Control of threshold voltage in ZnO-based oxide thin film transistors

• Published in: Applied physics letters 2008-07, Vol.93 (3), p.033513-033513-3
• Main Authors: Park, Jin-Seong, Jeong, Jae Kyeong, Mo, Yeon-Gon, Kim, Hye Dong, Kim, Chang-Jung
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.2963978

We investigated the feasibility of controlling the threshold voltage ( V th ) by adjusting the thickness of the active layer ( t active ) rather than by conventional chemical doping in indium-gallium-zinc oxide (IGZO) transistors with an inverted staggered structure. The value of V th of the IGZO transistor was linearly modulated from − 15.3 ± 1.6 to − 0.1 ± 0.21 V by reducing t active without any significant change in the field-effect mobility ( μ FE ) , subthreshold gate swing, or I on ∕ off ratio. The free electron density extracted from the relationship between t active and V th was 1.9 × 10 17 cm − 3 , which was consistent with the value of 1.5 × 10 17 cm − 3 obtained from the C - V measurement for the 30 - nm -thick IGZO films. The slight increase in the μ FE with increasing t active , which was in contradiction with the behavior of the corresponding amorphous Si transistor, was explained by the anomalous behavior of the source/drain contact resistance.