OPTICAL STUDIES OF GAN AND GAN ALGAN HETEROSTRUCTURES ON SIC SUBSTRATES/

We present the results of spectroscopic studies on GaN based epitaxial materials on SiC substrates by metalorganic chemical vapor deposition . A variety of techniques has been used to study the optical propertie s of GaN epilayers and GaN/AlGaN heterostructures. Sharp spectral stru ctures associated with the intrinsic free excitons were observed by ph otoluminescence and reflectance measurements from GaN based materials grown on SiC substrates. The residual strain was found to have a stron g influence in determining the energies of exciton transitions. Picose cond relaxation studies of exciton decay dynamics suggest that an AlGa N cladding layer with a small mole fraction of AIN can be relatively e ffective in enhancing the radiative recombination rate for excitons by reducing the density of dislocations and suppressing surface recombin ation velocity in the GaN active layer for the GaN/AlGaN heterostructu re samples. (C) 1996 American Institute of Physics.