Carrier-type reversal in Pb-modified chalcogenide glasses

Abstract

Carrier-type reversal $(p$ to $n)$ has been observed, in ${\mathrm{Pb}}_x{\mathrm{Ge}}_{42-x}{\mathrm{Se}}_{48}{\mathrm{Te}}_{10}$ glasses $(0\mathrm{}<~x<~20)$ at 8 at. % of lead. dc electrical resistivity (ρ) and activation energy for electrical conduction $\left(\Delta E\right)$ are found to exhibit notable change at the $p-n$ transition threshold, which are associated with the change in the electron concentration during $p-n$ transition. The observed $p-n$ transition has been explained in light of the recent Kolobov model on the basis of modification of charged defect states by the introduction of lead. Also, the influence of other factors, such as band structure, polarizability of the dopant, etc., on the carrier-type reversal, has been discussed.