CN102496648A - Built-in Negative Feedback Metal-Semiconductor-Metal Structure UV Single Photon Detector - Google Patents

Abstract

A built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector, each detector includes a substrate from bottom to top, a buffer layer can be grown on the substrate, an n-type semiconductor is on the substrate or buffer layer, and the n-type semiconductor The upper layer is an interdigitated thin film resistor. The anode electrode is deposited on the thin film resistor to form an anode electrode. The uppermost layer is an interdigitated electrode. The cathode electrode forms a Schottky junction with the n-type semiconductor, and the anode electrode is deposited on the thin film resistor. The ultraviolet single photon detector with built-in negative feedback metal-semiconductor-metal structure of the present invention overcomes the problems of difficult process control and high cost caused by the complex process flow of the pn and pin structure ultraviolet single photon detectors.

Description

Built-in Negative Feedback Metal-Semiconductor-Metal Structure UV Single Photon Detector

technical field

The invention relates to a novel metal-semiconductor-metal structure ultraviolet single-photon detector and its manufacturing method, and the structure is also applicable to metal-semiconductor-metal structure single-photon detectors in other bands.

Background technique

The detection of ultraviolet light, especially the solar-blind ultraviolet band, has extremely important applications in space detection and military affairs. At present, the photon counting system in the ultraviolet band uses a photomultiplier tube (PMT), but the photomultiplier tube is large in size, fragile, high in operating voltage and expensive, so a solid-state ultraviolet detector with a small size and cheap price is very important. The advantages.

The currently available solid-state single-photon detectors in the ultraviolet band are p-n structures or p-i-n structures. Ohmic contact, the process is difficult to form a good ohmic contact, process control is difficult, and the preparation cost is extremely high.

Metal-semiconductor-metal (MSM) structure detectors (physics of semiconductor devices, third edition, S.M.Sze, Wiley Interscience) have no p-type semiconductor, small capacitance, and are easy to manufacture, so the MSM structure ultraviolet light detector has a high Value. As shown in Figure 1A, it is a typical MSM structure detector section view, MSM 100 structure detector is made up of substrate 101, n-type semiconductor 102 and interdigitated electrodes 103 and 104, and its front electrode structure is as shown in Figure 1B, The electrodes 103-1, 103-2..., 103-N form interdigitated cathode electrodes, and the electrodes 104-1, 104-2..., 104-N form interdigitated anode electrodes. Figure 1C is the equivalent circuit structure diagram of the MSM100 structure detector. The MSM 100 is composed of two back-to-back Schottky diodes. When the operating voltage is applied, a depletion layer is formed between the interdigitated electrodes, and photons in the depletion region It is absorbed to generate photoelectrons, and photoelectron migration or drift motion is collected by interdigitated electrodes to generate electrical signals, so that optical signals can be detected. The ultraviolet avalanche tube based on the MSM structure was also reported in 2011, (F.Xie, IEEE ELECTRONDEVICE LETTERS, VOL.32, NO.9, SEPTEMBER 2011). However, the traditional MSM structure detector needs an external complex quenching circuit to realize single photon detection, which increases the cost of system design.

Contents of the invention

The purpose of the present invention is to propose a novel MSM-based structure with built-in negative feedback ultraviolet light single photon detector structure and its manufacturing method.

The technical solution of the present invention is: a built-in negative feedback ultraviolet single photon detector structure based on the MSM structure, including a substrate, an n-type semiconductor, a thin film resistor and an interdigitated electrode; preferably, the ultraviolet single photon detector of the structure is obtained from From bottom to top, it includes the substrate, the n-type semiconductor, the cathode electrode and the n-type semiconductor to form a Schottky junction, the thin-film resistor is deposited on the n-type semiconductor, and the anode electrode is grown on the thin-film resistor.

The preparation method of the MSM structure ultraviolet single photon detector comprises the following steps:

(1) Form an n-type semiconductor on the substrate, or grow a multi-layer buffer layer before, and then grow an n-type semiconductor;

(2) Grow and etch a thin film resistor on the n-type semiconductor to form the shape of an interdigitated anode electrode;

(3) Deposit electrodes to form interdigitated cathode electrodes and anode electrodes.

