High-Performance p-Type Black Phosphorus Transistor with Scandium Contact

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• 作者：Ling Li ; Michael Engel ; Damon B. Farmer ; Shu-jen Han ; H.-S. Philip Wong
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：April 26, 2016
• 年：2016
• 卷：10
• 期：4
• 页码：4672-4677
• 全文大小：386K
• 年卷期：0
• ISSN：1936-086X

文摘

A record high current density of 580 μA/μm is achieved for long-channel, few-layer black phosphorus transistors with scandium contacts after 400 K vacuum annealing. The annealing effectively improves the on-state current and I<sub>onsub>/I<sub>offsub> ratio by 1 order of magnitude and the subthreshold swing by ∼2.5×, whereas Al<sub>2sub>O<sub>3sub> capping significantly degrades transistor performances, resulting in 5× lower on-state current and 3× lower I<sub>onsub>/I<sub>offsub> ratio. The influences of moisture on black phosphorus metal contacts are elucidated by analyzing the hysteresis of 3–20 nm thick black phosphorus transistors with scandium and gold contacts under different conditions: as-fabricated, after vacuum annealing, and after Al<sub>2sub>O<sub>3sub> capping. The optimal black phosphorus film thickness for transistors with scandium contacts is found to be ∼10 nm. Moreover, p-type performance is shown in all transistors with scandium contacts, suggesting that the Fermi level is pinned closer to the valence band regardless of the flake thickness.