Electrical properties of PbTe doped with BaF2

Abstract

We study here the p-type doping of PbTe with BaF2. For the investigation, PbTe layers were grown on (111) BaF2 substrates by molecular beam epitaxy. The beam flux ratio between BaF2 and PbTe, defined as the nominal doping level, was varied from 0.02% to 1%. The hole density increases from 5×1017 to 1×1019 cm−3 as the doping level rises from 0.02% to 0.4% and saturates at p∼1019 cm−3 for higher levels. The saturation effect was attributed to self-compensation. The carrier concentration of all samples remained almost constant as the temperature was varied from 10 to 350 K, indicating that no thermal activation is present in the whole doping range. It suggests that the impurity level in PbTe doped with BaF2 remains resonant with the valence band, similar to the native defects behavior. The low-temperature mobility showed a pronounced reduction from 50 000 to 2 000 cm2/V s as the doping level rises from 0.02% to 1%, mainly due to the substantial increase in the hole concentration. For temperatures higher than 80 K, the mobility was essentially limited by phonon scattering. Our results demonstrate that a controlled p-type doping of PbTe with BaF2 can be obtained up to 1019 cm−3.