Design of step composition gradient thin film transistor channel layers grown by atomic layer deposition

作者：Cheol Hyoun Ahn, Sohee Kim, Myeong Gu Yun, Hyung Koun Cho · 发表于：Applied Physics Letters · 年份：2014 · DOI：10.1063/1.4901732 · 被引用次数：21 · 研究领域：Thin-Film Transistor Technologies、Semiconductor materials and devices、ZnO doping and properties

In this study, we proposed the artificially designed channel structure in oxide thin-film transistors (TFTs) called a “step-composition gradient channel.” We demonstrated Al step-composition gradient Al-Zn-O (AZO) channel structures consisting of three AZO layers with different Al contents. The effects of stacking sequence in the step-composition gradient channel on performance and electrical stability of bottom-gate TFT devices were investigated with two channels of inverse stacking order (ascending/descending step-composition). The TFT with ascending step-composition channel structure (5 → 10 → 14 at. % Al composition) showed relatively negative threshold voltage (−3.7 V) and good instability characteristics with a reduced threshold voltage shift (Δ 1.4 V), which was related to the alignment of the conduction band off-set within the channel layer depending on the Al contents. Finally, the reduced Al composition in the initial layer of ascending step-composition channel resulted in the best field effect mobility of 4.5 cm2/V s. We presented a unique active layer of the “step-composition gradient channel” in the oxide TFTs and explained the mechanism of adequate channel design.