Epitaxy and Structural, Electrical, and Optical Characterization of Pb1-xSnxTe Semiconductor Layers Grown by MBE on CdTe/GaAs Hybrid Substrates

Abstract

Pb_1-xSn_xTe is a IV–VI substitutional semiconductor alloy exhibiting excellent thermoelectric and mid-infrared optoelectronic properties controlled by the tin content. In recent years, this material has gained additional interest due to discovery of a topological crystalline insulator state for large values of x. High-quality Pb_1-xSn_xTe crystals can be grown both as bulk materials and thin layers. However, due to its high thermal expansion and lattice mismatch with commercial semiconductor substrates such as Si or GaAs, the choice of substrates for epitaxial growth of Pb_1-xSn_xTe layers is very limited, and thermally matched cleaved BaF₂ (111) substrates have typically been used. In this article, we report the growth of Pb_1-xSn_xTe (x = 0–1) layers by molecular beam epitaxy using original hybrid substrates made of a  few  micrometer  thick  CdTe  layer  grown on commercial 2 in GaAs (001) wafers. The basic structural, electrical, and optical characteristics of the grown structures are presented, demonstrating the high crystalline quality of the Pb_1-xSn_xTe layers with a rock-salt structure, with a lattice parameter exhibiting Vegard law in the entire composition range, p-type electrical conductivity with hole concentration varying by three orders of magnitude from PbTe to SnTe, and a mid-infrared optical spectrum dominated by plasma reflectivity and interference effects.