Thermal stress effects on local electronic properties on N-type GaN crystals in contact with Au/Ti/Cr electrode film by micro-Raman spectroscopy at high temperatures

Abstract

Raman spectra of the E2H mode and the LOPC mode in n-type GaN crystals in contact with a Au/Ti/Cr film electrode are measured from room temperature to 200 °C by micro-Raman spectroscopy. Thermal stress in the measured area on the interface between GaN and the film electrode is analyzed by Raman spectroscopy, and the obtained values are well reproduced by the finite element method (FEM). Those values increase with temperature, and both thermal stress and thermal expansion broaden the linewidth due to crystal distortion. We calculate the electron density values near the interface in n-type GaN by spectral analysis for the LOPC mode. The electron density tends to decrease significantly with increasing temperature. The resistivity values near the interface tend to increase significantly with increasing temperature in comparison with those far from the interface.