Electrical and galvanomagnetic properties of nanocrystalline gallium nitride films

Nanocrystalline GaN films were deposited on quartz substrates at ∼25 Pa with deposition temperature within 210-270 K using high pressure magnetron sputtering technique. Electrical, galvanomagnetic and microstructural properties were measured at different temperatures for these films. Studies on the variation of conductivity with temperature indicated Efros and Shklovskii (E-S) hopping within the Coulomb gap to be the predominant carrier transport process in the lower temperature region in these nanocrystalline GaN films. A cross-over from Mott's hopping in higher temperature region to E-S hopping in the “soft” Coulomb gap was noticed with lowering of temperature. Hall mobility was found to be dominated by the combined effects of scattering from ionized impurities, acoustic phonon and non-polar optical phonons.