单轴110应力硅电子迁移率

Electron Mobility in Silicon Under Uniaxial110 Stress

  • 摘要: 基于k·p微扰法研究单轴110应力作用下硅的导带结构,获得单轴110应力硅的导带底能量及电子有效质量.在此基础上,考虑电子谷间、谷内及电离杂质散射,采用弛豫时间近似计算单轴110应力硅沿不同晶向的电子迁移率.结果表明:单轴110应力作用下硅的电子迁移率具有明显的各向异性.在001、110及110输运晶向中,张应力作用下电子沿110晶向输运时迁移率有较大的增强,由未受应力时的1 450 cm2·Vs-1提高到2 GPa应力作用下的2 500 cm2·Vs-1.迁移率增强的主要原因是电子有效质量的减小,而应力作用下硅导带能谷分裂导致的谷间散射几率的减小对电子迁移率的影响并不显著.

     

    Abstract: Conduction band structure of silicon under uniaxial110 stress is studied with two band k·p perturbation theory. Splitting energy of conduction band minima and electron effective mass as a function of stress and direction electron mobility in uniaxial stressed silicon are obtained with relax time approximate theory. Intervalley scattering, intravalley scattering, and ionized impurity scattering are considered in calculation. It is demonstrated that as uniaxial110 stress is applied on silicon crystal, a significant anisotropy in electron mobility can be observed. Among crystal directions001, 110, and110, electron mobility along110 direction under uniaxial110 tensile stress has a profound enhancement, which increase from 1 450 cm2·Vs-1 to 2 500 cm2·Vs-1 as stress change from 0 to 2 GPa. Electron mobility enhancement is mainly due to uniaxial stress induced conduction effective mass reduction, while suppression of intervalley scattering plays a minor role.

     

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