The optical properties ofn-type GaN are investigated for Si doping concentrations ranging from5×1016to7×1018 cm−3.The photoluminescence linewidth of the near-band gap optical transition increases from 47 to 78 meV as the doping concentration is increased. The broadening is modeled in terms of potential fluctuations caused by the random distribution of donor impurities. Good agreement is found between experimental and theoretical results. The intensity of the near-band-gap transition increases monotonically as the doping concentration is increased indicating that nonradiative transitions dominate at a low doping density. The comparison of absorption, luminescence, reflectance, and photoreflectance measurements reveals the absence of a Stokes shift at room temperature demonstrating the intrinsic nature of the near-band edge transition. ©1997 American Institute of Physics.