Nonpolar m- and a-plane GaN thin films grown on γ-LiAlO2 substrates

Pure single-phase m- and a-plane GaN layers were fabricated on (1 0 0)- and (3 0 2)-planes of γ-LiAlO2 (LAO) substrate via metelorganic vapor deposition, respectively. Raman spectra measurement indicates that the crystallinity gradually improves with increasing layer thickness, and smaller stress exists in an a-GaN film. (3 0 2)-Plane LAO appears suitable for fabricating high-quality a-GaN layers because the layer on it shows a smoother surface with the root mean square of 60 nm, higher transmittance (85%) and narrower full-width at half-maximum value (FWHM) of X-ray rocking curve (1123 arcsec) than m-GaN on (1 0 0)-plane LAO (1735 arcsec).