The Study On Band Structure Of Si-based Strained Materials

There has been a lot of interest in the Si-based (Si,SiGe) strained materials lately with its advantage of high-mobility, adjustable band structure and compatible technology with traditional silicon processing and wide application in the high-speed and high-performance devices and circuits. The band structure is the theoretical basis of the research on the base attribute and the design of the high-speed and high-performance devices and circuits. However, Up to now there have been few reported results for the band structure of the Si-based strained materials. Based on the basic physical mechanism of the Si-based strained materials, system study on the band structure has essential theoretical significance and practical value.Based on an analysis of symmetry under strain, the number of equivalent CB edge energy extrema is presented. Using K·P method with the help of perturbation theory, E(k)-k relation near minima CB energy followed from linear deformation potential theory is determined, from which the parameters extracted, namely, the position of the extremal point, the electronic effective masses are obtained. With the frame of K·P theory, the E(k)-k relation has been derived by taking strained Hamiltonian perturbation into account. The corresponding model were obtained such as the energy level of first valence band, second valence band and spin-orbit splitting band at theΓposition and the hole effective mass along arbitrarily k wavevector direction. The band structure model is applicable for the Si-based strained materials on arbitrarily oriented substrate and essensail to the investigation into the performance enhancement of the Si-based strained materials and devices.Using the parameters of band structure, the models of density-of-states effective mass, density-of-states and intrinsic carrier concentration of the conduction band and valence band were obtained. The models are the key parameters of the investigation into the electricity property of the Si-based strained materials and devices.The physical structure models of strained Si used for CASTEP calculation were specified. How to calculate the band structures of strained Si by CASTEP approach was discussed. As an assistant means, the CASTEP approach can be used for the investigation into the band structure and other basic physical properties of the Si-based strained materials.Based on Hook law, the transformation model between Ge fraction and stress was established, which makes the band structure and other basic physical properties of the Si-based strained materials characterized by stress and broadens the scope of the application of the research results.