Structure of the energy spectrum of holes in IV–VI materials from a different viewpoint

A twofold decrease in the hole concentration for all PbTe$\langle \mathrm{NaTe}\rangle$ samples at 77–450 K and the same effect attained at 77 K and upon heavy doping due only to the introduction of a small tin addition into PbTe, supplemented by the observation of temperature hysteresis in the hole concentration in the mentioned range, serve as the basis for the development of another approach to studying the energy spectrum in IV–VI materials alternative to the two-band model. It is based on a phenomenon common for these materials, i.e., the compensation of current carriers as a response to electrically active doping. The appearance of compensation is associated with the initial (at a temperature below 77 K) doubly-charged process of the participation of an electron pair in a single doping act of PbTe due to their mutual attraction. The situation changes with increasing temperature and with the introduction of an impurity, and studying all aspects of the transformation is the task of further research.