Surface charge transport in PbSxSe1−x and Pb1−ySnySe epitaxial films

We have measured the Hall coefficient and Hall mobility at 77 and 300 K of n‐ and p‐type PbSxSe1−x and Pb1−ySnySe epitaxial films on (111) BaF2 as a function of thickness. Transport measurements were made after exposure to air and after vacuum annealing and overcoating with either 50 A of indium or 3000 A of As2S3. The variation of the Hall coefficient and Hall mobility as functions of thickness showed evidence of a highly p‐type surface layer on all samples exposed to air. The p‐type layer is attributed to surface states produced by adsorbed oxygen. We have used the Petritz two‐layer model to fit the dependence of the 77 K Hall coefficient and Hall mobility on sample thickness. This analysis indicates the surface mobilities of the alloys are 5–10X lower than the bulk mobilities. This implies diffuse scattering at the air‐exposed surface but may also be due to diffuse scattering from the semiconductor–substrate interface, or both. We have observed large size effects in n‐type Pb1−ySnySe films resulting fr...