| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 93 === The applications of the Si and GaAs have been getting more and more important in the semiconductor industry. With the feature of Si and GaAs, it has been applied more extensively in the semiconductor field. Therefore, knowing the physical properties of these materials in detail becomes the crucial issue to develop the semiconductor industry. The objective of this thesis is to study the effects of strainsand temperature on the band structures of Si and GaAs by the fhi98md, which is built on the density functional theory(DFT). This constitutes a method in which without loss of rigor one work with electron density as the basic varible, instead of the wave function. The local density approximation(LDA) uses the uniform-electron gas formula for exchange and correlation energy. The pseudopotential approximation removes the core electrons and by replacing them and the strong ionic potential by a weaker pseudopotential that acts on a ser of pseudo wave functions rather than the true valence wave functions. By using above methods, we will discuss the effect of energy gap with respect to the strain and temperature in this thesis. Moreover, we will also simulate the variation of the lattice constant from different temperature in equilibrium state.
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