Electric-Susceptibility Mass of Free Holes in SnTe

The electric-susceptibility mass mₛ of free carriers was determined at 300, 80, and 10 ^∘{}K for p-type SnTe having carrier concentrations ranging from 3.6 ×{} 10¹⁹ to 1.2 ×{} 10²¹ cm^-3. The values were determined from an analysis of the normal reflectivity of the material in the infrared region. The observed carrier concentration and temperature dependences of mₛ were used to test valence-band models recently proposed for SnTe by (i) Koehler, (ii) Rogers, and (iii) Tsu, Howard, and Esaki. In addition, a simple Cohen-type model was evaluated. It is demonstrated that none of these models provides a completely satisfactory description of our experimental results. The temperature dependence of mₛ is shown to be anomalous with regard to its relationship to the temperature dependence of the forbidden energy gap. On the basis of our results, it is concluded that the valence-band structure of SnTe is considerably more complex than indicated by the models we have considered.