Characterization And Electronic Structure Analysis Of Oxide Semiconductor

Transparent amorphous oxide semiconductor （AOS） materials based on doped ZnO asthe active layer of TFT are potential for AMOLED due to their advantage on the TFT propert-yes. While the electronic structure calculation of the materials based on the first principle met-hod could show the characteristics and properties all around in theory, and provide direct gui-dance for our experimental work.Thus our work focuses on the preparation and characterization of InTaZnO TFT and theelectronic structure analysis of In、Ta doped ZnO.（1） InTaZnO thin films were fabricated by rf reactive magnetron sputtering at roomtemperature, and focused on the characterization of photoelectric properties that influenced byannealing and preparation atmosphere. As a result, the mobilty of the thin films increase from0.3cm2V^-1s^-1for unannealed to15cm2V^-1s^-1for350℃annealed, but decreased to10cm2V^-1s^-1as a result of the mix of5sccm oxygen. Annealing and preparation atmosphere have no effecton the optical transmittance of the films that no less than80%.（2） InTaZnO-TFT were prepared, the properties relevant to active layer depositioncondition and bias stress stability were investigated. The device with optimized fabricationshowed the electron mobility as high as10.9cm2V^-1s^-1, the S.S. of0.15V/dec, an on/offcurrent ratio as high as108. The result showed that positive bias stress test produces a parallelshift of Vthto the positive direction and little change in S.S., the negative bias stress test has noeffect on the performances.（3） Systematically calculated the electronic structures of ZnO and then ZnO with intrin-sic point defects (Z_ni、O_i、V_Zn、V_O). ZnO was a direct band gap semiconductor material witha direct gap0.8711eV. O_i、V_Znare acceptor defects and Z_ni、V_Oare donor defects.（4） In、Ta doped ZnO were calculated, In、Ta respectively produced a donor level below thebottom of conduction band,and the Fermi level move into the conduction band, but high dopantconcentration produce deep donor level that caused absorption at visible wavelengths.