Seong Han-Kyu, Jeon Eun-Kyoung, Kim Myoung-Ha, Oh Hwangyou, Lee Jeong-O, Kim Ju-Jin, Choi Heon-Jin
Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, Korea.
Nano Lett. 2008 Nov;8(11):3656-61. doi: 10.1021/nl8016362. Epub 2008 Oct 28.
This study reports the electrical transport characteristics of Si(1-x)Gex (x=0-0.3) nanowires. Nanowires with diameters of 50-100 nm were grown on Si substrates. The valence band spectra from the nanowires indicate that energy band gap modulation is readily achievable using the Ge content. The structural characterization showed that the native oxide of the Si(1-x)Gex nanowires was dominated by SiO2; however, the interfaces between the nanowire and the SiO2 layer consisted of a mixture of Si and Ge oxides. The electrical characterization of a nanowire field effect transistor showed p-type behavior in all Si(1-x)Gex compositions due to the Ge-O and Si-O-Ge bonds at the interface and, accordingly, the accumulation of holes in the level filled with electrons. The interfacial bonds also dominate the mobility and on- and off-current ratio. The large interfacial area of the nanowire, together with the trapped negative interface charge, creates an appearance of p-type characteristics in the Si(1-x)Gex alloy system. Surface or interface structural control, as well as compositional modulation, would be critical in realizing high-performance Si(1-x)Gex nanowire devices.
本研究报告了Si(1-x)Gex（x = 0 - 0.3）纳米线的电输运特性。直径为50 - 100 nm的纳米线生长在硅衬底上。纳米线的价带光谱表明，利用锗含量很容易实现能带隙调制。结构表征显示，Si(1-x)Gex纳米线的原生氧化物以SiO2为主；然而，纳米线与SiO2层之间的界面由硅和锗的氧化物混合物组成。纳米线场效应晶体管的电学表征显示，由于界面处的Ge - O和Si - O - Ge键，在所有Si(1-x)Gex组成中均表现出p型行为，相应地，在充满电子的能级上有空穴积累。界面键也主导迁移率以及导通和截止电流比。纳米线的大界面面积，加上捕获的负界面电荷，在Si(1-x)Gex合金系统中产生了p型特性的表象。表面或界面结构控制以及成分调制对于实现高性能Si(1-x)Gex纳米线器件至关重要。
