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

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 E-2 high mode compared with that for the A(1) (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. Published by AIP Publishing.