Morphology and Low Temperature Electrical Transport in Heteroepitaxial Indium Nitride Films

Abstract

ABSTRACTThe correlation of low temperature electrical transport with the evolution of heteroepitaxy and morphology for sputtered indium nitride thin films has been studied. A series of indium nitride films were deposited at temperatures ranging from 50 -650 °C by reactive rf magnetron sputtering onto the (00.1) face of sapphire. Above 350 °C, a transition occurs from a continuous morphology, in which grains are in intimate electrical contact, to an open, porous morphology with poor electrical contact. This transition in morphology deeply affects the electrical transport of the semiconductor. At low deposition temperature, the electrical transport is dominated by the relatively weak intergrain scattering leading to films with moderate mobility. As the deposition temperature is raised, the increasingly porous nature of the film leads to a deterioration in electrical mobility. It is proposed here that the relevant physics of these films is analogous to that for granular solids with a distribution of electrical connectivities that suggests a scattering potential dominated by disorder. In fact, the temperature dependence of the resistivity is found to be analogous to that observed in disordered and amorphous materials. In particular, the resistivity is characterized by: 1) A very weak temperature dependence; 2) The observation of a resistance minimum; and, 3) A steep rise in the low temperature (<4K) resistivity that follows a T1/ dependence.