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-μm finger spacing, (100-μm)
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active area, and abrupt heterojunctions. The same device exhibits a very gradual rolloff up to 20 GHz, with an on/off isolation of greater 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 In/sub 0.8/Ga/sub 0.2/P cap layer is found to have an electrically stable free surface, requiring no special pre-treatment or passivation.