Transport properties of (formula presented) alloy thin films grown on (formula presented)

We have grown (Formula presented) alloy thin films on (Formula presented) over a wide range of Sb concentrations (Formula presented) using molecular-beam epitaxy. Temperature-dependent electrical resistivity (ρ) and thermoelectric power (S) were studied. We have observed several differences over the bulk system. The 3.5 and 5.1% Sb alloys show semiconducting behavior, and the Sb concentration with maximum band gap shifted to a lower Sb concentration from 15% in bulk to 9%. Based on a simple interpretation of the temperature-dependent resistivity the maximum gap would be 40 meV, which is larger than that observed in bulk alloys. In addition, we have observed that the power factor (Formula presented) peaks at a significantly higher temperature (250 K) than previously reported for the bulk alloy (80 K). Differences between thin film grown on CdTe(111) and bulk alloy may arise from the effects of strain, which is supported by theoretical electronic band calculations. These results show that BiSb films may be useful as band-engineered materials in thermoelectric devices.