Influence of Grain Size and Room-Temperature Sputtering Condition on Optical and Electrical Properties of Undoped and Ga-Doped ZnO Thin Films

다국어 초록 (Multilingual Abstract)

The optical and the electrical properties of undoped zinc-oxide (ZnO) thin lms of various thicknesseswerecomparedwiththoseofGa-doped(GZO)thinlms. Transparent,high-qualityundoped ZnO and GZO lms were deposited successfully using radio-frequency (RF) sputtering at room temperature. The lms were polycrystalline with a hexagonal structure and a strongly preferred orientation along the c-axis. The lms had an average optical transmission >85 % in the visible partoftheelectromagneticspectrum. TheundopedZnOthinlmsweremoretransparentthanthe GZO thin lms. The ZnO thin-lm transistors (TFTs) were operated in the enhancement mode withathresholdvoltageof2.5V.Incontrary,theGa-dopedZnOTFTswereoperatedinadepletion mode with a threshold voltage of {3.4 V. We successfully demonstrated undoped and the Ga-doped ZnO TFTs by using conventional SiO2 gate insulators at room temperature. We postulate that undoped ZnO lms, which have not been treated to improve the optical properties, can be used, instead of doped ZnO lms, in transparent devices for next generation optoelectronic devices.

다국어 초록 (Multilingual Abstract)

The optical and the electrical properties of undoped zinc-oxide (ZnO) thin films of various thicknesses were compared with those of Ga-doped (GZO) thin films. Transparent, high-quality undoped ZnO and GZO films were deposited successfully using radio-frequency (RF) sputtering at room temperature. The films were polycrystalline with a hexagonal structure and a strongly preferred orientation along the $c$-axis. The films had an average optical transmission $>$85 \% in the visible part of the electromagnetic spectrum. The undoped ZnO thin films were more transparent than the GZO thin films. The ZnO thin-film transistors (TFTs) were operated in the enhancement mode with a threshold voltage of 2.5 V. In contrary, the Ga-doped ZnO TFTs were operated in a depletion mode with a threshold voltage of --3.4 V. We successfully demonstrated undoped and the Ga-doped ZnO TFTs by using conventional SiO$_2$ gate insulators at room temperature. We postulate that undoped ZnO films, which have not been treated to improve the optical properties, can be used, instead of doped ZnO films, in transparent devices for next generation optoelectronic devices.

참고문헌 (Reference)

1 C. Y. Kagan, "Thin Film Transistors" Dekker,New York 2003