The optical properties of n-type GaN are investigated for Si doping co
ncentrations ranging from 5 x 10(16) to 7 x 10(18) cm(-3). The photolu
minescence linewidth of the near-band gap optical transition increases
from 47 to 78 meV as the doping concentration is increased. The broad
ening is modeled in terms of potential fluctuations caused by the rand
om distribution of donor impurities. Good agreement is found between e
xperimental and theoretical results. The intensity of the near-band-ga
p transition increases monotonically as the doping concentration is in
creased indicating that nonradiative transitions dominate at a low dop
ing density. The comparison of absorption, luminescence, reflectance,
and photoreflectance measurements reveals the absence of a Stokes shif
t at room temperature demonstrating the intrinsic nature of the near-b
and edge transition. (C) 1997 American Institute of Physics.