Trap level spectroscopy of undoped and Ga-doped Bi12GeO20 using thermally stimulated conductivity

Abstract

The analysis of thermally stimulated conductivity (TSC) measurements performed on ‘‘pure’’ Bi12GeO20 (BGO) and BGO doped with gallium is presented. The TSC data show many overlapping TSC peaks in the temperature range of interest (80–300 K) which arise from a complex array of trapping states. The TSC signals from both pure BGO and Ga-doped BGO are similar, consisting of a series of large peaks below 160 K and many smaller overlapping peaks between 180 and 300 K. The analysis shows that the large peaks below 160 K in undoped BGO arise from two trapping centers, each characterized by a distribution of activation energies centered at ∼0.24 and ∼0.29 eV, with distribution widths of ∼0.065 eV. In the Ga-doped BGO sample the large peak seen below 180 K arises from a single trapping center at ∼0.29 eV with a distribution width of ∼0.085 eV. Activation energies, frequency factors, and concentrations of trapping states have been determined.