Defects and Interfacial Structure in Ge/Si Layers

During thermal oxidation of Ge – ion implanted Si, Ge is completely rejected from the growing oxide and forms an intermediate crystal layer between the Si and SiO₂. The segregated Ge rich layer is epitaxial with the Si substrate and leads to enhanced oxidation rates. The increased oxidation rates are shown to arise because the segregated Ge modifies the interfacial growth kinetics and lowers strain in the oxide layer. Kinetic and interfacial structure information are provided over a range of temperatures and oxidation ambients. Enhanced oxidation rates studied were found to be consistent with a modified reaction at the oxide/Si interface. An anomalous behaviour is exhibited for steam oxidation at 800 °C, due to the viscous flow of the intermediate Ge layer. This behaviour is characterised and the mechanisms responsible are discussed. Also a comparison using HRTEM is made between Ge/SiO₂ and Si/SiO₂ interface. This shows that the undulations at the interface are different indicating a reduced binding energy due to the presence of substitutional Ge atoms.