期刊
APPLIED SURFACE SCIENCE
卷 556, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.apsusc.2021.149676
关键词
Amorphous oxide semiconductors; Work function; Carrier density; Thin film transistors; Indium oxides; InAlZnO
类别
资金
- U.S. National Science Foundation (NSF) [ECCS-1931088]
- Purdue University
- Purdue Research Foundation [60000029]
- Polytechnic RDE SEED program
- Basic Science Research Program through the NRF Korea - Ministry of Science and ICT [NRF-2018R1A2B6002194]
- Improvement of Measurement Standards and Technology for Mechanical Metrology by KRISS [20011028]
This study investigates the origin of carrier density modulation in InAlZnO (IAZO), finding that the carrier density of IAZO can be significantly increased through low temperature annealing. Additionally, high-pressure oxidation experiments reveal that the equilibrium carrier density of IAZO is much higher than those typically used in TFT channel applications.
In thin film transistors (TFTs), carrier density in the channel layer is a fundamental intrinsic factor to engineer desirable TFT performance parameters such as the threshold voltage, drain current, and on-to-off ratio. Here, we report on the origin of carrier density modulation in a ternary cation system of InAlZnO (IAZO) and its effect on the TFT performance. Through work function investigations and bandgap analysis, the carrier density of IAZO is found to be increased by >10(4) times compared to that of unannealed IAZO after low temperature annealing at 200 degrees C in air. Photoelectron spectroscopic studies reveal that no significant changes were made in dopant concentrations, neither intrinsic (vacancy-based native defect) nor extrinsic (cation substitution) after annealing. From high pressure oxidation with much enhanced reactivity of reaction gases, it is identified that the equilibrium carrier density of IAZO is much higher than those used in typical TFT channel application. The low channel carrier density tends to increase and reach the higher equilibrium carrier density in the absence of kinetic constraints. This notion is further supported by a defect-state transition mechanism. The combinatorial investigations presented herein help understand the origin of the unintentional increase in channel carrier density in amorphous oxides and its effect on the operation of TFTs.
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