Be和Ca掺杂纤锌矿ZnO的晶格常数与能带特性研究

Study on the lattice constants and energy band properties of Be and Ca doped wurtzite ZnO

利用密度泛函理论平面波的赝势方法,对Be、Ca掺杂纤锌矿ZnO的BexZn1-xO,CayZn1yO三元合金和BexCayZn1-xyO四元合金的晶格常数、能带特性和形成能进行计算,结果表明:BexZn1-xO晶格常数随Be掺杂量的增大线性减小,但CayZn1yO晶格常数随Ca掺杂量的增大而增大.BexZn1-xO和CayZn1-yO能带的价带顶都由O2p态电子占据,导带底由Zn4s态电子占据,其能隙随Be或Ca掺杂量的增大而变宽.由Be和Ca共掺ZnO得到的Be0.125Ca0.125Zn0.75O四元合金,其晶格常数与ZnO相匹配,能隙比ZnO大,稳定性优于Be0.25Ca0.125Zn0.625O和Be0.5Zn0.5O合金,Be0.125Ca0.125Zn0.75O/ZnO异质结构适合制作高质量ZnO基器件.

The lattice constants, energy band properties and formation energies of BexZn1-xO, CayZn1-yO and BexCauZn1-x-yO alloys of Be and Ca doped wurtzite ZnO alloys are calculated by the plan-wave pseudopotential method with GGA in density functional theory （DFF）. The theoretical results show the lattice constants of BexZn1-xO alloy decrease with Be content increasing, which is contrary to the scenario of CavZn1-yO alloy. For the energy band properties of BexZn1-xO and CauZn1-yO alloys, the valence band maxima （VBM） are determined by O 2p states and the conduction band minima （CBM） is occupied by Zn 4s states, and their band gaps are broadened when Be or Ca content is increased. The lattice constant of Be0.125Ca0.125Zn0.75O alloy of Be and Ca co-doped ZnO is matched with that of ZnO and its energy bandgap is greater than that of ZnO, so Be0.125Ca0.125Zn0.75O/ZnO structure is suitable for high-quality ZnO based device. In addition, the stability of Be0.125Ca0.125Zn0.750 alloy is also analysed.