Comparative Study of Atomic Layer Deposited Indium-Based Oxide Transistors with a Fermi Energy Level-Engineered Heterojunction Structure Channel through a Cation Combinatorial Approach
- Authors
- Cho, Min Hoe; Choi, Cheol Hee; Jeong, Jae Kyeong
- Issue Date
- Apr-2022
- Publisher
- American Chemical Society
- Keywords
- atomic layer deposition; heterojunction; high mobility; high-κ dielectric; indium gallium zinc oxide; low operation voltage; thin-film transistor
- Citation
- ACS Applied Materials and Interfaces, v.14, no.16, pp.18646 - 18661
- Indexed
- SCIE
SCOPUS
- Journal Title
- ACS Applied Materials and Interfaces
- Volume
- 14
- Number
- 16
- Start Page
- 18646
- End Page
- 18661
- URI
- https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/138801
- DOI
- 10.1021/acsami.1c23889
- ISSN
- 1944-8244
- Abstract
- Amorphous indium-gallium-zinc oxide (a-IGZO) has become a standard channel ingredient of switching/driving transistors in active-matrix organic light-emitting diode (AMOLED) televisions. However, mobile AMOLED displays with a high pixel density (≥500 pixels per inch) and good form factor do not often employ a-IGZO transistors due to their modest mobility (10-20 cm2/(V s)). Hybrid low-temperature polycrystalline silicon and oxide transistor (LTPO) technology is being adapted in high-end mobile AMOLED devices due to its ultralow power consumption and excellent current drivability. The critical issues of LTPO (including a complicated structure and high fabrication costs) require a search for alternative all-oxide thin-film transistors (TFTs) with low-cost processability and simple device architecture. The atomic layer deposition (ALD) method is a promising route for high-performance all-oxide TFTs due to its unique features, such as in situ cation composition tailoring ability, precise nanoscale thickness controllability, and excellent step coverage. Here, we report an in-depth comparative investigation of TFTs with indium-gallium oxide (IGO)/gallium-zinc oxide (GZO) and indium-zinc oxide (IZO)/GZO heterojunction stacks using an ALD method. IGO and IZO layers with different compositions were tested as a confinement layer (CL), whereas the GZO layer was used as a barrier layer (BL). Optimal IGO/GZO and IZO/GZO channels were carefully designed on the basis of their energy band properties, where the formation of a quasi-two-dimensional electron gas (q2DEG) near the CL/BL interface is realized by rational design of the band gaps and work-functions of the IGO, IZO, and GZO thin films. To verify the effect of q2DEG formation, the device performances and stabilities of TFTs with CL/BL oxide heterojunction stacks were examined and compared to those of TFTs with a single CL layer. The optimized device with the In0.75Zn0.25O/Ga0.80Zn0.20O stack showed remarkable electrical performance: μFEof 76.7 ± 0.51 cm2/(V s), VTHof -0.37 ± 0.19 V, SS of 0.13 ± 0.01 V/dec, and ION/OFFof 2.5 × 1010with low operation voltage range of ≥2 V and excellent stabilities (ΔVTHof +0.35, -0.67, and +0.08 V for PBTS, NBIS, and CCS, respectively). This study suggests the feasibility of using high-performance ALD-derived oxide TFTs (which can compete with the performance of LTPO transistors) for high-end mobile AMOLED displays.
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