Epitaxial PbSe and Pb1−xSnxSe: Growth and electrical properties

Abstract

Epitaxial layers of PbSe and Pb1−xSnxSe have been grown on cleaved BaF2 and SrF2 single-crystal substrates by vacuum deposition of the evaporated binary compounds. The influence of the effusion conditions on the stoichiometry of the molecular beam is considered and it is shown that evaporation of PbSe results in two-phase layers that contain precipitated lead. Coevaporation of selenium compensated the excess lead and permitted the control of n- or p-type carrier concentrations in epitaxial layers in the range 3×1016−6×1017 cm−3. Structural studies indicate that the layers are single crystals with about the same concentration of low-angle grain boundaries as observed on the substrates. Low-temperature Hall mobilities were measured that are as large as those obtained with annealed bulk crystals. The value 4.8×105 cm2/V sec for a PbSe layer with 9.2×1016 hole cm−3 is the largest mobility measured for this material. Below 77°K the mobilities depend markedly on carrier concentration and thermal history of the specimens.