Pressure dependence of the electronic band gap in 6H-SiC

Abstract

Photoluminescence experiments on 6H-SiC doped with nitrogen have been performed at low temperature (T = (29 ± 2) K) under hydrostatic pressure up to 5 GPa. The pressure coefficients of the S0, R0, P0, S02, and R02 emission lines related to the neutral nitrogen donor bound excitons were determined. The pressure coefficient of the indirect gap of 6H-Sic deduced from the P0 line turns out to be +2.0 meV/GPa. Nonrelativistic band structure calculations within the density-functional theory based on the local density approximation are used to calculate the pressure coefficients of the indirect band gaps of the 6H, 4H, and 3C SiC polytypes. The comparison with available experimental data shows good agreement with the theoretical results.