A Modified Model Dielectric Function for Analyzing Optical Spectra of InGaN Nanofilms on Sapphire Substrates

Abstract

Due to a lower InN bandgap (Formula presented.), (Formula presented.) epifilms are considered valuable in the development of low-dimensional heterostructure-based photonic devices. Adjusting the composition x and thickness d in epitaxially grown films has offered many possibilities of light emission across a wide spectral range, from ultraviolet through visible into near-infrared regions. Optical properties have played important roles in making semiconductor materials useful in electro-optic applications. Despite the efforts to grow (Formula presented.) /Sapphire samples, no x- and d-dependent optical studies exist for ultrathin films. Many researchers have used computationally intensive methods to study the electronic band structures (Formula presented.) and subsequently derive optical properties. By including inter-band transitions at critical points from (Formula presented.), we have developed a semiempirical approach to comprehend the optical characteristics of InN, GaN and (Formula presented.). Refractive indices of (Formula presented.) and sapphire substrate are meticulously integrated into a transfer matrix method to simulate d- and x-dependent reflectivity (Formula presented.) and transmission (Formula presented.) spectra of nanostructured (Formula presented.) epifilms. Analyses of (Formula presented.) and (Formula presented.) have offered accurate x-dependent shifts of energy gaps for (Formula presented.) (x = 0.5, 0.7) in excellent agreement with the experimental data.