Large Area In InGaAs-MSM Photodetector And The Analysis Of The Dark Current

MSM(Mental- Semiconductor-Mental) photodetector has low capacitance for its symmetric and simple structure of the back-to-back Schottky diodes. Its compatiblity with FETs(Field Effect Transistors), together with the planarity of the contacts makes it easy to be integrated. Compared with PIN and APD structure, MSM structure has great advantages for fabricating photodetectors with large area and high bandwidth. As direct gap semiconductor, InGaAs has high quantum efficiency and electron mobility and it has wide wavelengths. All these advantages make InGaAs-MSM detectors more and more widely used in the field of communication.In this paper, the basic situation and the significance of InGaAs-MSM photodetector have been present. Then the working process of the detectors has been talked based on the properties of InGaAs and the theory of MSM structure. The main parameters and the measures for improving the performance have been proposed. Based on the above, the InGaAs-MSM photodetector has been designed as follows. The lattice matched InP is used as the substrate. 1000 nm InGaAs is designed as the astive layer and buffer layers are designed on both sides of the active layer. The InAlGaAs/InGaAs short period superlattices, the InAlAs Schottky barrier enhancement and the SiO2 passivation are fabricated to reduce the dark current. The area of the detector is 100×100 μm2 and the interdigitated electrode finger width and the sapce are both 3 μm.The 100×100 μm2 InGaAs-MSM photodetector has been successfully fabricated and the photoelectric parameters have been characterizated as follows: the peak response wavelength is 1670 nm and the relative response at 1550 nm is 0.8804, the dark current density is reduced to 0.6-0.8 pA/ μm2(at 5 V bias), the 3dB bandwidth is 6.8 GHz, the rise time is 70 ps, the responsibility can be 0.554 A/W at 1550 nm and the external quantum efficiency of the absorption region is 88.7%. Inhibition mechanisms of the InAlGaAs/InGaAs short period superlattices, the InAlAs Schottky barrier enhancement and the SiO2 passivation have been analyzed.