Photoreflectance study of Si-doped GaN grown by metal-organic chemical vapor deposition

Si-doped n-GaN films grown by metal-organic chemical vapor deposition were studied by photoreflectance (PR) spectroscopy. Based on the intense optical transitions observed in the room-temperature PR spectra, the energy positions of the near-band-edge transition fur n-GaN samples with different Si-doping levels were determined through theoretical curve fitting under the weak-field approximation. Furthermore, based on the observed dependence of the redshift in the near-band-edge transition energy with the carrier concentration and the approach using the many-body theory, the band-gap renormalization coefficient for GaN was derived to be (2.4 +/- 0.5) x 10(-8) eV cm. This value was found to be nearly 35% larger than that for GaAs. (C) 1998 American Institute of Physics.