The electrical conductivity, Seebeck coefficient, and Hall coefficient of micron thick films of amorphous ${\mathrm{Sb}}_2{\mathrm{Te}}_3$ have been measured as functions of temperature from room temperature down to as low as $200\mathrm{K}$. The electrical conductivity manifests an Arrhenius behavior with a pre-exponential factor that is larger than that of a conventional semiconductor. The Seebeck coefficient is $p$ type. Unlike a conventional semiconductor, the energy characterizing the Seebeck coefficient’s temperature dependence, about $0.10\mathrm{eV}$, is considerably smaller than the activation energy of the electrical conductivity, about $0.28\mathrm{eV}$. In addition, the heat-of-transport constant of the Seebeck coefficient is much larger than that of conventional semiconductors. The Hall mobility is low (near $0.1{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ at room temperature), anomalously signed ($n$-type), and increases with rising temperature with an activation energy of about $0.05\mathrm{eV}$. These results are consistent with the charge carriers being holelike small polarons that move by thermally assisted hopping.

• Received 7 November 2005

DOI:https://doi.org/10.1103/PhysRevB.73.165211