Electric-field-dependent photoresponse of multiple quantum well modulator

By monitoring the quantum-confined Stark effect using subpicosecond laser pulses, it is shown that the intrinsic photoconductive rise time of a multiple quantum well (MQW) pin modulator is highly field-dependent. Photoconduction times across about 1 micron of intrinsic GaAs/AlGaAs material range from the relatively slow at low fields to extremely fast at higher fields. The technique used here is of wide applicability for measurement of intrinsic speeds in MQW devices, and should be extendable to time-resolved measurement of resonant tunneling phenomena in samples of only a few quantum wells, possibly using waveguide geometry.