Correlation between temperature dependence of Raman shifts and in-plane strains in an AlGaN/GaN stack

Abstract

The temperature dependence of Raman shifts for different layers and different optical phonon modes in an AlGaN/GaN stack was examined in this study. The slopes of the Raman shifts as a function of temperature for the GaN and AlxGaN layers were found to vary, especially for the E2 high mode compared with that for the A1 (LO) mode. To further investigate these fluctuations in the temperature dependence of Raman shifts, a detailed evaluation was conducted for the depth distribution of in-plane strains in the AlGaN/GaN stack by detecting each of the layers simultaneously in a single Raman spectrum. The temperature dependence fluctuations for the E2 high modes of the AlxGaN layers are considered to be related to the in-plane strain distribution with depth.