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 $\text{σ∝exp(-b/T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)]}$ is observed. The experimentally observed low values of $\text{b(K}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)}$ 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 ∝ ω^S with S=1.8 and S=0.9 depending on the degree of radiation induced damage.