Metastable effects in the DC conductivity of hydrogenated amorphous germanium

Abstract

The authors report on the effect of thermal equilibration on the dark conductivity of undoped optimized a-Ge:H with an optical gap of 1.03 eV. The freeze-in temperature T_E is about 160 degrees C. The isothermal relaxation of the conductivity follows a stretched exponential function. The inverse equilibration time tau ^-1 is thermally activated with an energy E_tau of 1.4-1.5 eV. It is then shown that, as compared with the values for a-Si:H T_E, tau and E_tau are only slightly different. The results are fully consistent with the model of dispersive diffusion of hydrogen.