Accession Number : ADP006752

Title :   Conduction Band and Trap Limited Mobilities in Bi sub 12 Sio sub 20,

Corporate Author : UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES

Personal Author(s) : Nouchi, P. ; Partanen, J. P. ; Hellwarth, R. W.

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : The mobility of photoexcited charge carriers in photorefractive insulators can be measured with a holographic time-of-flight technique. By illuminating the crystal with two interfering 30 ps laser pulses at the wavelength of 532 nm, we create an instantaneous sinusoidal pattern of photoexcited charge carriers. A strong electric field E sub 0 is applied across the crystal causing the sinusoidal pattern of charge carriers to drift with a velocity muE sub 0 where mu is the mobility. With a proper choice of the interference fringe spacing alpha, the superposition of this drifting charge pattern on the complementary pattern of photo-ionized traps creates an observable oscillating space charge field. We probe this oscillation by diffracting a weak cw helium-neon beam from the refractive index grating that is created via the electro-optic effect. The period Pt of the observed oscillation is the time required for photoexcited charge carriers to drift over one spatial period A. A time-flight mobility mu can therefore be simply determined using the equation.

Descriptors :   *CHARGE CARRIERS, *PHOTOCONDUCTIVITY, CRYSTALS, DRIFT, ELECTRIC FIELDS, INTERFERENCE, LASERS, MOBILITY, OSCILLATION, PROBES, PULSES, REFRACTIVE INDEX, SPACE CHARGE, TRAPS, VELOCITY, HOLOGRAPHY, REFRACTION, GRATINGS(SPECTRA), ELECTROOPTICS, PHOTOELECTRONS, ILLUMINATION, SYMPOSIA.

Subject Categories : Optics
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE