Shallow trapping centers in Bi12GeO20 single crystals by thermally stimulated current measurements

Abstract

Bi 12 GeO 20 single crystals were investigated by thermally stimulated current (TSC) experiments performed in the temperature range of 10-290 K. Recorded TSC glow curve exhibited six distinctive peaks with maxima at around 90, 105, 166, 209, 246, 275 K. The analyses of the obtained glow curve were accomplished by curve fitting and initial rise methods. The analysis results were in good agreement that the TSC peaks appeared in the glow curve due to existence of trapping levels with activation energies of 0.10, 0.18, 0.23, 0.53, 0.68 and 0.73 eV. These trapping levels were estimated to be hole traps above valence band. The heating rate dependent TSC glow curves were also obtained for various rates between 0.30 and 0.45 K/s. The changes of TSC intensity, peak maximum temperature and full-widths-half-maximum values with heating rates were studied in detail. TSC intensity decreased and peak maximum temperature increased with increasing heating rate. Determination of defects and trapping/stimulation mechanism of those are significant for technological applications since local states in these materials take critical role for device performance.