LINEAR-OPTICAL AND NONLINEAR-OPTICAL PROPERTIES OF GAN THIN-FILMS

Results of a linear- and nonlinear-optical investigation of GaN thin f ilms epitaxially deposited onto (0001)oriented sapphire are reported. Wavelength- and angle-dependent linear transmission measurements were used to determine the thickness and the refractive index in the 500-12 00-nm spectral region for a series of six GaN films. Analysis of angle -dependent, second-harmonic (SH) transmission profiles at 532 nm provi ded a quantitative evaluation of chi(xzx)(2), chi(zxx)(2), chi(zzz)(2) and a determination of the GaN lattice structure and tilt angle betwe en the optical axis of the film and the surface normal of the sample. Dispersion effects between 500 nm and 1.064 mum prevented efficient SH production in individual GaN films that were greater than 2.5 mum in thickness. However, field calculations on a proposed multilayer GaN-sa pphire structure observed a ninefold increase in the transmitted SH po wer as compared with a single GaN film.