FREQUENCY-DOMAIN DEMONSTRATION OF TRANSIT-TIME-LIMITED, LARGE-AREA INGAP-INP-INGAAS MSM PHOTODETECTORS

We report transit-time-limited bandwidth (12 GHz at 12-V bias) for an InGaP-InP-InGaAs MSM photodetector with 2-mu m finger spacing, (100-mu m)(2) active area, and abrupt heterojunctions, The same device exhibi ts a very gradual rolloff up to 20 GHz, with an on/off isolation of gr eater than 40 dB across the measurement band, This is one of the first reports of transit-time-limited performance measured in the frequency domain for InGaAs-based MSM photodetectors, and these are the largest such devices reported to date, A pseudomorphic In0.8Ga0.2P cap layer is found to have an electrically stable free surface, requiring no spe cial pre-treatment or passivation.