QUANTUM INTERFERENCE CONTROL OF ELECTRICAL CURRENTS IN GAAS

In an earlier publication, preliminary observations of the generation of electrical currents were reported in GaAs and low-temperature-grown GaAs (LT-GaAs) at 295 K using quantum interference control of single- and two-photon band-band absorption of 1.55- and 0.775-mu m ultrashort optical pulses. Time-integrated currents were measured via charge col lection in a metal-semiconductor-metal (MSM) electrode structure, Here we present detailed characteristics of this novel effect in terms of a simple circuit model for the MSM device and show how the injected cu rrent depends on MSM parameters as well as optical coherence, power, a nd polarization. For picosecond pulse excitation with peak irradiance of only 30 MW/cm(-2) (1.55 mu m) and 9 kW/cm(-2) (0.775 mu m), peak cu rrent densities of similar to 10 A/cm(-2) at peak carrier densities of 10(15) cm(-3) are inferred from the steady-state signals. This compar es with 50 A/cm(-2) predicted theoretically; the discrepancy mainly re flects inefficient charge collection at the MSM electrodes.