Abstract
We report on high-pressure optical absorption measurements on InN epilayers with a range of free-electron concentrations (5×1017-1.6×1019 cm -3) to investigate the effect of free carriers on the pressure coefficient of the optical band gap of wurtzite InN. With increasing carrier concentration, we observe a decrease of the absolute value of the optical band gap pressure coefficient of wurtzite InN. An analysis of our data based on the k¿p model allows us to obtain a pressure coefficient of 32 meV/GPa for the fundamental band gap of intrinsic wurtzite InN. Optical absorption measurements on a 5.7-¿m-thick InN epilayer at pressures above the wurtzite-to-rocksalt transition have allowed us to obtain an accurate determination of the indirect band gap energy of rocksalt InN as a function of pressure. Around the phase transition (~15 GPa), a band gap value of 0.7 eV and a pressure coefficient of ~23 meV/GPa are obtained. © 2012 American Physical Society.
