CARRIER-TYPE REVERSAL IN PB-MODIFIED CHALCOGENIDE GLASSES

Carrier-type reversal (p to n) has been observed, in PbxGe42-xSe48Te10 glasses (0 less than or equal to x less than or equal to 20) at 8 at. % of lead. de electrical resistivity (rho) and activation energy for electrical conduction (Delta E) 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 tr ansition has been explained in light of the recent Kolobov model on th e basis of modification of charged defect states by the introduction o f lead. Also, the influence of other factors, such as band structure, polarizability of the dopant, etc., on the carrier-type reversal, has been discussed.