dc Conductivity Mechanisms in Amorphous Group-IV Semiconductors

Dc conductivity measurements have been performed at low temperature in amorphous ${\mathrm{Si}}_x{\mathrm{Sn}}_{1-x}$ semiconductor alloys. It is shown that the experimental results are correctly explained by the variable-range-hopping theory, whereas the present form of the small-polaron model is unable to account for the low-temperature experimental results. The values of the physical parameters extracted from the variable-range-hopping theory are physically reasonable and give some information about the electronic energy levels within the semiconductor band gap.