High-performance large-area InGaAs MSM photodetectors with a pseudomorphic InGaP cap layer

We report the fabrication and characteristics of high-performance InGaAs MSM photodetectors with a 300-μm×300-μm square and a 300-μm-diameter circular detection area. With a pseudomorphic In/sub 0.9/Ga/sub 0.1/P cap layer, the detectors exhibit dark current densities less than 1 pA/μ on finger spacing. Bandwidth over 1 GHz has been obtained for these large-area detectors. Our results also show that the circular detector exhibits better speed performance as compared to the square one due to its smaller parasitic RC constant.