纤锌矿Beo掺Cd的电子结构与能带特性研究

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

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-x)Cd_xO合金进行电子结构与能带特性研究.结果表明:Be_(1-x)Cd_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-x)Cd_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-x)Cd_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-x)Cd_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.

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 Be1-xCdxO alloy. With the Cd content x of Be1-xCdxO increasing, the repulsion effect between Cd 4d and O 2p states is more enhanced and the bandgap of Be1-xCdxO 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 Be1-xCdxO are corrected. Moreover, the relations among energy bandgap, bowing parameter and lattice constant of the wurtzite BeO-ZnO-CdO ternary alloy are analyzed.