Study of exciton localized by random potential in indirect gallium arsenide phosphide alloys
Lai, Shui Tong
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https://hdl.handle.net/2142/25530
Description
Title
Study of exciton localized by random potential in indirect gallium arsenide phosphide alloys
Author(s)
Lai, Shui Tong
Issue Date
1980
Doctoral Committee Chair(s)
Klein, Miles V.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
exciton
random potential
indirect gallium arsenide phosphide alloys
photoluminescence
Language
en
Abstract
We have studied in detail a new structure Mx/0 in photoluminescence spectra from n-type indirect GaAs P alloys. The intensity of Mx/0 starts
l -x x
to saturate relative to that of the donor-bound exciton (Do) at very low excitation laser po\vcr. It has a low activation energy (2 meV) and prominant X-point phonon sidebands. Its wave function is effective-mass-like
and is associated with the X-point in K-space. We interpret the MO band as due to excitons localized by the random potentials in the alloys. Lifetime measurements show that the Mx/0 excitons are relatively long lived (tens of microseconds) and it varies over the spectral regions of the M~ emission band. This can be understood in terms of the energy-dependence of the effective range of the excitons in the presence of impurity centers in the sample. Such characteristic is unique for the Anderson-type localized excitons. The valley-anisotropy (V-A) splitting of the localized exciton is directly observed under resonant excitation at Mx/0. The lineshape of the enhancement curves of a prolllinent longitudinal accoustic phonon (LAX) side-
band of Mx/0 changes with temperature. This provides information which is necessary for the identification of the V-A split excited state. The pseudo-extended nature of the excited state plays an important role in the low activation energy of Mx/0. The asymmetric lineshape of Mx/0 is qualitatively explained.
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