Photoreflectance study of band-gap renormalization in Si-doped GaN

Abstract

Si-doped n-GaN films grown by metal-organic chemical vapor deposition (MOCVD) have been studied by photoreflectance (PR) spectroscopy. Based on the intense and plentiful optical transitions observed in room temperature PR spectra and the fitting with theoretical calculation under weak-field approximation, the energy positions of the near band-edge transition for n-GaN samples with different Si-doping levels were determined. Furthermore, according to the observed remarkable red shift in the near band-edge transition energy with increasing the carrier concentration and by the approach of the many-body theory, the band-gap renormalization coefficient for GaN is derived to be (2.4 ± 0.5) × 10 -8 eV cm. This value is found to be nearly 35% larger than that for GaAs and can be used to interpret the measurement results reported by other research groups satisfactorily. © 1998 Elsevier Science B.V. All rights reserved.