Premium
Investigation of the disorder of Ga 1– x Al x As mixed crystals. Part I: Small concentrations
Author(s) -
Berdekas D.
Publication year - 2016
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201552646
Subject(s) - raman spectroscopy , polarizability , phonon , valence (chemistry) , crystal (programming language) , ion , raman scattering , chemistry , resonance (particle physics) , bond length , crystallography , spectral line , molecular physics , crystal structure , analytical chemistry (journal) , condensed matter physics , atomic physics , physics , optics , molecule , organic chemistry , chromatography , computer science , programming language , astronomy
We present calculations of the Raman intensities scattered by the phonons of the mixed crystals Ga 1– x Al x As for five small concentrations up to x = 0.14, away from resonance conditions. Each mixed crystal is approached by a primitive cell, the volume of which is 64 times the volume of the bulk zincblende primitive cell. The phonons have been calculated using a version of a three‐dimensional Valence Overlap Shell Model (VOSM) and the Raman spectra with the bond‐polarizability model (BPM). The values of the bond‐polarizability (BP) parameters of Ga–As and Al–As bonds necessary for the calculation of the Raman intensities are, for the first time, not estimated arbitrarily, but we have evaluated them using certain relations involving directly measurable quantities. We also show that the frequencies of the AlAs LO(Γ)‐like modes and their Raman profiles and intensities as well, depend, for a given Al concentration, strongly on the way the cations are distributed over the mixed‐crystal cation planes. Concerning the GaAs LO(Γ)‐like modes, differences in the cation distribution affect only a little their frequencies and their intensities, but may result in pronounced left asymmetries of the profiles of the corresponding strong Raman peaks. The comparison between the calculated and the experimental Raman spectrum for the Ga 0.86 Al 0.14 As is very encouraging, especially when the mixed crystal is described by a disorder configuration where the Al ions are gathered to neighboring cation planes.