【作者】 伍剑明；

【导师】 赵宇军；

【作者基本信息】 华南理工大学 ， 材料物理与化学， 2014， 博士

【摘要】 半导体材料的不断创新与现代信息产业日新月异般的发展是息息相关的。半导体材料按其组成元素所在的元素周期表位置大致可分为Ⅱ-Ⅵ族、III-V族、IV族、IV-VI族和II-IV-VI族等几大类体系。其中，Ⅱ-Ⅵ族半导体由于具有直接带隙、发光频率覆盖范围广、容易实现等价掺杂等特点最早被人关注。传统的Ⅱ-Ⅵ族半导体包括由II族元素Zn、Cd、Hg和VI族元素S、Se、Te、O等组成的二元或者三元单晶化合物。与传统的体系相比，3d过渡金属基Ⅱ-Ⅵ族半导体可能具有磁学方面的性质，从而表现出其特有的自旋输运和磁光耦合等新特性。在半导体材料制备的过程中，往往会有意地往体系里掺入各种不同的杂质，以便调控半导体的发光特性和输运特性等。同时，在现有的实验室制备条件下，得到的半导体样品普遍会存在各种各样的晶体缺陷。如何有效的控制这些杂质和缺陷的形成与分布，是半导体功能材料设计的最基本的问题。相比于其它理论方法研究，第一性原理计算方法不依赖于任何经验参数，能从电子结构层面上去模拟、解释各种材料性质的微观起源，同时还能对各种材料在结构与性能方面进行预测，起到指导实验方法的作用，越来越受到科研人员广泛的认同和器重。本文正是基于第一性原理计算方法模拟利用3d过渡金属对包括ZnTe、MnTe、CdTe等体系进行阳离子位的替代掺杂，研究其相关杂质相在晶体内的分布情况以及杂质相之间的磁性耦合等性质。另外，我们也对纤锌矿结构的CoO和MnO体系中本征缺陷的形成情况以及其对体系的载流子特性的影响做了系统的研究。本论文章节安排如下：在第一章，我们会对传统Ⅱ-Ⅵ族半导体和3d过渡金属基Ⅱ-Ⅵ族半导体的研究现状作一个系统的介绍。在第二章，我们会详尽地介绍密度泛函理论的理论基础。第三章主要介绍了利用3d过渡金属对包括ZnTe、MnTe、CdTe三种体系进行阳离子位的替代掺杂的相关性质的研究。我们发现MnTe基底的Mn反铁磁背景对掺杂过渡金属杂质的团簇化趋势有显著的减弱作用(Ni除外)，同时使得Fe、Co和Ni杂质之间的磁耦合作用得到了有效增强。其中Fe掺杂到MnTe时，能同时实现团簇化趋势减弱与磁耦合增强的效果，预示着利用基底的反铁磁背景对掺杂过渡金属杂质的作用，能有效促进发展具有高居里温度的本征稀磁半导体材料。第四章主要介绍了基于纤锌矿结构CoO和MnO体系中的本征缺陷相关性质的研究结果。对于纤锌矿结构MnO体系，我们发现通过改变生长环境中的氧偏压，就能实现对其的p/n型导电性能调控。其中富氧环境对应的是p型导电，主要形成的缺陷包括Oi、Oi+OMn、OMn和VMn；而贫氧环境则对应n型导电，主要形成的缺陷包括VO、MnO、Mni和VO+Mni。对于纤锌矿结构CoO而言，体系很容易被设计成为p型导电，但很难实现n型导电。我们预期纤锌矿结构MnO体系的可调p/n导电特性会给六方结构的半导体材料带来更多新的应用前景。第五章会简单介绍目前进行的工作与未来的工作展望。最后是本论文的总结，其后会列出本论文相关的参考文献以及博士期间所取得的工作成果。更多还原

【Abstract】 The rapid development of modern information industry is intensively related to thecontinuous innovation of semiconductor materials. According to the locations of theircomponents in the periodic table, semiconductors can be categorized into IV, Ⅱ-Ⅵ, III-V, IV-VI, and II-IV-VI etc. Among them, the Ⅱ-Ⅵ semiconductor received people’s attention at thevery beginning due to their unique properties of direct band gaps, wide range of light emittingfrequencies, easy practice of isovalent doping and so on. Traditional semiconductors containthe binary or ternary compounds consisted of the group II (Zn, Cd, and Hg) and group VI (S,Se, Te, and O) elements. Compared with the tradition systems, the3d transition metal (3d TM)based Ⅱ-Ⅵ semiconductors may couple with magnetic characteristics, and thus show newproperties, e.g. the unique spin transport and the magneto-optic coupling.During the preparation, various dopants are often deliberately introduced into thesemiconductor systemswith the purpose oftuning their optical and transport characters.Meanwhile, in general, it is hard to exclude all of the crystal defects as the samples preparedunder the lab conditions. It has been the most fundamental issue for semiconductor functionaldesigns to make clear how to effectively utilize the formation and distribution of the potentialdopants and defects. Compared with other simulation methods, the first-principles calculations,on one hand, do not depend on any empirical parameter, and are able to simulate and explainthe properties ofvarious materials at the electronic level. On the other hand, they are capable ofpredicting structural and other properties in various kinds of materials, being the guide forexperimental approaches, and really attracted more and more attentions by scientificresearchers.Based on the first-principles calculations, we will study the structural and the couplingproperties of the doped systems of ZnTe:TM, CdTe:TM and MnTe:TM. We have alsoinvestigated the defect formations and their influences on the carrier characters of wurtzite (wz)CoO and MoO.The arrangements of this dissertation are as follows:In Chapter One, a systematic introduction will be given on the research background of the traditional Ⅱ-Ⅵ and3d-TM based Ⅱ-Ⅵ semiconductors. In Chapter Two, we will specificallyintroduce the theoretical foundations of the density functional theory (DFT).Chapter Three mainly introduce the researches of the structural and the coupling propertiesof the doped systems of ZnTe:TM, CdTe:TM and MnTe:TM.We find that the Mnantiferromagnetic (AFM) background significantly decreases the clustering trend of doped TMimpurities except Ni, and also effectively enhances the magnetic couplings between Fe, Co andNi impurities. Both the degrading of clustering trend and the enhancement of magnetic couplingare expectedfor MnTe doped with Fe, indicating that the host AFM background may bebeneficial to semiconductor materials ofhigh Currie Temperature (TC).Chapter Four mainly introduce the research results of intrinsic defects-related properties ofwurtzite CoO and MnO. For wurtzite MnO system, we find that the p/n conductivity could betuned through adjusting the oxygen partial pressure of the growth condition. O-rich conditioncorresponds to p-type conductivity with the mainly formed defects of Oi, Oi+OMn, OMnand VMn,while O-poor condition corresponds to n-type conducting with the dominate defects of VO, MnO,Mniand VO+Mni. For wurtzite CoO system, it is very easy to be designed as p-typesemiconductor, but hardfor the n-type one.We expect that the tunable p/n conductivity ofwurtzite MnO could brings more application prospects for wurtzite semiconductors.Chapter Five will concisely introduce my on-going and planned researches.The summary of this dissertation is arranged at the end, with the related references and theachievements during the Ph.D candidate period.更多还原