Shallow optically active structural defect in wurtzite GaN epilayers grown on stepped 4H-SiC substrates

Abstract

A number of wurtzite GaN epilayers directly grown on 4H-SiC-(0001) misoriented by 0, 3.5°, 5°, 8°, and 21° with plasma-assisted molecular-beam epitaxy were optically characterized with photoluminescence and excitation spectra. An intense shallow-defect emission peak locating at energy position ~70 meV lower than the near band edge emission peak at 3.47 eV is found in the emission spectra of the GaN films on 4H-SiC misoriented by 8° and 21°. Stacking mismatch boundaries are supposed to be the candidate causing the optical transition. Combined with the low-temperature photoluminescence excitation spectra of the films, the location of the electronic level induced by the structural defect is determined to be about 100 meV above the valence-band maximum of GaN. Show more