated on the ohmic contact area of ​​the doped layer using electron beam evaporation equipment, and then the device is placed in an annealing furnace, air is introduced, and annealing is performed at a preset temperature and preset time to obtain a p-type ohmic electrode.

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