Doped ZnO의 전기적 및 광학적 특성

Abstract

ZnO films co-doped with H and Al(HAZO) were prepared by sputtering ZnO targets containing Al2O3 content of 1(HA1ZO series) and 2 wt.%(HA2ZO series) on Corning glass(Eagle 2000) at substrate temperature of 150 ℃ with Ar and H2/Ar gas mixture. The effects of hydrogen addition to Al-doped ZnO(AZO) films with different Al contents on the electrical, optical and structural properties of the as-grown films as well as the vacuum- and air-annealed films were examined. Secondary ion mass spectroscopy analysis showed that the hydrogen concentration increased with increasing H2 in sputter gas. For the as-deposited films, the free carrier number in both series of HAZO films increased with increasing H2 content in sputter gas. HA2ZO film series showed better crystallinity and higher carrier concentration than HA1ZO film series. The crystallinity and the hall mobility of HA2ZO film series decreased with increasing H2 content in sputter gas, while those of HA1ZO film series showed a reversed behavior. Although HA2ZO film series yielded lower resistivity than HA1ZO film series due to higher carrier concentrations, the higher figure of merit(expressed as 1/, where and represents the resistivity and absorption coefficient, respectively) was observed for HA1ZO film series because of substantially low absorption loss in these films. Annealing at 300℃ resulted in the removal of hydrogen, causing a decrease in the carrier concentration. It was shown that hydrogen might exist as single isolated interstitial hydrogen bound with oxygen, thereby acting like an anionic dopant. Also, it was shown that the addition of hydrogen to ZnO films doped with low metallic dopant concentration could yield transparent conducting films with low absorption loss as well as with proper electrical properties, which is suitable for thin film solar cell applications.