锗烯和锗量子点的能隙调控密度泛函研究

发布时间：2018-03-26 13:59

本文选题：锗烯　切入点：锗量子点　出处：《浙江大学》2017年硕士论文

【摘要】：当前窄禁带半导体材料中,晶体锗由于具备良好的微电子兼容性而被寄予厚望。锗材料比硅材料的波尔激子半径更大,具有更加显著的表面效应和量子限域效应等,因而锗材料在半导体器件的应用上如集成电路、太阳电池、生物材料等更易获得优异的性能。近几年,低维(二维、一维、零维)锗材料的研究受到广泛的关注,并取得了突破性的进展,如锗烯(二维锗材料)成功地在铂、金衬底上合成,有力的促进了锗烯在各个领域的应用。锗烯结构与石墨烯相似,其带隙约为0eV,所以锗烯的器件化应用需要将其带隙打开。研究者们已经采用湿化学的方法合成了氢钝化的锗烯,其带隙是3.6 eV,并且是直接带隙,比硅烯(间接带隙,4eV)具有更有大的研究前景。通过表面改性调控能带,锗烯比硅烯更有潜力成为一种重要的应用于光电子领域的半导体材料。现阶段的相关研究还停留在对其尺寸效应对性能的影响,而掺杂研究非常少,并且极度缺乏理论的指导。因此通过密度泛函理论探索掺杂对锗量子点的几何结构和电子性能也亟待研究。本文研究了表面改性(氢化锗烷化、烷氧基化、胺化及苯基化)对氢钝化锗烯电子结构的影响以及硼、磷掺杂对锗量子点电子结构的调控作用和形成机制。主要取得以下结论:(1)氢化锗烷化、烷氧基化、胺化及苯基化对氢钝化锗烯几何结构的影响非常小。表面改性会增大氢钝化锗烯的禁带宽度,尤其对烷基化和胺基化的锗烯禁带宽度影响较大。胺化和苯基化会使氢钝化锗烯由直接禁带半导体变为间接禁带半导体;而氢化锗烷化和烷氧基化并不会改变其直接禁带半导体的特征。(2)硼掺杂锗量子点的形成能随着硼在锗量子点的中心位置向表面移动而逐渐降低,即硼原子最容易掺杂到锗量子点的表面。当硼掺杂在锗量子点内部时,在价带上方引入了深杂质能级,当硼掺杂到锗量子点的表面时,在接近锗量子点的禁带中间的位置引入了深能级。磷掺杂锗量子点的与硼的变化规律相似,但形成能比硼掺杂锗量子点偏高,因此硼原子比磷原子更容易掺入到锗量子点中。(3)对于硼磷共掺的锗量子点,其形成能均小于硼原子和磷原子单掺的锗量子点。而其电子结构中均在价带上方引入了深能级。硼磷共掺使锗量子点带隙变化最大的为0.37 eV,接近硼磷共掺硅量子点带隙变化的两倍(0.2 eV),因此硼磷共掺的锗量子点电子结构比硅量子点更具有可调控性。
[Abstract]:In current narrow band semiconductor materials, crystal germanium is expected to have good microelectronic compatibility. Germanium material has a larger Bolt exciton radius than silicon material, and has more obvious surface effect and quantum limiting effect, etc. Therefore, the application of germanium in semiconductor devices such as integrated circuits, solar cells, biomaterials, etc. In recent years, the research of low-dimensional (two-dimensional, one-dimensional, zero-dimensional) germanium materials has received extensive attention. Breakthrough progress has been made, such as the successful synthesis of germane (two-dimensional germanium) on platinum and gold substrates, which promotes the application of germane in various fields. The structure of germane is similar to that of graphene. The band gap of germanium is about 0 EV, so it is necessary to open the band gap for the device of germane. The researchers have synthesized hydrogen passivated germane by wet chemical method. The band gap is 3.6 EV and is a direct band gap. It is more promising than silyene (indirect band gap 4eV). Germane has more potential than silicene to become an important semiconductor material in the field of optoelectronics. Therefore, it is urgent to study the geometric structure and electronic properties of doped germanium quantum dots by density functional theory. In this paper, the surface modification (hydrogenation of germanium, alkoxylation of germanium, alkoxylation of germanium) is studied. The effects of amination and phenylation on the electronic structure of hydrogen passivated germanium and the effect of boron and phosphorus doping on the electronic structure of germanium quantum dots were studied. The main conclusions are as follows: 1) hydrogenated germanium alkylation, alkoxylation, The effect of amination and phenylation on the geometric structure of hydrogen passivated germanium is very small. The surface modification will increase the band gap of hydrogen passivated germanium. In particular, the band gap of alkylation and amination germane is greatly affected. Amination and phenylation can change the hydrogen passivated germanium from direct band gap semiconductor to indirect band gap semiconductor. However, the formation energy of boron doped germanium quantum dots decreases with the center position of boron moving toward the surface, but the alkylation and alkoxylation of germanium do not change the characteristics of the direct band gap semiconductor. The formation energy of boron doped germanium quantum dots decreases with the center position of germanium quantum dots moving to the surface. That is, boron atoms are most easily doped to the surface of germanium quantum dots. When boron is doped inside germanium quantum dots, deep impurity levels are introduced above the valence band, and when boron is doped into the surface of germanium quantum dots, Deep energy levels are introduced near the gap between the band gaps of the germanium quantum dots. The variation law of the phosphorus-doped germanium quantum dots is similar to that of boron, but the formation energy is higher than that of boron-doped germanium quantum dots. Therefore, boron atoms are more easily adulterated into germanium quantum dots than phosphorus atoms) for boron-phosphorus co-doped germanium quantum dots. The formation energy of GE quantum dots is smaller than that of boron atoms and phosphorus atoms, and deep energy levels are introduced above the valence band in the electronic structure. Boron and phosphorus co-doped germanium quantum dots with the largest band gap change is 0.37 EV, which is close to boron phosphorus co-doped silicon quantum. The change of band-gap is about 0.2 EV, so the electronic structure of boron-phosphorus co-doped germanium quantum dots is more controllable than that of silicon quantum dots.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;O641.1

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