Weak-field magnetoresistance of indium-doped PbTe between 4.2 and 300 K

Rotational weak-field magnetoresistance (WFMR) measurements were performed between 4.2 and 300 K on thin films of (111)-oriented n-type PbTe deposited on BaF2 and doped with approximately 0.1 and 0.25 at. % In. Due to substrate-induced strain, the 0.1% In-doped sample showed a significant departure from cubic symmetry at 4.2 K corresponding to a transfer of carriers into the valley along the strain axis in the PbTe multivalley conduction band. This in-plane stretching of the film was found to persist even up to 300 K. The 0.25% In-doped film was strained to a lesser extent at 4.2 K and by room temperature had changed from a tensile strain to a compressive strain. Such a change is attributed to the opposing effects of film-substrate lattice mismatch and the difference in their thermal expansion coefficients. The WFMR for the in-plane configuration of both films displayed an unusual skewness below 300 K which is normally not allowed in (111)-oriented films, whether cubic or trigonally distorted.