纤锌矿BeO掺Cd的电子结构与能带特性研究

采用基于密度泛函理论平面波赝势方法, 对纤锌矿BeO掺Cd的Be_1-xCd_xO合金进行电子结构与能带特性研究. 结果表明: Be_1-xCd_xO的价带顶始终由O 2p电子态决定, 而导带底由Be 2s和Cd 5s的电子态决定.随着Be_1-xCd_xO合金的Cd掺杂量增加, Cd 4d与O 2p的排斥效应逐渐加强, 同时Be_1-xCd_xO的带隙逐渐变小, 出现"直接-间接-直接"的带隙转变. 为了使理论值与实验值相一致, 对Be_1-xCd_xO带隙进行修正, 并分析了纤锌矿BeO-ZnO-CdO三元合金的带隙和弯曲系数与晶格常数的关系.

Study on the electronic structures and energy band properties of Cd-doped wurtzite BeO

The electronic structures and energy band properties of the Cd-doped wurtzite BeO are investigated by plan-wave pseudopotential method with the generalized gradient approximation in the frame of density functional theory. The theoretical results show that the valence band maximum is determined by O 2p states and the conduction band minimum is occupied by Cd 5s and Be 2s orbitals based on the total density of states and partial density of states of Be_1-xCd_xO alloy. With the Cd content x of Be_1-xCd_xO increasing, the repulsion effect between Cd 4d and O 2p states is more enhanced and the bandgap of Be_1-xCd_xO is reduced. At the same time, the bandgap undergoes the direct-indirect-direct transition. In order to obtain the theoretical values in accord with the experimental results, the bandgaps of Be_1-xCd_xO are corrected. Moreover, the relations among energy bandgap, bowing parameter and lattice constant of the wurtzite BeO-ZnO-CdO ternary alloy are analyzed.