Accession Number : ADP006715

Title :   Hot Carrier Enhancement of Dember Photorefractive Space-Charge Fields in Zinc -blende Semiconductors,

Corporate Author : IOWA UNIV IOWA CITY

Personal Author(s) : Schroeder, W. Andreas ; Stark, Thomas S. ; Smirl, Arthur L.

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : We use a novel, nondegenerate, polarization-sensitive, transient-grating technique' to monitor the picosecond dynamics of the photorefractive effect in undoped cadmium telluride and indium phosphide:iron at 960 nm. The technique circumvents the limited temporal resolution of the two-beam coupling geometry by using a time-delayed third probe pulse (with a duration of <5 psec) to read the gratings written in the semiconductor. The technique also exploits the crystal symmetry of zincblende semiconductors by using an optically induced anisotropy in the crystal index of refraction to separate the photorefractive gratings from the stronger, coexisting instantaneous bound-electronic and free-carrier gratings. In both semiconductors, the photorefractive effect is associated with the Dember field between mobile electron-hole pairs, in contrast to the more conventional photorefractive spacecharge field connected with the separation of a mobile carriers species from a stationary, but oppositely charged, mid-gap state. In the undoped CdTe sample, which possesses no optically-active mid-gap levels, the electron-hole pairs are produced by two-photon absorption of 1.3 eV photons across the 1.44 eV band-gap of the semiconductor. The resultant -1 eV excess carrier energy, which allows hot carrier transport to dominate the initial formation of the space-charge field, causes up to an order of magnitude enhancement in the photorefractive effect on picosecond time-scales.

Descriptors :   *SEMICONDUCTORS, *DIFFRACTION, ABSORPTION, ANISOTROPY, AUGMENTATION, CONTRAST, COUPLINGS, CRYSTALS, DYNAMICS, ELECTRONICS, ELECTRONS, ENERGY, GEOMETRY, INDEXES, MOBILE, MONITORS, PHOTONS, POLARIZATION, PROBES, REFRACTION, RESOLUTION, SEPARATION, SPACE CHARGE, STATIONARY, SYMMETRY, TIME, TRANSIENTS, TRANSPORT, TWO PHOTON ABSORPTION, CADMIUM TELLURIDES, REFRACTION, INDIUM PHOSPHIDES, IRON, GRATINGS(SPECTRA), SYMPOSIA.

Subject Categories : Electricity and Magnetism
      Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE