Si- and Ge-Doped GaN Films Grown with GaN Buffer Layers

Si- and Ge-doped GaN films were grown with GaN buffer layers. Si-doped GaN films, of which the carrier concentration was as high as 2×10 19 /cm 3 , were obtained. Every Si-doped GaN film showed a surface morphology that was smooth and mirrorlike. Ge-doped GaN films, of which the carrier concentration was as high as 1×10 19 /cm 3 , were obtained. Surface morphology of Ge-doped GaN films became poor around this carrier concentration. Both dopings showed good linearity of the carrier concentration as a function of the flow rate of GeH 4 and SiH 4 . Therefore, Ge and Si are suitable n-type dopants for GaN.