GaN(110)表面原子及电子结构的第一性原理研究

First Principile Study on the Atomic and Electronic Structure of GaN(110)

用缀加平面波加局域轨道方法计算了立方GaN及其非极性 ( 1 1 0 )表面的原子结构和电子结构 ,得到的GaN晶格常数及体积弹性模量与实验值符合得很好 .用层晶超原胞模型计算立方GaN ( 1 1 0 )表面的原子和电子结构 ,发现表面顶层原子发生键长收缩并旋转的弛豫特性 ,表面阳离子向体内移动 ,与周围阴离子形成sp2 杂化 ,而表面阴离子则形成p3 型锥形结构 .其面旋角为 1 4 .1°,比传统的Ⅲ V族半导体 ( 1 1 0 )表面面旋角 ( 30°± 2°)小得多 ,这主要与材料的离子性有关 .此外 ,在带隙附近还发现了两个表面态 ,一个是占据的表面态 ,主要是由N的p电子构成的 ;另一个是空态 ,主要由阳离子的轨道构成 .在驰豫后 ,这两个表面能带都移出带隙 ,分别进入导带和价带 。

With the Augmented Plane Wave and local orbital (apw+lo) method the atomic structure and electronic structure of the (110) surface of cubic GaN as calculated. Different exchange correlation potentials were used to compare the results of bulk,and the results are in excellent agreement with the experiment data. Using the slab and supercell model we caculated the atomic and electronic structure of the (110) surface of cubic GaN. In our results the cation moved inward, and tended to a planar sp 2-like bonding situation with its three N neighbors, and N atoms tended to a taper p 3-like bonding with its three Ga neighbors. This relaxation is analogous to that of Ⅲ-V semiconductor (110) surface. Meanwhile, we found two surface states at the band edge, one being an occupied resonating surface state, which is composed mostly of p electrons of N atoms, the other an unoccupied state, which is composed mostly of the orbitals of Ga atoms.