Temporal and spectral characteristics of back-illuminated InGaAs metal-semiconductor-metal photodetectors

We report dramatic differences in the impulse response and wavelength dependence of back versus top illuminated In/sub 0.53/Ga/sub 0.47/As planar metal-semiconductor-metal devices. Via direct measurement of transit-time limited devices we identify the mechanisms involved and thereby allow the optimum design of multi-Gbit, high responsivity back-illuminated devices. We show that responsivities greater than 0.8 A/W are achievable with >8 GHz bandwidth for 50-μm-diameter devices.