Structural and optical investigation of GaN grown by metal-organic chemical vapor deposition

Structural and optical properties of GaN grown on (0001)-oriented sapphire substrates by low pressure metal-organic chemical vapor deposition were investigated by XRD, ellipsometry, PL and other optical methods. The thickness of the GaN sample was about 1.5 mum. Seen by XRD, the existence of the strong (0002) diffraction peak with a very narrow FWHM value of 0.1 and the high order GaN (0004) diffraction peak confirms a good quality of the GaN films grown on sapphire substrate by using a multi-step growth procedure. Optical transparency of the GaN samples induces strong interference oscillations below E-0 (3.44eV) in the measured dielectric function spectra and reflective spectra. In low temperature PL spectra, the red shift of the peak and decreased intensity of PL are visible. The former can be attributed to the involvement of band tail states, and the latter can be accounted for by the decreasing non-radiative recombination lifetime.