Hopping conductance in electron irradiated n-type GaAs

A.c. conductivity is studied in n-type electron irradiated GaAs at helium temperatures. For T < 25 K variable range hopping [σ is proportional to exp (- b/Tsup(1/4))] is observed. The experimentally observed low values of b(Ksup(1/4)) are discussed. At T > 30 K the conductivity exhibits an activation energy of 0.5 meV which is attributed to excitation into an upper band. The frequency dependence of hopping conductance is σ is proportional to ωsup(s) with s = 1.8 and s = 0.9 depending on the degree of radiation induced damage. (author)