Hopping Conduction in Amorphous Ge Films Condensed at 8 K

Abstract

We have studied the temperature dependence (in the temperature range of 6–80 K) of electrical conductivity of amorphous Ge films condensed at 8K but subsequently thermally heated to 30K and 80K. The results are described by Mott's type of hopping conduction within the localized states centered at the Fermi level. Below 18K the conduction is due to phonon assisted tunneling between distant hopping sites (ie $\log \text{\hspace{0.17em}σ\hspace{0.17em}∝\hspace{0.17em}1/}{\mathrm{T}}^{\text{1/4}}$ ). At higher temperatures the data is consistent with conduction due to phonon assisted hopping between nearest hopping site. Quantitive comparison with the theory leads to very reasonable values of the density of states (∼ 10²⁰ eV⁻¹ cm⁻³) and other parameters for these two processes.