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 reflectance. A damping behavior of the interference fringes is observed, and interpreted to be due to the presence of an interface layer between the film and the substrate. A theoretical calculation using a two-layer model to take into account the interface layer resulted in this damping in agreement with the experiment. The damping behavior and an improvement of interface properties by Si incorporation are demonstrated. (C) 1999 American Institute of Physics. [S0003-6951(99)00644-0].