AC conductivity measurements in electron-irradiated germanium

Abstract

AC conductivity is studied in crystalline germanium irradiated by 1.5 MeV electrons at liquid helium temperatures. A sufficient degree of damage occurs to allow the observation of nearest-neighbour hopping conductance. In n-type germanium the formation of complex defects by annealing of the samples at 60 and 110K leads to a hopping conductance obeying Mott's law ( sigma infinity exp-b/T14/). Two different values of b are observed in the temperature region 4-70K, the lower one being attributed to electron-electron interaction (variable-number hopping) and the higher one to variable-range hopping.