Optical Properties of AlGaN/GaN HEMT Structures

This study investigated the optical properties of AlGaN/GaN/sapphire high-electron-mobility transistor (HEMT) structures. The AlGaN/GaN/sapphire HEMT structures were grown by metal-organic chemical vapour deposition (MOCVD). The aim of this study was to determine the optical properties, layer thicknesses, and band gap energies of the buffer layers. The Swanepoel envelope method was employed to calculate the refractive index, layer thickness, absorption coefficient, and extinction coefficient. These parameters were obtained for the transparent region as well as the weak- and medium-absorption regions. The Tauc method, together with the Kubelka–Munk method, was used to determine the optical band gap energy of the AlGaN layer.