A kind of inas avalanche photodiode and its manufacturing method

Abstract

The invention relates to an avalanche photodiode and a method for manufacturing the same, in particular to an InAs avalanche photodiode. The photodiode is of an absorbed charge multiplication and separation structure, and multiplication layers are of super-lattice structures. The invention further relates to a method for manufacturing the InAs avalanche photodiode. The method mainly includes steps of S1, generating the multiplication layers of the super-lattice structures with multiple quantum wells; S2, generating charge layers, gradient layers and optical window layers; and S3, forming PN junctions by an Zn diffusion process or a Cd diffusion process. The InAs avalanche photodiode and the method have the advantages that dark current, particularly tunneling dark current, is mainly reduced by the super-lattice structures of the multiplication layers for the narrow-gap attribute of InAs materials; and wide-gap materials matched with the InAs materials are adopted, various structures of the photodiode are further optimized, and accordingly effects of low noise, high gain, high speed and high response are realized.

Description

Technical field [0001] The invention belongs to the technical field of photodiodes, and particularly relates to an InAs avalanche photodiode and a manufacturing method thereof. Background technique [0002] At present, due to the rapid development of optical communication systems, the requirements for the responsiveness and speed of the receiver are getting higher and higher. Compared with PIN detectors, avalanche photodiodes (APDs) have higher sensitivity due to their internal gains and are widely used in optical communication systems. However, the randomness of gain will be accompanied by additional noise; and for traditional APDs such as InAlAs, InP, Si, InGaAs and other materials, there is a limitation of gain-bandwidth product, that is, when the gain is high, the avalanche settling time increases , The bandwidth will be reduced, thus limiting the rate of the receiver. Therefore, the APD with low noise, high response, low dark current, and high gain band-wide product can be...

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Problems solved by technology

At present, there are some mainstream methods to reduce the dark current of InAs, such as: 1) low-temperature working method, which enables the APD to work in the range of 290K-77K in a refrigerated environment. Compared with 290K, the dark current at 77K can be reduced by 6 orders of magnitude, but The gain is also reduced from 17 to 8, which reduces the maximum gain-bandwidth product, limits the available gain, and works under cooling, requiring an additional cooling device, which is inconvenient for application in communication systems; 2) Improve the manufacturing process and add a diffusion barrier layer This method reduces the surface dark current and the bulk diffusion current respectively. When the growth temperature of InAs is 470°C, the lattice defects are small. The two-step etching method is adopted. First, the H 3 PO 4 :H 2 o 2 :H 2 O solution followed by 1:8:80 H 2 SO 4 :H 2 o 2 :H 2 O solution, which can reduce the dark current by an order of magnitude, using AlAs 0.16 Sb 0.84 The wide bandgap acts as a minority carrier blocking layer to prevent minority carriers in the p-type contact layer from diffusing to the intrinsic multiplication region, and can also reduce the dark current by an order of magnitude, but the dark current is still high; 3) He ion-implanted planar structure, using ion The method of implantation made InAs APD with flat plate structure to eliminate the surface dark current and increase the resistance of InAs, because the diode is not completely isolated, resulting in a large dark current; 4) Zn diffusion process on semi-insulating substrate, using Zn diffusion method to minimize Surface dark current, using a semi-insulating GaAs substrate, reduces parasitic capacitance, and is easy to integrate with other devices. Zn diffusion can reduce surface dark current, but due to lattice mismatch and defect density, the dark current is still very large; 5) Improve the electric field and Reduce the intrinsic doping concentration method, increase the concentration of the p-type contact layer, thereby increasing the barrier height, reducing the minority carrier diffusion current from the p-type contact layer, and neutralizing the intrinsic Unintentional n-type doping improves the uniformity of the electric field, increases the width of the depletion region, increases the maximum gain, and improves the process to reduce the intrinsic doping concentration, thereby reducing the bulk dark current, and the dark current is reduced by nearly an order of magnitude

The above methods are all improvements for the bulk diffusion dark current and surface leakage current of InAs APD, and the maximum gain is still limited by the tunneling dark current

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