PHOTOELECTRONIC ANALYSIS OF IMPERFECTIONS IN GROWN STANNIC OXIDE CRYSTALS,
OKLAHOMA STATE UNIV STILLWATER RESEARCH FOUNDATION
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A study of the imperfection properties of grown stannic oxide single crystals was made using photoelectronic techniques. The primary purpose was to propose an energy level scheme for defects in these samples based on the results of spectral response, thermally stimulated current, thermal quenching, dark conductivity as a function of temperature, and photo-thermoelectric voltage measurements. Thermally stimulated current results indicate the existence of three trapping levels with average activation energies of 0.21, 0.52 and 0.60 ev. Extrinsic thermal quenching results have established that these levels are all trapping states for electrons, implying that the two shallow ones are completely compensated while the deeper one is only partially compensated. Intrinsic thermal quenching measurements indicate the existence of a compensated acceptor level lying 0.33 ev above the valence band and acting under certain conditions as a sensitizing center. Also found are more-or-less discrete levels having optical activation energies of approximately 1.0, 1.3 and 1.8 ev.