Raman study of interface roughness in (GaAs)n/(AlAs)n superlattices grown on tilted surfaces: Evidence of corrugation of the (113) interface

The Effect of Interface Diffusion on Raman Spectra of Wurtzite Short-Period GaN/AlN Superlattices

We present an extensive theoretical and experimental study to identify the effect on the Raman spectrum due to interface interdiffusion between GaN and AlN layers in short-period GaN/AlN superlattices (SLs). The Raman spectra for SLs with sharp interfaces and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of the random-element isodisplacement model. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, showed that the bands related to A₁(LO) confined phonons are very sensitive to the degree of interface diffusion. As a result, a correlation between the Raman spectra in the range of A₁(LO) confined phonons and the interface quality in SLs is obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy.

Coherence of elementary excitations in a disordered electron system

The localization properties of the single-particle and collective electron excitations were investigated in the intentionally disordered GaAs/AlGaAs superlattices by weak-field magnetoresistance and Raman scattering. The localization length of the individual electron was found to be considerably larger than that of the collective excitations. This suggests that the disorder has a weaker effect on the electrons than on their collective motion and that the interaction which gives rise to the collective effects increases localization.