A cascaded dual-color photodetector based on avalanche effect to realize optical signal amplification

Abstract

This invention discloses a cascaded dual-color photodetector based on the avalanche effect for optical signal amplification, belonging to the field of photoelectric detection and photoelectric imaging technology. The invention designs a top-down semiconductor double heterojunction structure, inducing mutual excitation between a PIN-type infrared photodetector and a solar-blind ultraviolet avalanche photodetector through bias voltage modulation, achieving rapid detection of ultraviolet and infrared light incident on the detector. In this way, the invention overcomes the limitation of the absorption wavelength range of traditional detectors, enabling simultaneous detection of ultraviolet and infrared optical signals within the target environment, while improving the photocurrent gain for infrared optical signal detection. This invention is applicable to the field of photoelectric detection, enhancing the detection capability of target light and improving photoresponse.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic devices, and more particularly to a cascaded dual-color photodetector that amplifies optical signals based on the avalanche effect, belonging to the field of photoelectric detection. Background Technology

[0002] A photodetector is a detector that converts light signals into electrical signals, commonly used for detection in the ultraviolet, visible, and infrared bands. In the real environment, ultraviolet radiation mainly comes from the sun, with a wavelength range of 10-400nm. Ultraviolet light in the 100-280nm wavelength range has weak penetrating power and is absorbed by the ozone layer when passing through the atmosphere; therefore, there is almost no solar radiation from this band in the Earth's environment, known as the solar-blind ultraviolet region. Infrared radiation comes from the blackbody radiation of objects, with a wavelength range of 780nm-1mm. This band is sensed by heat and detected by special detectors or cameras. Infrared light in nature is roughly divided into three bands: near-infrared (780nm-2500nm), mid-infrared (2500nm-25μm), and far-infrared (25μm-500μm). According to Planck's law of blackbody radiation, objects at different temperatures emit different amounts of infrared light energy; this principle can be used to achieve infrared detection technology. Ultraviolet and infrared light cannot be observed by the human eye, but they provide important information in target detection. Therefore, with the advancement of semiconductor photoelectric detection technology, scientists have conducted in-depth research on ultraviolet and infrared light detection and have now developed a variety of single-band photoelectric detectors that can meet different scenarios and needs.

[0003] Based on current mature photoelectric detection technologies, photomultiplier tubes and GaN-based photoconductive detectors can already achieve ultraviolet detection in the 0.1-0.38nm wavelength range, while a-Ga2O3-based ultraviolet detectors can detect solar-blind wavelengths. Infrared detection has achieved detection in the 0.78-300μm wavelength range, such as HgCdTe mid-infrared photodetectors and InGaAs PIN photodiode near-infrared detectors. In recent years, improvements in semiconductor material growth and fabrication processes have led to the emergence of novel photoelectric detectors, such as van der Waals heterojunction-based photodetectors and quantum dot detectors, attracting numerous researchers. Semiconductor photoelectric detectors for detecting ultraviolet and infrared light have been widely applied in various civilian and military fields, including terrain monitoring, environmental monitoring, missile early warning, and space positioning. The substantial application demands have spurred the rapid development of infrared and ultraviolet monochromatic photoelectric detection technologies in their respective fields.

[0004] However, the development of infrared and ultraviolet detection technologies faces their respective limitations. In the military field, ultraviolet warning systems significantly reduce false alarms due to their unique "solar blindness" characteristic, but they suffer from low sensitivity and short detection range. Infrared detection technology, while possessing long-distance detection capabilities, is susceptible to external climate and temperature changes, leading to decreased detection stability. With the rapid advancement of modern science and technology, the performance requirements for photoelectric detectors in various fields are increasing, and single-band photoelectric detection technology can no longer meet these demands.

[0005] In summary, to enhance environmental adaptability, enable multi-scenario applications, and significantly increase the amount of information obtained by the detection system, developing more advanced dual-color and multi-color detection technologies has become one of the important development directions for ultraviolet and infrared photoelectric detection technologies. Summary of the Invention

[0006] Based on existing photoelectric detection technology and considering the band structure and material properties of semiconductors capable of detecting infrared and ultraviolet wavelengths, this invention proposes a cascaded dual-color photodetector that amplifies optical signals based on the avalanche effect. The aim is to overcome the limitation of traditional detectors in absorbing light wavelengths, enabling simultaneous detection of ultraviolet and infrared optical signals within the target environment, while simultaneously improving the photocurrent gain for infrared signal detection.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] Step 1: Fabricate a semiconductor heterojunction for an infrared photodetector structure;

[0009] The semiconductor structure for detecting infrared signals, from top to bottom, consists of n-InP / InGaAs / p-InP / p-InGaAs thin films. The InGaAs / InP structure is a mature infrared detector structure. This structure is prepared by epitaxial growth and can achieve absorption of infrared light near the 1550nm band.

