Ultrafast carrier dynamics at a metal-semiconductor interface

The ultrafast carrier dynamics in the high electric field at an Au-GaAs interface has been studied experimentally as well as theoretically. The photoluminescence decay time is related directly to the carrier sweepout from the GaAs depletion region, i.e., to the time needed for photoexcited electrons and holes to leave this region. This decay time has been found to increase drastically with laser input power, ranging from a few picoseconds at low excitation to values of 10-20 ps at high excitation. These results indicate a significant retardation of the sweepout, which cannot be explained by intervalley scattering and space-charge effects. From our Monte Carlo calculations it has been found that the applied electric field collapses totally almost instantaneously after laser excitation due to the enormous excess of photoexcited charges. The sweepout only recovers after some time needed to recharge the device. (C) 1996 American Institute of Physics.