As shown in FIG. 2E, the built-in negative feedback MSM structure ultraviolet single photon detector structure includes a substrate 201, an n-type semiconductor 202, a cathode electrode 204 deposited on the n-type semiconductor to form a Schottky contact, and a thin film resistor 203- 1, 203-2..., 203-N are deposited on the n-type semiconductor to form an interdigitated resistor, and the anode electrodes 205-1, 205-2..., 205-N are deposited on the thin film resistor 203 to form an anode electrode 205, fork Finger cathode 204, thin film resistor 203 and anode electrode 205 are shown in FIG. 2F. Wherein the electrodes 204 and 205 may be transparent metal materials.

The technological process of the ultraviolet single photon detector MSM 200 includes:

Step 1, as shown in FIG. 2A , depositing a buffer layer on the substrate to reduce the lattice fit between the substrate and the n-type semiconductor, thereby reducing the defect density, and forming a substrate 201;

Step 2, as shown in FIG. 2B, depositing an n-type semiconductor 202 on the substrate 201;

Step 3, as shown in FIG. 2C, depositing a thin film resistor 203 on the n-type semiconductor 202;

Step 4, as shown in FIG. 2D, etching the thin film resistor 203 to form interdigitated resistors 203-1, 203-2;

Step 5, as shown in FIG. 2E, deposit and form anode electrodes 205-1, 205-2 and cathode electrodes 204-1, 205-2, the cathode electrodes and n-type semiconductors form Schottky contacts, and the anode electrodes are deposited on the film on the resistor.

The equivalent circuit diagram of the ultraviolet single photon detector MSM 200 is shown in Figure 2F. When it is working, the Schottky junction formed by the cathode and n-type semiconductor in the MSM200 is reverse-biased, and the operating voltage exceeds its breakdown voltage, making the detector Working in Geiger Mode (Geiger Mode) [D.Renker, Nuclear Instruments and Methods in Physics Research A 567 (2006) 48-56], at this time a depletion layer is formed between the cathode 204 and the anode 205 of the detector MSM 200, depletion The electric field intensity in the depletion layer is extremely high. When there is no light, the Schottky junction in the detector MSM 200 is in the reverse bias state. The Schottky junction is equivalent to a capacitor, and the working voltage is mainly distributed on the Schottky upper junction. , if a photon reaches the depletion layer of the detector MSM 200, the photon is absorbed to generate electron-hole pairs, and the electrons and holes multiply in the depletion layer to generate more electrons and holes, and the reverse-biased Schottky junction An avalanche occurs, so that a photon signal is converted into an electrical signal and amplified. This process can be regarded as the discharge process of the capacitor. At this time, a large part of the operating voltage is distributed to the thin film resistor 203, so that the voltage on the Schottky junction decreases. , the avalanche is extinguished, and the thin film resistor 203 has a negative feedback effect. Once the voltage across the reverse-biased Schottky junction in the MSM 200 decreases, the avalanche process is extinguished, at which point the Schottky junction is recharged and the voltage increases, enabling detection of the next optical signal.

Due to the complex process of p-n structure or p-i-n structure ultraviolet avalanche tube, it is necessary to grow n-type semiconductor and p-type semiconductor, and it is difficult to control the defect density of GaN and AlGaN-based materials. Ohmic contact needs to be formed between them, and this is also a process step that is extremely difficult to control in the process.

However, the built-in negative feedback ultraviolet single photon detector MSM 200 based on the metal-semiconductor-metal structure only needs to grow an n-type semiconductor, and at the same time, a Schottky contact is formed between the electrode and the semiconductor, so the requirements for the electrode process are simple and the cost is low. Inexpensive, and the capacitance of the MSM structure is small, so the response speed of the MSM 200 UV single photon detector is relatively fast. And in the MSM 200 ultraviolet single photon detector, because of the built-in thin film resistor 203, when the MSM 200 detects a light signal, the avalanche current caused by it can be extinguished by the thin film resistor, so that the next light signal can be detected. The MSM 200 single photon detector has a built-in negative feedback function and does not require the assistance of an external complex extinguishing circuit, thereby reducing the design cost of the entire MSM 200 single photon detector system.

