Differential tunneling conductance in multicomponent solid solutions Bi$_{2-x}$Sb$_{x}$Te$_{3-y-z}$Se$_{y}$S$_{z}$

Differential tunnel conductance of the interlayer van der Waals surface (0001) was investigated in $n$-Bi$_{2-x}$Sb$_{x}$Te$_{3-y-z}$Se$_{y}$S$_{z}$ multicomponent solid solutions at $x$ = 0.2, $y=z$ = 0.09, optimized for near room temperatures with a high power factor, and at $x$ = 0.4, $y$ = 0, $z$ = 0.06 with optimal thermoelectric properties for low temperatures and a high Seebek coefficient. It is shown that the intensity of the fluctuations of the Dirac point energy $\Delta E_{\mathrm{D}}$, a shift the top of the valence band and presence of surface levels in the energy gap formed by impurity defects is determined with composition and thermoelectric properties of solid solutions. The contribution of the surface states of Dirac fermions increases in $n$-Bi$_{1.8}$Sb$_{0.2}$Te$_{2.82}$Se$_{0.09}$S$_{0.09}$ solid solution with a high power factor due to significant decrease of the surface concentration near the charge neutrality point and the growth of fermion mobility.