Study of optical characteristics of cubic GaN grown on GaAs (001) by MOCVD

We report the optical characterization of the cubic GaN film grown on GaAs (001) by MOCVD. The FWHMs of the PL spectra show that the c-GaN samples have different crystal quality. Raman spectra are used to study the optical phonon modes in the c-GaN epitaxy layer. TO and LO phonon peaks are found at 552 cm^-1 and 739 cm^-1, respectively. Besides these emissions, we also observe the TO_B and LO_B phonons attributed to the boundary layer in sample C. The E₂ phonon from hexagonal phase can be used to identify the hexagonal phase. Annealed at higher temperature, the boundary layer effect decreases while the quantity of hexagonal phase increases in sample C.