Abstract

We have previously measured the photoconductive response in a GaAs/AlGaAs multiple quantum well (MQW) pin diode on picosecond timescales by the excite-probe technique.¹ These results give information on the fundamental operating limits of the quantum-well self electrooptic effect device (SEED) and MQW photodetectors. The rise time of the transient transmission change generally decreased as a function of reverse bias voltage with a pronounced minimum (30 ps) at a voltage level corresponding to resonant electron tunneling. A numerical algorithm has been developed to model this transient response. The electric field dependent time constants for the various carrier dynamic processes are determined first, such as escape of carriers from the wells by tunneling or thermionic emission, drift of carriers in the field, and recapture of carriers into the wells. The temporal and spatial evolution of the photoexcited electron and hole populations are then calculated self-consistently by including the space-charge contributions to the local electric field throughout the structure. The decay of the transmission change is included by allowing transverse diffusion of the excitation in the n-doped contact region. We also include the effects of a nonuniform applied field due to impurities. We obtain good agreement with experiment and are thus able to understand the nature of the cross-well transport.

© 1991 Optical Society of America