Investigation of Spontaneous Ordering in GaInP using reflectance
difference spectroscopy
J.S. Luo, J.M. Olson, K.A. Bertness
National Renewable Energy Laboratory, Golden, Colorado 80401
M.E. Raikh and E.V. Tsiper
Department of Physics, University of Utah, Salt Lake City, Utah 84112
Reflectance difference spectroscopy (RDS) is applied to the study of
optical anisotropy in spontaneously ordered GaInP grown by
metalorganic chemical-vapor deposition. The degree of ordering in
GaInP has been associated previously with a shift of the band-gap
energy &Delta E0, and a crystal-field valence-band splitting
A(C). Theoretically and experimentally, both quantities are
approximately proportional to the square of the order parameter, which
varies from 0 to 1 for disordered and perfectly ordered GaInP,
respectively. In this study, we examined a number of GaInP layers
grown under conditions that yield a wide range of band-gap
energies. The main spectral feature in all samples is a bulk-related,
asymmetric peak at E0 with a long tail that extends well below E0 and
a sharp, high-energy cutoff at E0 + &Delta(C). The intensity of this
peak is proportional to \sqrt{&Delta E0} and is therefore linear
with the order parameter. By annealing GaInP in PH3/H-2 mixtures, we
find that the RD spectral features for energies between E0 + &Delta(C)
and 3 eV are mainly surface induced. Evidence for a bulk-related RDS
peak at E1 is also found.
J. Vac. Sci. Technol. B12, 2552 (1994)
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