LOCALIZATION AND DIFFUSION OF ENERGY VIA CONFINED PHONON MODES IN SEMICONDUCTOR SUPERLATTICES

We study the effects of disorder on energy transport by confined optic al-phonon modes in semiconductor superlattices. We investigate, in par ticular, whether it is possible to obtain Anderson localization of con fined phonon modes by interface and barrier alloy disorder in superlat tices like the GaAs/AlxGa1-xAs system. We develop a formalism for desc ribing the transport of kinetic energy through the system and apply a diagrammatic perturbation theory that allows inclusion of disorder sca ttering. A simple model of the confined phonons shows that the strengt h of the disorder scattering is far too weak for localization to occur in realistic samples. We find, however, that a crossover from ballist ic transport of energy by phonons to diffusive transport is expected a s a function of increasing well width and alloy concentration. Possibl e implications for recent experiments are discussed.