Photoconductive Sampling Circuits Using Low-Temperature GaAs Interdigitated Switches

Characterisation of electronic devices at frequencies up to several hundred GHz can be achieved using electrooptic1 or photoconductive sampling. GaAs grown at low temperature by molecular beam epitaxy (LT GaAs) is a suitable material for fabrication of switches for photoconductive sampling due to its ultrafast carrier lifetime (~ 1 ps or less)2, high breakdown voltage, and low on-state resistivity. High-responsivity LT GaAs photodetectors have been demonstrated using submicron interdigitated structures3.