Optical constants and dispersion energy parameters of heterostructured Ga₂O₃/GaN films

The demand for heterojunction materials is on the increase due to the great achievements of modern nanotechnology that has stimulated the enormous research interest for investigating their material properties. Heterostructured Ga2O3/GaN have been widely deployed for electronic and optoelectronic applications, but its several optical parameters have rarely been exploited. The present work attempts to report some of the optical parameters of Ga2O3/GaN films prepared at different temperatures by the chemical vapour deposition method. Morphological characterization revealed increased film thickness with increased temperature. Structural analysis revealed the coexistence of beta-Ga2O3 and GaN phases. The change in temperature induced crystallite size growth, reduction in dislocation density and stacking faults. UV-vis measurements showed two distinct bandgaps belonging to the beta-Ga2O3 and GaN crystal phases, with a systematic broadening 4.61-4.79 eV for beta-Ga2O3 and 3.41-3.45 eV for GaN as the temperature was increased. The absorption and extinction coefficients were in the orders of 10(3) and 10(-1), respectively. The refractive index ranged between 1.55 and 1.86, while the static refractive index ranged between 1.45 and 1.98. The porosity of the films decreased with increased temperature and film thickness. Also discussed in detail were the dielectric constants, the optical dispersion energy using Wemple-DiDomenico model, oscillator strength, oscillator energy, and the non-linear optical susceptibility of the films.