[0010] Step 2: An ITO film is grown on the upper surface of the n-InP film on the infrared photodetector structure using magnetron sputtering technology;

[0011] Step 3: Grow an a-Ga2O3 film on the surface of an ITO film using magnetron sputtering.

[0012] Step 4: Deposit Ti / Au electrodes on the surfaces of n-InP and a-Ga2O3 films using magnetron sputtering.

[0013] The above steps complete the realization of an ultraviolet-infrared cascaded dual-color photodetector based on the avalanche effect to amplify optical signals. The basic design principle of this invention is as follows:

[0014] Based on the photovoltaic effect and band structure theory of semiconductor materials, and combined with the structural characteristics of infrared photodetectors and solar-blind ultraviolet avalanche photodetectors, a semiconductor heterostructure with a top-to-bottom structural distribution of a-Ga2O3 / ITO / InP / InGaAs was designed.

[0015] The ultraviolet detection structure is an a-Ga₂O₃ / ITO heterojunction: the a-Ga₂O₃ material has a bandgap of 5.3 eV, which allows it to absorb light signals near the 254 nm wavelength. The a-Ga₂O₃ film and the ITO film form a semiconductor heterojunction for detecting solar-blind ultraviolet signals. When the reverse bias voltage applied across the heterojunction exceeds the critical voltage, an avalanche photoelectric effect is triggered. ITO is an important transparent conductive optical material with a high carrier concentration, which gives the ITO film good conductivity. Simultaneously, the ITO material has a bandgap of 3.5 eV, providing high ultraviolet cutoff capability. Based on these material properties, the ITO thin film... In this invention, the film participates in the construction of the heterojunction of the solar-blind ultraviolet avalanche photodetector. At the same time, it serves as a transition layer between the infrared and ultraviolet detectors in the device, absorbing ultraviolet light and transmitting infrared light. This effectively prevents ultraviolet light from passing through the upper structure to excite the InGaAs / InP semiconductor heterojunction and generate signal crosstalk. The InGaAs / InP detector used for detecting infrared signals is a relatively mature application. Its narrow bandwidth characteristics make it highly efficient in detecting infrared light in the 1100nm-1700nm band, especially in the critical 1550nm band, which is basically the only choice at present. At the same time, the infrared detector with the InGaAs / InP heterojunction structure has the advantage of being able to operate under uncooled conditions.

[0016] Structurally, this photodetector can be considered a dual-color photodetector composed of a solar-blind ultraviolet avalanche detector and a PIN infrared photodetector cascaded together. During operation, a reverse bias voltage is applied across the detector, the value required to bring the ultraviolet avalanche photodetector to a critical state. When ultraviolet light is incident, it is absorbed by the a-Ga₂O₃ / ITO heterojunction, causing an avalanche effect. The InGaAs / InP heterojunction conducts under the reverse bias voltage, forming a photocurrent loop. When infrared light is incident, it passes through the upper wide-bandgap material and is absorbed by the lower InGaAs / InP heterojunction, generating an infrared detection current. Simultaneously, the voltage across the inGaAs / InP heterojunction changes. According to the voltage divider principle, the reverse bias voltage across the a-Ga₂O₃ / ITO heterojunction increases, triggering an avalanche phenomenon. The avalanche current increases the loop current, amplifying the infrared signal detection current and increasing the signal gain.

[0017] This invention utilizes the characteristic of avalanche photodetectors to trigger the avalanche effect under two conditions: receiving light and increasing the reverse bias voltage. During the detection process, it induces the PIN-type infrared photodetector and the solar-blind ultraviolet avalanche photodetector to mutually excite each other, effectively improving the gain of the dual-color cascaded detector.

[0018] In summary, this invention enables rapid detection of ultraviolet and infrared light from the incident detector, and the current signal is significantly amplified by the avalanche gain of the avalanche detector, thereby improving the optical detection efficiency.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) This invention makes full use of the characteristics of ITO material with high light transmittance and low resistivity, and creatively proposes ITO material as a transition layer between infrared photodetector and solar-blind ultraviolet photodetector, and at the same time as a component of the heterojunction of solar-blind ultraviolet detector and a conductor part of the current loop, thus realizing the integration of small devices of infrared detector and ultraviolet detector.

