| Summary: | 碩士 === 國立彰化師範大學 === 光電科技研究所 === 93 === In chapter 1, I introduce the first-principles calculation based on density function theorem that may be used to deal with wave function with periodic lattice. The most important point is to treat a periodic cell possessing infinite electrons as single unit cell with finite electrons. The wave function can be expanded as a polynomial by using infinite plane wave basis. For saving the cost of calculation, the high-energy terms are neglected while the low-energy terms remain. For dealing with wave function inside the core region, pseudopotential is used to replace the coulomb potential energy of the real atoms. The effect caused by inner layer electrons is not taken into account. The effect caused by valence electrons is considered. To reduce the computation time, local density approximation is applied to deal with exchange-correlation energy between electronics. In this thesis, the solid electronic structure is calculated by using the CASTEP. Specifically, effects of model size, pseudopotential, cutoff energy and k-point of Brillouin zone are investigated.
In chapter 2, I use the CASTEP simulation software to calculate the lattice constant and band gap energy of zincblende InGaN. The results of the band gap energy and band gap bowing parameter obtained from minimized equilibrium energy method are compared with which obtained from experiment. Next, I analyze the relation between indium concentration and band gap bowing parameter of zincblende InGaN.
In chapter 3, I use the CASTEP simulation software to calculate the lattice constant and band gap energy of zincblende AlGaN. As aluminum composition increases, the band diagram of zincblende AlGaN changes from direct band gap to indirect band gap gradually. I use minimized equilibrium energy method to study the influence of lattice constant deviation on the crossover of band gap energy of zincblende AlGaN.
In the last chapter, the results obtained in this thesis are summarized.
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