Multiphonon hopping of electrons on defect clusters in amorphous germanium

A high density of microvoids could cause inhomogeneous distribution of deep localized states in amorphous germanium. The electronic transport in such media is no longer dominated by Mott variable-range hopping. The dc conductivity is proportional to $T^n$ with n≃6, suggesting that the transport is by a multiphonon process with weak electron-lattice coupling. The ac conductivity is explained by the Scher-Lax continuous-time random-walk approximation, producing information on the hopping rate.