RAMAN LINE-SHAPE ANALYSIS OF RANDOM AND SPONTANEOUSLY ORDERED GAINP2 ALLOY

We have measured the temperature dependence of the Raman frequency and linewidth of the GaP-like LO phonon of random and spontaneously order ed GaInP2 alloys. The width of the asymmetric Raman band is strongly i nfluenced by disorder and the anharmonicity of the lattice. The half-w idth towards the high-energy side of the Raman band of the GaP-like ph onon is independent of temperature, while the half-width on the low-en ergy side does depend on temperature. Though no obvious differences ar e observed in the temperature dependence of the Raman spectra of the r andom and the ordered alloys, the GaP-like Raman band of the ordered s amples narrows for incident photon energies near the fundamental gap o f the alloy. We attribute the narrowing of the Raman band to the inhom ogeneities in the material caused by the existence of a statistical di stribution of partially ordered domains with different order parameter s eta. From the observed width of the dispersion of the Raman linewidt h as a function of incident photon energies under resonance conditions , it is concluded that samples grown at higher temperatures possess a narrower distribution of domains.