PHOTOREFRACTIVE P-I-N-DIODE QUANTUM-WELL SPATIAL LIGHT MODULATORS

We demonstrate the performance of all-semiconductor photorefractive p-i-n diodes operating in the longitudinal quantum-confined Stark geometry. Low-temperature-grown shallow quantum wells provide high-mobility vertical transport, and potential steps incorporated into the semiconductor buffer layers increase the transit time across the buffer and therefore increase the quantum efficiency for trapping of charge before it is swept out to the doped p-type and n-type contacts. The buffer design and the doped contacts both make all-semiconductor photorefractive devices possible, with peak transient output diffraction efficiencies approaching 3%, but without the need for dielectric insulating layers. We also redefine device speed by making a distinction between transient rise times and frequency response, showing that in these p-i-n devices the update rate is an order of magnitude slower than the inverse rise time. (C) 1995 American Institute of Physics.