Study on excitonic absorptions in wurztite GaN by photovoltaic spectra at room temperature

Abstract

Clear exciton absorption peak has been observed at room temperature by photovoltaic spectra, on a GaN layer grown on (000l)-plane Sapphire by metalorganic chemical vapor deposition. From the spectra, we obtained the wurztite GaN room temperature A and B exciton transition energies, and the energy gap to be 3.401eV, 3.408eV and 3.426eV, respectively. We have also performed photovoltaic measurements with varied light incidence angles, and observed the polarization behavior of exciton absorption in GaN. In conjuction with previous room temperature photoreflectance measurements, this work provide direct and reliable assessment of GaN semiconductor crystal layers.