Valence-band changes in ${\mathrm{Sb}}_{2\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$${\mathrm{Te}}_3$ and ${\mathrm{Sb}}_2$${\mathrm{Te}}_{3\mathrm{-}\mathit{y}}$${\mathrm{Se}}_{\mathit{y}}$ by transport and Shubnikov–de Haas effect measurements

Measurements of galvanomagnetic effects in the temperature range 4.2–300 K and photoinduced ‘‘transient thermoelectric effect’’ (TTE) along the ${\mathit{C}}_2$ axis at 300 K have been made for two types of solid solutions of semiconductors ${\mathrm{Sb}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Te}}_3$ (0≤x≤0.4) and ${\mathrm{Sb}}_2$ ${\mathrm{Te}}_{3\mathrm{-}\mathit{y}}$ ${\mathrm{Se}}_{\mathit{y}}$ (0≤y≤1.8). By incorporating In atoms into the ${\mathrm{Sb}}_2$ ${\mathrm{Te}}_3$ lattices, Hall coefficients, Hall mobilities, and the frequencies of Shubnikov–de Haas (SdH) oscillations are varied systematically. For ${\mathrm{Sb}}_2$ ${\mathrm{Te}}_{3\mathrm{-}\mathit{y}}$ ${\mathrm{Se}}_{\mathit{y}}$, the Hall mobility is decreased with y up to y=0.7 and then increased appreciably in the range 0.7<y0.6 in ${\mathrm{Sb}}_2$ ${\mathrm{Te}}_{3\mathrm{-}\mathit{y}}$ ${\mathrm{Se}}_{\mathit{y}}$, confirming the existence of a valence band, whose anisotropy in the effective mass along the ${\mathit{C}}_2$ direction is evaluated to be of the order of 2–2.5. Based on these experimental data we have proposed the most probable band model for these solid solutions.