[0021] (2) The present invention fully considers the band structure of the material and arranges the wide bandgap material a-Ga2O3 on the upper layer of the device to realize the detection and absorption of ultraviolet band signals and prevent ultraviolet light from entering the lower infrared detection area; infrared light passes through the upper material to reach the lower layer and is absorbed by the narrow bandgap material, thus realizing the simultaneous response to ultraviolet and infrared signals.

[0022] (3) When the InGaAs / InP heterojunction is excited by infrared light, the present invention generates a small current and reduces the voltage across the infrared photodetector. By using the principle of voltage division in the circuit, the voltage across the ultraviolet avalanche photodetector is increased, and an avalanche effect is induced in the circuit. This method effectively improves the current gain of the infrared photodetector and increases the detector's response rate to infrared light signals.

[0023] Therefore, addressing the difficulty of achieving dual-band ultraviolet-infrared detection using existing methods, this invention enables the simultaneous detection of short-wave infrared signals and solar-blind ultraviolet signals. In this invention, the InGaAs / InP heterojunction for detecting infrared signals and the a-Ga2O3 / ITO heterojunction for detecting solar-blind ultraviolet signals can mutually excite each other under operating conditions by changing the circuit voltage divider. Therefore, compared to ordinary photodetectors, the detector prepared in this invention has a higher current gain. This detector exhibits good performance under weak illumination conditions and can be applied in fields such as military detection, target reconnaissance, and lidar. Attached Figure Description

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in detail with reference to the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the preparation process of the method of the present invention;

[0026] Figure 2 A schematic diagram of the device structure of a cascaded dual-color photodetector that amplifies optical signals based on the avalanche effect, provided for an embodiment of the present invention;

[0027] Figure reference numerals: 1-n-type InP substrate; 2-InGaAs layer; 3-p-type InP layer; 4-p-type InGaAs layer; 5-Ti / Au electrode; 6-ITO thin film; 7-a-Ga2O3 thin film; 8-Ti / Au electrode. Detailed Implementation

[0028] This embodiment provides a cascaded dual-color photodetector that amplifies optical signals based on the avalanche effect. The detector, from top to bottom, comprises: an a-Ga₂O₃ thin film, an ITO thin film, an n-InP thin film, an i-InGaAs thin film, a p-InP thin film, a p-InGaAs thin film, and a Ti / Au electrode. The Ti / Au electrode is grown on the surface of both the a-Ga₂O₃ and p-InGaAs thin films. At room temperature, the photodetector receives ultraviolet and infrared light signals. Wires are led from the Ti / Au electrode to a back-end circuit, and the photoelectric signal changes are obtained through signal processing.

[0029] To make the problem solved by the present invention, the method adopted, and the effect achieved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] A method for fabricating a cascaded dual-color photodetector based on avalanche effect for optical signal amplification is as follows: Figure 1 As shown, the details are as follows:

[0031] Step 1: Fabricate a semiconductor heterojunction for an infrared photodetector structure.

[0032] Step 1.1: Perform Zn diffusion treatment on the InP substrate to obtain an n-InP substrate;

[0033] Step 1.2: Deposit an InGaAs layer on the n-InP thin film with a material thickness of 2 μm;

[0034] Step 1.3: Deposit a p-InP layer on top of the InGaAs thin film with a material thickness of 200 nm;

[0035] Step 1.4: Deposit a p-InGaAs layer on the p-InP thin film with a material thickness of 100 nm;

[0036] Step 1.5: Perform back thinning on the n-InP layer.

[0037] Step 2: An ITO film is grown on the upper surface of the n-InP film on the infrared photodetector structure using magnetron sputtering technology.

[0038] ITO was deposited on another surface of an n-InP thin film by magnetron sputtering under an ambient temperature of 200℃ and high oxygen pressure.

[0039] Step 3: Grow an a-Ga2O3 film on the surface of an ITO film using magnetron sputtering.

[0040] A-Ga2O3 thin film was grown at low temperature by radio frequency magnetron sputtering using a 99.99% gallium oxide ceramic target as the sputtering source. A 100×100μm window was photolithographically etched on an ITO substrate. Amorphous gallium oxide was deposited by magnetron sputtering at room temperature. 99.99% high-purity argon and oxygen were introduced into the gas pipeline of the reaction chamber, with an Ar:O2 ratio of 9:1. The sputtering time was 120 min, and the thickness was 900 nm.

