The effects of AlxGa1-xN/GaN superlattice insertion on the structural homogeneity, photoluminescence lifetime (τPL), and defect densities were studied in cubic (c-) GaN epilayers on (001) GaAs substrates grown by low-pressure metalorganic vapor phase epitaxy. Values of the full-width at half-maximum of both the (002) X-ray diffraction peak and near-band-edge excitonic photoluminescence peak were significantly decreased by the insertion of appropriate short-period AlGaN/GaN superlattices between the c-GaN epilayer and the c-GaN template layer prepared on a substrate-decomposition-shielding GaN layer deposited at a low temperatures. The density or size of Ga-vacancy (VGa)-related defects in the c-GaN epilayer was significantly reduced. Simultaneously, the value of excitonic photoluminescence lifetime at 293K was improved from approximately 20 to 230ps, indicating a tremendous reduction of the non-radiative defect density.

Reduced Defect Densities in Cubic GaN Epilayers with AlGaN/GaN Superlattice Underlayers Grown on (001) GaAs Substrates by Metalorganic Vapor Phase Epitaxy. M.Sugiyama, T.Nosaka, T.Suzuki, T.Koida, K.Nakajima, T.Aoyama, M.Sumiya, T.Chikyow, A.Uedono, S.F.Chichibu: Japanese Journal of Applied Physics, 2004, 43[3], 958-65