N-MOSFETs Formed on Solid Phase Epitaxially Grown GeSn Film with Passivation by Oxygen Plasma Featuring High Mobility

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• 作者：Yung-Chin Fang ; Kuen-Yi Chen ; Ching-Heng Hsieh ; Chang-Chia Su ; Yung-Hsien Wu
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：December 9, 2015
• 年：2015
• 卷：7
• 期：48
• 页码：26374-26380
• 全文大小：384K
• ISSN：1944-8252

文摘

Solid phase epitaxially grown GeSn was employed as the platform to assess the eligibility of direct O₂ plasma treatment on GeSn surface for passivation of GeSn N-MOSFETs. It has been confirmed that O₂ plasma treatment forms a GeSnO_x film on the surface and the GeSnO_x topped by in situ Al₂O₃ constitutes the gate stack of GeSn MOS devices. The capability of the surface passivation was evidenced by the low interface trap density (D_it) of 1.62 脳 10¹¹ cm^鈥? eV^鈥?, which is primarily due to the formation of Ge鈥揙 and Sn鈥揙 bonds at the surface by high density/reactivity oxygen radicals that effectively suppress dangling bonds and decrease gap states. The good D_it not only makes tiny frequency dispersion in the characterization of GeSn MOS capacitors, but results in GeSn N-MOSFETs with outstanding peak electron mobility as high as 518 cm²/(V s) which outperforms other devices reported in the literature due to reduced undesirable carrier scattering. In addition, the GeSn N-MOSFETs also exhibit promising characteristics in terms of acceptable subthreshold swing of 156 mV/dec and relatively large I_ON/I_OFF ratio more than 4 orders. Moreover, the robust reliability in terms small V_t variation against high field stress attests the feasibility of using the O₂ plasma-treated passivation to advanced GeSn technology.