Accession Number : ADA011996

Title :   Electronic Excitation Processes in Semiconductors.

Descriptive Note : Final rept. 1 Jun 71-31 May 74,


Personal Author(s) : Segall,Benjamin ; Hostria,Emmanuel dela

Report Date : MAY 1975

Pagination or Media Count : 35

Abstract : The purpose of this work is to determine the mechanisms responsible for the 'fast' component of the 'induced' absroption observed by Goto and Langer in CdS crystals subjected to high intensity optical excitation. From qualitative features of the reported absorption spectra it is concluded that the relevant process (or processes) intimately involves excitons. These absorption processes are described (approximately) by a two-step mechanism in which the first step consists of the simultaneous annihilation of the photon and the creation of a virtual state in an exciton band. In the second step, the exciton is scattered into its final state. Three scattering agents are considered, namely, longitudinal optical phonons, electrons and holes, and excitons. For the purpose of interpreting the empirical data on the exciton spectra in wurtzite semiconductors, the appropriate effective Hamiltonian for the excitons is set up. Relations between the valence band parameters for a wurtzite crystal and the corresponding zinc blende crystal are established.

Descriptors :   *Semiconductors, *Excitons, Optical properties, Absorption(Physical), Band theory of solids, Laser beams, Phonons, Cadmium sulfides, Zinc sulfides, Hamiltonian, Valence, Phonons, Electrons, Holes(Electron deficiencies)

Subject Categories : Optics
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE