The effects of cap layers on electrical properties of indium nitride films

The unintentional n-type doping in the indium nitride thin films was investigated. The electron density decreases from 3.5 x 10(19) to 9 x 10(18) cm(-3) and the mobility increases from 4 to 457 cm(2) V(-1) s(-1) when the thickness increases from 50 to 350 nm. This can be explained by assuming the film consists of a surface accumulation layer and a bulk layer. It was found that the accumulation layer can be eliminated by capping the surface with silicon nitride, GaN or zinc nitride of 2 nm each, respectively; while an AlN cap layer will cause the formation of two-dimensional electron gas at the AlN/InN interface. (C) 2010 American Institute of Physics. [doi:10.1063/1.3475400]