Effects of heterogeneity and prestress field on phonon properties of semiconductor nanofilms

Abstract

The phonon dispersion relation, phonon group velocity and phonon density of state in GaN-based wurtzite nanofilms under prestress fields are investigated theoretically. Considering the acoustoelastic effects and spatial confinement effects, the acoustic phonons properties in stressed AlN/GaN/AlN nanofilms are derived by using the elasticity model, comparing with those in the pure AlN nanofilm and pure GaN nanofilm. Numerical simulations demonstrate that the heterogeneity in GaN-based nanofilms can modify the phonon dispersion relations of nanofilms, leading to the change of phonon group velocity and phonon density of state. The stress field can significantly affect the phonon properties of GaN-based heterostructural nanofilms, e.g. the positive stress decreases the phonon energy and group velocity while enhances the density of state. The influence of the stress field is also sensitive to the thickness of each component in heterostructural nanofilms. The present work will be useful in tuning the phonon properties through phonon engineering and strain/stress engineering to control the thermal and electrical performance in GaN-heterostructure-based electronic devices.