GaN中与C和O有关的杂质能级第一性原理计算

用局域密度泛函线性丸盒轨道大型超原胞方法(32个原子),对纯纤锌矿结构的GaN用调节计算参数(如原子球与“空球”的占空比)在自洽条件下使Eg的计算值(323eV)接近实验值(35eV).然后以原子替代方式自洽计算杂质能级在Eg中的相对位置.模拟计算了六角结构GaN中自然缺陷以及与C和O有关的杂质能级位置,包括其复合物.计算结果表明,单个缺陷如镓空位VGa、氮空位VN、氧代替氮ON、炭代替氮CN、炭代替镓CGa等与已有的计算结果基本一致.计算结果表明杂质复合物会导致单个杂质能级位置的相对变化.计算了CNON,CGaCN,CNOV和CGaVGa,其中CNON分别具有深受主与浅施主的特征,是导致GaN黄光的一种可能的结构. 关键词： GaN 杂质能级 电子结构

Ab initio calculation of the electronic structure of carbon and oxygen impurities in GaN

Firstly we use the ab initio calculation with local density function-linear muffin tin orbital methods combined with a supercell(32atoms) to examine pure wurtzite GaN, and obtain the calculated E g value (3.23eV) for pure GaN close to that of experimental value by modifying the calculated parameter (for example, the proportion of atomic sphere and empty sphere). Then we examine the inpurity energy level by substituting the impurities for gallium or nitrogen or vacancy. We calculate the energy level of the intrinsic defect, the carbon and oxygen impurities, and their complexes in wurtzite GaN. The results show that the densities of states (DOS) for mono-defects, e.g. vacancy of gallium V Ga, vacancy of nitrogen V N, oxygen substitute for nitrogen O N, carbon substitute for nitrogen C N, and carbon substitute for gallium C Ga are consistent with previous calculations. However, the energy level of the complex is not the simple plus of mono-defects, and complexes can change the mono-defect level. The complex composed of the substituted carbon and oxygen onto nitrogen sites has the character of shallow donor and deep acceptor. This is likely to responsible for the yellow luminescence band.