Characterization of MBE-grown Ga1-xAlxAs alloy films by Raman scattering

Molecular beam epitaxy (MBE)-grown ternary Ga1-xAlxAs films, with Al compos ition x ranging from 0 to 1 in steps of 0.1, have been studied by Raman sca ttering at room temperature and at 80 K, The observed broadening and asymme try of the first-order longitudinal-optical phonon spectra induced by alloy disorder are simulated using the spatial correlation model, The obtained c orrelation length for GaAs-like and AlAs-like modes are observed to decreas e as the reduction of Ga composition 1-x and Al composition x, respectively . It is also shown that the correlation length depends sensitively on the c omposition. No significant temperature or phonon mode dependence is found. A combination with thermodynamic analysis suggests that the random composit ional distribution in alloy seems to be the dominant contribution to this d isorder effect. Copyright (C) 1999 John Wiley & Sons, Ltd.