CARRIER TRANSPORT IN A PHOTOREFRACTIVE MULTIPLE-QUANTUM-WELL DEVICE

Using picosecond time-resolved four-wave mixing we have investigated t he turn-on and turn-off mechanisms in a photorefractive multiple quant um well spatial light modulator with Stark geometry. We show that hole s contribute to the turn-on time as a slower rise (similar to 300 ps) of the diffraction efficiency, Furthermore, the diffraction grating is dominated by either electrons or holes, depending on the applied volt age polarity relative to the diffraction of illumination. The grating decays in 0.4-8.5 ns, depending on the grating spacing. We show that t he decay is due to lateral transport of carriers at the multiple quant um well/dielectric interfaces, where low-temperature grown layers can increase the diffraction efficiency and device resolution. (C) 1996 Am erican Institute of Physics.