Quantum Capacitance Limited Vertical Scaling of Graphene Field-Effect Transistor

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• 作者：Huilong Xu ; Zhiyong Zhang ; Zhenxing Wang ; Sheng Wang ; Xuelei Liang ; Lian-Mao Peng
• 刊名：ACS Nano
• 出版年：2011
• 出版时间：March 22, 2011
• 年：2011
• 卷：5
• 期：3
• 页码：2340-2347
• 全文大小：958K
• 年卷期：0
• ISSN：1936-086X

文摘

A high-quality Y₂O₃ dielectric layer has been grown directly on graphene and used to fabricated top-gate graphene field-effect transistors (FETs), and the thickness of the dielectric layer has been reduced continuously down to 3.9 nm with an equivalent oxide thickness (EOT) of 1.5 nm and excellent insulativity. By measuring CV characteristics of two graphene FETs with different gate oxide thicknesses, the oxide capacitance and quantum capacitance are retrieved directly from the experimental CV data without introducing any additional fitting process and parameters, yielding a relative dielectric constant of κ = 10 for Y₂O₃ on graphene and an oxide capacitance of about 2.28 μF/cm². It is found that for a rather large gate voltage range, this oxide capacitance is comparable and sometimes even larger than the quantum capacitance of graphene. Since the total gate capacitance is determined by the smaller of the oxide and quantum capacitance, our results show that not much further improvement can be gained via further vertical scaling down of the gate oxide, suggesting that Y₂O₃ may be the ultimate dielectric material for graphene. It is also shown that the Y₂O₃ gate dielectric layer with EOT of 1.5 nm may also satisfy the ultimate lateral scaling requirement on the gate length of graphene FET and be used effectively to control a graphene FET with a gate length as small as 1 nm.