Optical properties of nearly stacking-fault-free m-plane GaN homoepitaxial films grown by metal organic vapor phase epitaxy on low defect density freestanding GaN substrates

Abstract

Prospective optical properties were demonstrated for nearly stacking fault-free m-plane GaN homoepitaxial films grown by metal organic vapor phase epitaxy on the m-plane freestanding GaN substrates. Values of full width at half maximum of x-ray rocking curves were close to the substrate values being 31arcsec for the (101¯0) diffraction with ⟨0001⟩ azimuth and 48arcsec for the (101¯2) diffraction. Threading dislocation densities were lower than 5×106cm−2. The film surfaces exhibited atomically flat morphology with well-aligned monolayer steps. Low-temperature photoluminescence (PL) spectra exhibited polarization-dependent well-resolved bound and free exciton emission lines, and a characteristic π(k⊥c,E∥c)-polarized PL line was also observed. Room-temperature effective PL lifetime of the free exciton peak increased with increasing supply ratio of ammonia to trimethylgallium, and a record long value for m-plane GaN (268ps) was obtained.