= 아 래 =
1. 일 시 : 2014. 8. 25 (월), 10:30 ~
2. 장 소 : 신소재 공학과 2429호
3. 연 사 : 김 현 석 교수(충남대학교 재료공학과)
4. 제 목 : 차세대 디스플레이 응용을 위한 고이동도, 고신뢰성 산화물 박막 트랜지스터 기술
Increasing demands for high performance transistors for flat panel displays have led to the development of high mobility metal oxide based semiconductors such as In-Ga-Zn-O (IGZO). Thin-film transistors (TFTs) that use such materials have field effect mobility exceeding 10 cm2/Vs, and are suitable for AMLCDs with ultra definition (4000 x 2000), large size (> 70 inch). However, display technology is now oriented towards AMOLED displays, which need driving transistors with higher field effect mobility. In this work, an alternative type of high mobility semiconductor, zinc oxynitride (Zn-O-N), is studied by both theoretical calculations and experimental evaluation of thin films and TFT devices. Hall measurements of reactively sputtered Zn-O-N films indicate that the material is n-type. First principles density functional theory (DFT) calculations are performed to examine the carrier effective mass in pure zinc nitride (Zn3N2), and nitrogen vacancies (VN) are found to be the most dominant shallow donor-like defects. It is shown that doping with metal cations that form a stronger bond with nitrogen leads to the suppression of free carriers, which is confirmed experimentally by doping high mobility Zn-O-N films with gallium (Ga) and aluminum (Al). Thin film transistor devices fabricated using both undoped and Ga-doped Zn-O-N further show such defect reduction, resulting in decreased off-currents and subthreshold swing.