[0041] Step 4: Deposit Ti / Au electrodes on the surfaces of n-InP and a-Ga2O3 films using magnetron sputtering.

[0042] Ti / Au electrodes were prepared on the surfaces of n-InP and a-Ga2O3 films by DC sputtering, with an electrode size of 20×20μm.

[0043] The materials selected for the preparation of the heterojunction in this invention are InGaAs, InP, ITO, and a-Ga2O3. InGaAs and InP are second-generation semiconductor materials and are preferred materials for preparing infrared detectors. a-Ga2O3 is a third-generation semiconductor material with a band gap of 5.3 eV. It has the characteristics of a large band gap, high electron saturation drift velocity, and stable chemical properties. It has significant material performance advantages for photoelectric detectors operating in the ultraviolet band and is an ideal material for preparing ultraviolet detectors.

[0044] Reference Figure 2 , Figure 2 This is a schematic diagram of an infrared-ultraviolet cascaded dual-color photodetector provided in an embodiment of the present invention. The infrared-ultraviolet cascaded dual-color photodetector employs the above-described... Figure 1The invention is fabricated using the method shown. Specifically, this invention uses n-InP as a substrate and fabricates an infrared detector on its surface. Further, an ITO thin film is grown on the surface of the n-InP film. Utilizing the conductivity and light transmittance properties of the ITO film, a current loop is formed, transmitting infrared light and absorbing ultraviolet light. An α-Ga₂O₃ thin film is grown on the surface of the ITO film, forming a semiconductor heterojunction with the ITO film. Upon absorbing ultraviolet light, this triggers a photoelectron avalanche effect. This invention endows the photodetector with the ability to simultaneously achieve infrared and ultraviolet detection, improving both photoresponsivity and specific detectivity. The wavelengths used for photodetection in this invention are mainly ultraviolet and infrared light, with 254 nm ultraviolet light and 1550 nm infrared light as the main detection bands.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for fabricating a cascaded dual-color photodetector based on the avalanche effect to amplify optical signals, characterized in that, The fabricated cascaded dual-color photodetector is configured as follows: the photocurrent generated by the infrared photodetector structure is injected into the solar-blind ultraviolet avalanche photodetector structure via an ITO thin film; the infrared detector and the ultraviolet avalanche detector are mutually excited by bias voltage modulation, inducing an avalanche effect in the circuit, thereby cascading amplification of the infrared signal. The specific steps of the fabrication method are as follows: Step 1: Fabrication of a semiconductor heterojunction for detecting infrared light, specifically including: First, diffusion treatment of the InP substrate to obtain an n-InP substrate; second, deposition of an i-InGaAs thin film with a thickness of 2 μm on the n-InP substrate; third, deposition of a p-InP thin film with a thickness of 200 nm on the i-InGaAs thin film; fourth, deposition of a p-InGaAs thin film with a thickness of 100 nm on the p-InP thin film; fifth, back-side thinning of the n-InP substrate. Step 2: An ITO thin film is grown on the other surface of the n-InP substrate on the upper layer of the infrared photodetector structure using magnetron sputtering technology; Step 3: Grow an a-Ga2O3 film on the surface of an ITO film using magnetron sputtering. Step 4: Deposit Ti / Au electrodes on the surfaces of p-InGaAs and a-Ga2O3 films using magnetron sputtering.

2. The method for fabricating a cascaded dual-color photodetector based on the avalanche effect for optical signal amplification according to claim 1, characterized in that, In a high oxygen pressure environment, an ITO thin film is deposited on another surface of an n-InP substrate using magnetron sputtering technology.

3. The method for fabricating a cascaded dual-color photodetector based on the avalanche effect for optical signal amplification according to claim 1, characterized in that, Using a 99.99% gallium oxide ceramic target as the sputtering source, a-Ga2O3 thin films were grown at low temperature on ITO thin films using radio frequency magnetron sputtering technology.

4. The method for fabricating a cascaded dual-color photodetector based on the avalanche effect for optical signal amplification according to claim 1, characterized in that, Ti / Au electrodes were prepared on the surfaces of p-InGaAs and a-Ga2O3 films using DC magnetron sputtering.

5. A cascaded dual-color photodetector based on the avalanche effect for optical signal amplification, obtained by the preparation method according to any one of claims 1 to 4.

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