【作者】 韩冬；

【导师】 孙洪波；

【作者基本信息】 吉林大学 ， 微电子学与固体电子学， 2009， 硕士

【摘要】 把石英晶体这种传统上的绝缘体材料当作半导体材料来研究是一个开拓石英晶体新应用领域的工作,也是半导体技术研究的一个趋势。石英晶体的掺杂特性分析十分重要,其掺杂特性的表征对研究其它宽禁带半导体材料掺杂特性同样具有指导意义。本论文的核心工作是应用基于密度泛函理论的第一性原理方法来计算石英晶体的掺杂特性。这些杂质包括三主族元素、五主族元素分别替硅位所产生的P型杂质和N型杂质,五主族元素替氧位所产生的P型杂质。随着掺杂超胞电荷变化,替硅位三主族元素杂质(B, Al, Ga)与邻近的四个氧原子键长变化不明显,电子呈现非局域特性;替硅位的五主族元素杂质(N, P, As)与邻近的四个氧原子键长随着掺杂超胞的电荷增加(体系增加电子)而变长,电子呈现明显的局域特性。五族元素替氧位后,杂质与周围的邻近硅的键长随着掺杂超胞的电荷增加而变短,同样电子呈现局域特性。替位元素进行的掺杂在石英晶体体系中都有较高的形成能。杂质在石英晶体中会产生相对浅的受主能级和较深的施主能级。三族元素(B, Al, Ga)替硅位在Alpha-SiO2中形成的受主缺陷能级分别处于价带顶之上0.47eV、0.34eV、0.27eV的位置。计算得到五族元素(N, P, As)替硅位产生的施主杂质缺陷能级分别处于价带顶之上4.00eV、6.08eV、3.60eV的位置。五族元素(N, P, As)替氧位产生的受主杂质缺陷能级分别处于价带顶之上1.59eV、3.17eV、3.45eV的位置。石英晶体所表现出来的非对称掺杂特性和宽禁带半导体所体现的非对称掺杂特性相同。更多还原

【Abstract】 Quartz material is on of the most common mineral. It is of stable properties in both physics and chemistry. Quartz material which effects our daily lives is used widely. In Stone Age, people have begun to make stone axes and stone arrows with quartz. They use the simple production tools to hunt for food and fight against the enemy.The quartz material has been researched extensively with the development of modern science and technology. People made a variety of devices based on its optical and electrical properties. The research on quartz properties and application of quartz material are changing our life tremendously and promoting the social progress greatly. Therefore,exploring the new application field of quartz material is very important.With the rapid development of microelectronics industry, the semiconductor materials require a wide bandgap, high fire-resistant, high mobility. Research on semiconductor’s properties, especially doping property on wide bandgap semiconductor materials is of great significance. Therefore, quartz crystal doping property analysis is very important and Research on quartz doping property helps us to research the doping property of other wide bandgap materials.The main work in this paper is to explore the doping characteristics of silicon dioxide in atomic and electronic scale. The method is first-principles calculation based on Density Functional Theory (DFT).Characterizing the property of materials using first principle based on DFT, calculating the multi-electron system composed of hundreds of atoms, solving the Schr?dinger equation exactly, and computing the system total energy, are not an easy task. Considering the complexity and accuracy of system computing, Not only the calculation time is not tolerable, but also storage is not provided for computing data, if we use personal computer (PC) as the computing environment. However, the supercomputer can provide both abundant storage and little computing time consumption, but computing cost is so high that we can’t offer it. Supercomputer is not suitable in our research. Therefore, considering our research, building a suitable parallel computing environment is problem we must solve firstly. After analyzing the components of parallel computing system, in the tolerable computing time consumption, we confirm Cluster which is composed of PC, gigabit Ethernet, TCP/IP and MPI as our parallel computing environment. This combination is low cost, efficient, mature and easy to assemble. We have tested the eight-node parallel computing environment based on Intel Q6600 processor. The highest linpack mark of this parallel computing environment is 185.1Gflops. The efficiency of eight-node parallel computing is 74%. It is a good parallel efficiency. The parallel computing environment has an effective parallel computing acceleration in practical tasks and meets the requirement of the theoretical calculation.The core work in this paper is to explore the doping characteristics of alpha-quartz crystal using first principle based on DFT. These impurities doping in alpha-quartz crystal include theⅢA elements (P-type),ⅤA elements (N-type) substituting silicon atom andⅤA elements (P-type) substituting oxygen atom.After calculation, we find the bond length change differently. The bond length between the impurity ofⅢA elements (B, Al, Ga) substituting silicon atom and the four neighboring oxygen atoms doesn’t change significantly with the charge change of the doping supercell. The electron around the impurity is delocalized. The bond length between the impurity thatⅤA elements (N, P, As) substituting silicon atom and the four neighboring oxygen atoms gets longer with the charge of the doping supercell is increasing. The electron around the impurity is localized. The bond length between the impurity thatⅤA elements (N, P, As) substituting oxygen atom and the neighboring silicon atoms get shorter with the charge of the doping supercell is increasing. We explain the bond length change differently with the change of Coulomb interaction among atoms and the redistribution of electron density.We also calculate the formation energy of impurities in alpha-quartz in this paper. The substituting impurities in alpha-quartz have a relative high formation energy according to the formation energy formula. This is due to the larger distance between crystal atoms, impurity atoms tend to be interstitial site rather than the lattice. We calculate the defect levels in bandgap using the impurity formation energy. The result show that quartz has a tendency of asymmetric doping characteristic, i.e. shallow acceptor and deep donor. The defect levels E(-1/0) ofⅢA elements (B, Al, Ga) substituting silicon atom is 0.47eV, 0.34eV and 0.27eV above the valence band maximum (VBM), respectively. The defect levels E(+1/0) ofⅤA elements (N, P, As) substituting silicon atom is 4.00eV, 6.08eV and 3.60eV above the VBM, respectively. The defect levels E(-1/0) ofⅤA elements (N, P, As) substituting oxygen atom is 1.59eV, 3.17eV and 3.45eV above the VBM, respectively. The alpha-quartz crystal has a doping polarity as other wide bandgap materials have.更多还原