The Study On Band Structures Of Si-based Strained Materials

Strained Si has the advantages of high-mobility and adjustable energy-band structure, and its processing technology can also be compatible with traditional silicon technology. In modern semiconductor industry, numbers of heterojuction devices and circuits of strained Si have been put into practical use. Simultaneously, the theoretical researches concerning strained Si also developed. For energy band determines lots of significant properties of semiconductor materials, a lot of relevant theories, which included Density-Function Theory (DFT), Pseudopotential Theory (PPT), and k·p Perturbation Theory, have developed since 1950s. The study on energy band of bulk Si (relaxed Si) has been launched for long time, however, the influence of strain on energy band of Si has not been investigated systemically. So that influences of both biaxial tensile strain and compressive strain on energy band of Si and SiGe will be studied in this thesis.Based on k·p Perturbation Theory in this paper, the classical 6×6 Hamiltonian Matrix was adopted as well as the spin-orbit split term introduced for the purpose of getting the valence band structure of unstrained Si. In addition to the terms above, the strain perturbation term was taken into consideration to get the valence band structure of strained Si. Two kinds of strain terms were discussed, and some numerical calculation work was also done in order to attain the expression. Compared to the results in some references, the calculation was right, and the trend of valence band's changing under strain was also correct.The way to solve the conduction band of strained Si was also illustrated in this paper.