Influence of Si doping on the infrared reflectance characteristics of GaN grown on sapphire

Si-doped GaN films grown on sapphire are investigated by infrared reflectan ce. A damping behavior of the interference fringes is observed, and interpr eted to be due to the presence of an interface layer between the film and t he substrate. A theoretical calculation using a two-layer model to take int o account the interface layer resulted in this damping in agreement with th e experiment. The damping behavior and an improvement of interface properti es by Si incorporation are demonstrated. (C) 1999 American Institute of Phy sics. [S0003-6951(99)00644-0].