Light Scattering from Single — Particle Electron and Hole Excitations in Semiconductors

Abstract

Light scattering from single-particle electron excitations has been observed in GaAs, InP, CdTe, and AlSb, as well as from holes in p-type GaAs and n-type epitaxial GaAs.

A YAG: Nd³⁺ laser operating at 1.06 microns with a CW output of up to 2. W was used to excite the single-particle excitations. GaAs samples with electron concentrations from 4 × 1¹⁴ to 3 × 1¹⁸ cm^-3 were measured. The single-particle scattering could be observed in samples with electron concentrations as low as 10¹²cm^-3. For electron concentrations of a few times 10¹⁶ cm^-3 and less, the single-particle excitation spectrum overlaps and Landau damps the collective plasmon excitations at room temperature. The intensity of the single-particle scattering in single-crystal GaAs was measured as a function of polarization and concentration to determine the dominant scattering mechanisms. In p-type GaAs at room temperature the scattering from both light and and heavy holes was observed, the line shape being characterized by two superimposed Maxwellian velocity distributions having different thermal velocity cutoffs. The effect of an applied electric field on the velocity distribution of electrons is discussed.

Operated with support from the U. S. Air Force.