THE ABSENCE OF P-N TRANSITION IN BI-MODIFIED NON-CRYSTALLINE THIN FILMS OF GE20TE80-XBIX IS DEMONSTRATED BY THE ELECTRONIC CONDUCTIVITY.

Abstract

Well-characterized Bi-modified amorphous thin films of Ge 20 Te 80-x Bi x (x=0, 0-19, 2-93, and 7-35) prepared by flash evaporation are reported for their Ac conductivity and dielectric relaxation. These films show no p-n transitions in the frequency range of 500 Hz-10 kHz and the temperature range of 180 K-450 K. It is discovered that the ac conductivity, sigma ac (omega), is proportional to omega^3. The correlated-barrier hopping method is used to analyze the temperature dependences of sigma ac (omega) and the exponent s. It is discovered that in all compositions, electrical conduction occurs through bipolaron/single polaron hopping processes at low and high temperatures. The production of Bi-induced defects that participate in single polaron hopping occurs at a lower Bi concentration (x = 0.19).The density of such flaws does not alter significantly with further increases in the Bi concentration (x = 2 * 93 and 7-35). The addition of Bi atoms to the alloy has no discernible effect on the density of defect states participating in bipolaron conduction. This characteristic of the Bi impurity is comparable to how adding a Bi impurity affects the optical energy gap, de conductivity, and thermoelectric power.