Microwave magnetoplasma study of lattice and electronic properties of PbTe

The $q=0$ transverse-optic-phonon frequency ωTO has been determined in PbTe from microwave magnetoplasma experiments at frequencies near 70, 138, and 335 GHz, over the temperature range 4.2≤T80 K. Both n-type and p-type bulk samples and p-type epitaxial thin films on BaF₂ substrates were studied. At the lowest temperatures, ωTO is almost temperature independent and has the value 12.3 ±{} 1.0 cm^-1. This implies, via the Lyddane-Sachs-Teller relation, a static lattice dielectric constant εₛ3000, depending on the value assumed for the high-frequency dielectric constant ε_∞. At temperatures above 30 K, ωTO shows a temperature dependence which is consistent with Curie-law behavior of the static lattice dielectric constant, εₛ∝(T-TC)^-1. Curie temperatures near both - 150 and - 80 K were found, but the favored experimental value is TC=-151±7 K. Several band-edge electronic parameters were also determined: transverse-conduction-band-edge effective mass, m1cm₀=0.0164±0.001; transverse-valence-band-edge effective mass, m₁ᵥm₀=0.021±0.001: valence-band-edge mass anisotropy ratio, K₀ᵥ=13.4±2.0. The critical importance of sample preparation and characterization procedures is discussed, together with possible reasons for the discrepancies among previously reported values of εₛ, which scatter over two orders of magnitude.