Research On Hole Mobility Of Strained-Si/Strained-SiGe

Si based strained material (strained Si, strained SiGe) can improve the device performance due to the enhanced carrier mobility, and has great application prospects in high speed / high performance devices and circuits. In this paper, we mainly focus on the hole mobility of Strained Si/Strained SiGe material.In this paper, we focus on the hole mobility of Strained Si/Strained SiGe material. Firstly, the formation mechanism of Strained Si/Strained SiGe, and the effect of stress of different type on band structure of bulk Si has been analyzed, and the research on how hole mobility of Strained Si/Strained SiGe being enhanced has been done. Based on the K.P theory, combined with the band structure models of Strained Si/Strained SiGe materials, parameters such as density of state effective mass and conductivity effective mass of typical orientations in (001),(101),(111) planes, necessary to solve mobility, were obtained.Secondly, based on the quantum mechanical theory, several kinds of hole scattering mechanisms in valence band, including ionized impurity scattering, acoustical phonon scattering, non polar optical phonon scattering and alloy scattering which is only in Strained SiGe material, have been specifically analyzed, and the corresponding models of hole scattering are set up. With average relaxation time method, the total hole scattering rate, which is different of planes mentioned above in Strained Si/Strained SiGe material, were obtained respectively, then the mobilities which show a high degree of anisotropy were obtained.Finally, the research on the hole mobility of Strained Si/Strained SiGe material, as a function of Ge content and doping concentration, has also been done with MATLAB simulation tool. The results show that the hole mobility of Strained Si/Strained SiGe increase significantly with increasing Ge fraction. Moreover, the hole mobilities of different planes are different, and the hole mobilities of different orientations are highly anisotropic in the same plane. The hole mobilities obtained in this paper are quantitative, and hence can supply valuable references to the conduction channel design related to the stress and orientation in the Si based strained PMOS devices.