Optical properties of GaN epilayers on sapphire

The optical properties of GaN epilayers grown by metal-organic vapor-phase epitaxy on (0001)-oriented sapphire are investigated by means of photoluminescence, reflectance, and differential spectroscopy. We obtain quantitative information about the intrinsic or extrinsic nature of the 2 and 300 K photoluminescence features. From detailed investigations of the reflectance properties of these layers we can quantify the residual strain field in these layers and determine the GaN deformation potentials. Comparison of these values with quantities measured on other semiconductors with wurtzite symmetry is also addressed. Last we utilize photoreflectance spectroscopy to measure exciton binding energies. (C) 1996 American Institute of Physics.