Optical Phonons inGa1−xAlxAsMixed Crystals: A Modified Random-Element Isodisplacement-Model Calculation

Abstract

The modified random-element isodisplacement model correctly predicts that ${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ forms a "two-mode"-type mixed crystal. The model calculations agree very well with a recent infrared measurement of concentration dependence of long-wavelength longitudinal and transverse optic mode frequencies of the mixed-crystal system.