Thickness Dependence of Hopping Transport in a-Ge Films,

The conductivity of gas free thin films of a-germanium was measured as a function of temperature and of film thickness. Existing theories of hopping conduction have been modified to apply to the very thin films. The results obtained are very consistent with the experimental data, indicating strongly that hopping conduction near the Fermi energy is the conduction mechanism responsible for the conductivity below room temperature. The comparison between the experimental results and the theoretical predictions permits separate evaluation of the radius a of the localized wave functions at the Fermi energy, and the density of states at the Fermi energy. Author