A number of wurtzite epilayers, grown directly onto 4H-SiC (00▪1) misoriented by 0, 3.5, 5, 8 or 21°, using plasma-assisted molecular-beam epitaxy were optically characterized on the basis of photoluminescence and excitation spectra. An intense shallow-defect emission peak, located about 0.070eV lower than the near-bandedge emission peak at 3.47eV, was found in the emission spectra of the GaN films on 4H-SiC which was misoriented by 8° or 21°. Stacking mismatch boundaries were supposed to have caused the optical transition. When combined with the low-temperature photoluminescence excitation spectra of the films, the location of the electronic level introduced by the structural defect was deduced to be about 0.10eV above the valence-band maximum of GaN.

Shallow Optically Active Structural Defect in Wurtzite GaN Epilayers Grown on Stepped 4H-SiC Substrates. S.J.Xu, H.J.Wang, S.H.Cheung, Q.Li, X.Q.Dai, M.H.Xie, S.Y.Tong: Applied Physics Letters, 2003, 83[17], 3477-9