The selection of gas chemistry in reactive ion etching of AlGaN/GaN heterostructures

In this study, we discuss a scope of different gas mixtures intended for reactive ion etching of Al_xGa_1-xN/GaN heterostructures in relation to percentage composition of aluminum. The results of etching process are strongly dependent on the process parameters and gas mixture applied. The selected mixture of BCl₃/Cl₂/Ar provides a good stability of plasma and quality of etched heterostructure mesas. The test structures of AlGaN/GaN for the RIE process were grown on a c-plane sapphire in a vertical flow LP-MOVPE (low pressure Metalorganic Vapour Phase Epitaxy) system. The surface morphology and topography of mesa structures were studied using atomic force microscope working in tapping mode and scanning electron microscope. The results of etching process for intended process parameters as well as the correlation between the gas mixture, parameters and obtained mesa structures are discussed in this article.