BexZn1-xO1-ySy四元合金热力学性质的第一性原理研究

First-principles study of thermodynamic properties of Be x Zn 1-x O 1-y S y quaternary alloys

通过等价阳离子如Be,Mg,Cd等部分取代Zn,同时共掺杂等价阴离子S取代O形成四元合金来调控ZnO带隙是目前ZnO能带研究的热点.四元合金中,Be的掺杂可以增加ZnO的禁带宽度,同时掺杂S可以降低晶格畸变,使BexZn1-xO1-ySy(BeZnOS)合金在光电器件领域具有潜在的应用价值.利用第一性原理计算,研究纤锌矿(WZ)、闪锌矿(ZB)和岩盐矿(RS)相BeZnOS合金不同Be、S掺杂含量下各种构型的形成能、电子结构、热力学性质等.通过对BeZnOS合金的吉布斯自由能求出了在T=0 K时随掺杂Be和S含量变化的组分相图(随着Be、S的掺杂含量增加,BeZnOS合金在纤锌矿-闪锌矿-岩盐矿三相间转变.计算得到的溶解度间隙岛给出了BeZnOS合金的理论固溶极限,同时也计算出了WZ-,RS-和ZB-BeZnOS四元合金随成分变化的带隙调控的范围.这些为实验上得到高质量不同相结构的BeZnOS四元合金薄膜提供了理论支持,同时也为高性能光电探测器的应用提供有益参考.

At present,the focus of ZnO band engineering researches is to adjust the ZnO band gap by forming quaternary alloys,which are formed by partially replacing Zn with equivalent cations such as Be,Mg,Cd,etc.,and co-doping the equivalent anion S to replace O.In the quaternary alloys,the doping of Be can increase the band gap of ZnO,and the co-doping of S can reduce the lattice distortion,so that the BexZn1-xO1-ySy(BeZnOS)alloys have potential application value in the field of photovoltaic devices.In this paper,the formation energies,electronic structures and thermodynamic properties of various configurations of wurtzite(WZ),zincblende(ZB),and rocksalt(RS)phase BeZnOS alloys with different doping contents of Be and S are calculated by the first-principles calculation.The compositional phase diagram at T=0 K and the miscibility gap islands were obtained from the Gibbs free energy and mixing entropy of BeZnOS alloys.With the increasing the content of Be and S,the BeZnOS alloy undergoes phase transition between wurtzite-zincblende-rocksalt.Moreover,the range of band gap regulation of WZ-,RS-and ZB-BeZnOS quaternary alloys with composition changes was calculated.These provide theoretical support for experiments of obtaining high-quality BeZnOS quaternary alloy,and also provide useful references for the application of high-performance photodetectors.