The MSM 200 ultraviolet single photon detector works in Geiger Mode, and its working voltage is between 10V-200V.

In the MSM 200 ultraviolet single photon detector, the n-type semiconductor is made of III-V group material, II-VI group material or IV-IV group material.

In the preparation process of the MSM 200 ultraviolet single photon detector, n-type semiconductors and thin film resistors can be prepared by MOCVD process.

The beneficial effects of the present invention are: the built-in negative feedback metal-semiconductor-metal structure ultraviolet single photon detector of the present invention overcomes the process control difficulty and cost caused by the complex process flow of p-n and p-i-n structure ultraviolet single photon detectors expensive problem. The ultraviolet single photon detector with built-in negative feedback metal-semiconductor-metal structure of the present invention overcomes the difficulty that traditional MSM structure detectors need to be externally connected with complex extinguishing circuits, simplifies system design, and reduces design cost.

Description of drawings

Fig. 1A is the sectional view of typical metal-semiconductor-metal ultraviolet photodetector;

Fig. 1B is a front electrode structure diagram of a typical metal-semiconductor-metal ultraviolet photodetector;

Fig. 1C is a typical metal-semiconductor-metal ultraviolet photodetector equivalent circuit diagram;

Fig. 2A is a schematic diagram of the substrate in the fabrication process of the built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector;

Fig. 2B is a schematic diagram of depositing n-type semiconductor during the preparation process of built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector;

Fig. 2C is a schematic diagram of deposited thin film resistance during the preparation process of built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector;

Figure 2D is a schematic diagram of etching thin film resistance during the fabrication process of built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector;

Figure 2E is a schematic diagram of electrodes deposited and formed during the fabrication process of built-in negative feedback metal-semiconductor-metal ultraviolet single photon detectors and a cross-sectional view of the detectors;

Fig. 2F is a structure diagram of the front thin film resistance and electrodes of the built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector;

Fig. 2G is an equivalent circuit diagram of a built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector.

specific implementation plan

As shown in Figure 2E, it is a cross-sectional structure diagram of the built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector of the present invention, we can form the substrate 201 from bottom to top, and the substrate 201 can be SiC, sapphire and silicon, etc. The material can also be GaN-based or AlGaN-based materials; n-type semiconductor 202, the material can be GaN, AlGaN and SiC and other materials, which also has a buffer layer to reduce lattice adaptation and reduce dislocation density, and MOCVD epitaxy can be used Growth; thin film resistor 203, the thin film resistor can be SiC, _Six O _y or undoped GaN, AlGaN and other materials, its resistance value is about tens of KΩ to 1MΩ, and can be epitaxially grown by MOCVD; cathode electrode 204 and The anode electrode 205 and the cathode electrode 204 form a Schottky junction with the n-type semiconductor, and the electrodes can be made of transparent or translucent materials.

The built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector of the present invention is based on the metal-semiconductor-metal detector structure, which has the advantages of simple process and low cost. - metal ultraviolet light single photon detector, its specific process steps are:

A buffer layer can be deposited on the substrate 201 to reduce lattice adaptation and defect density. The substrate 201 can be made of materials such as SiC, sapphire and silicon, or GaN-based or AlGaN-based materials, as shown in Figure 2A shown;

Deposit an n-type semiconductor 202 on the substrate 201, which can be GaN, AlGaN-based material, or SiC material, and its thickness is 1-10 μm. The n-type semiconductor can be grown by MOCVD, as shown in FIG. 2B; buffer layer It is the same layer material grown at low temperature in GaN, AlGaN based material (see applicant's patent application.)

Deposit a thin film resistor 203 on the n-type semiconductor 202, which can be SiC, Six _{O y} or undoped GaN, AlGaN and other materials, and its resistance value is about tens of KΩ to 1MΩ, as shown in Figure 2C;

Etching the thin film resistor 203 into an interdigitated structure, each of which has a width of 10 μm and a spacing of 30 μm, as shown in FIG. 2D ;

The electrode can be grown by PECVD, so that the cathode electrode 204 is in the middle of the interdigitated thin film resistor 203, the width of the cathode electrode 204 is 10 μm, and the cathode electrode forms a Schottky contact with the n-type semiconductor, so that the anode electrode 205 is grown between the thin film resistor 203 , the electrode width is 10 μm, as shown in Figure 2E, and its interdigitated electrodes and sheet resistance are shown in Figure 2F.

The built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector MSM 200 of the present invention works in Geiger mode (Geiger Mode), that is, a negative bias is applied, and the applied voltage exceeds the breakdown voltage of the detector. Its magnitude is about 10V-20V. When there is no light, the detector MSM 200 cannot undergo avalanche breakdown, and the current measured on the electrode is very small; when there is light, the detector MSM 200 undergoes avalanche breakdown, and the electrode A large current is detected, which is an electrical signal, and the built-in thin-film resistor can extinguish the avalanche, so that the detector MSM 200 can continue to detect optical signals. The embodiment is sensitive to ultraviolet light with a wavelength of 0.2-0.3 microns. It is a conventional method to form an array of ultraviolet light single photon detectors of the present invention.

Claims (8)

1. A built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector is characterized in that each detector includes a substrate from bottom to top, a buffer layer can be grown on the substrate, and the substrate or buffer layer is n-type Semiconductor, on the n-type semiconductor is an interdigitated thin film resistor, the anode electrode is deposited on the thin film resistor to form an anode electrode, the uppermost layer is an interdigitated electrode, the cathode electrode forms a Schottky junction with the n-type semiconductor, and the anode electrode is deposited on the on the thin film resistor. 2. The built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector as claimed in claim 1 is characterized in that the etching thin film resistor (203) becomes an interdigitated structure, and each interdigit width is 10 μm, and the spacing is 30 μm; the cathode electrode is in the middle of the interdigitated thin film resistor 203, and the width of the cathode electrode is 10 μm. The cathode electrode forms a Schottky contact with the n-type semiconductor, so that the anode electrode 205 grows on the thin film resistor, and the electrode width is 10 μm. 3. The substrate of the built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector as claimed in claim 1 or 2 is selected from materials such as SiC, GaN, sapphire or silicon. 4. The n-type semiconductor of the built-in negative feedback metal-semiconductor-metal ultraviolet single photon photon detector as claimed in claim 1 or 2 can be materials such as SiC, GaN, AlGaN bases. 5. The built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector as claimed in claim 1 or 2 works under negative bias voltage, which exceeds the breakdown voltage of the detector, and the voltage is 10V-20V. 6. The built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector mechanism as described in one of claims 1 to 4 is suitable for the detection of visible light, infrared light and other wave bands, and its n-type semiconductor can be other III- Group V or II-VI materials. 7. the preparation step of built-in negative feedback metal-semiconductor-metal ultraviolet light single photon detector according to claim 1 is: (1) Deposit a buffer layer on the substrate to reduce lattice mismatch and defect density; (2) Deposit n-type semiconductor on the substrate; (3) Deposit thin film resistors on the n-type semiconductor and etch them into interdigitated shapes; (4) Deposit interdigitated electrodes, the cathode electrode and the n-type semiconductor form a Schottky junction, and the anode electrode is on the thin film resistor. 8. The preparation step of the built-in negative feedback metal-semiconductor-metal ultraviolet single photon detector according to claim 1 is: depositing a thin film resistor 203 on the n-type semiconductor 202, which is SiC, _Six O _y or undoped Doped GaN, AlGaN material, its resistance value is about tens of KΩ to 1MΩ.

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