氮化铟基半导体异质生长和掺杂的数值模拟研究

Indium nitride (InN) is a promising material for near-infrared optoelectronics, high-efficiency solar cells, and high-speed electronics owing to its considerably narrower direct band gap (0.7–0.8 eV) and superior electron transport characteristics compared to AlN and GaN. As the growth of good quality InN single crystals is difficult, this material is usually observed by the hetero-epitaxial growth. InN is usually grown using highly reactive nitrogen sources such as NH3 or N2 plasma, which cause nitridation of the substrate surfaces just before the epitaxial growth. This limits the substrates for the epitaxial growth of InN to chemically stable materials. The suitable substrate materials play an important role for the high-quality epitaxial growth. Development of semiconductor growth techniques on perovskite oxides substrates allows us to fabricate integrated devices which combine the unique properties of superconductors with the conventional semiconductor optical and electronic devices. The fabrication of p- and n-type doped layers underlies the design of virtually all electronic and optoelectronic devices. However, p-type doping in InN has been very difficult to achieve due to its propensity for n-type carrier formation. The knowledge of the InN-based diluted magnetic semiconductors is of great importance for the development of spin-electronic devices, but it is not attracting a lot of attention. We will study the Fourier spectral method for the coupled Schrödinger-Poisson equations, the p-type doped/magnetically doped InN and the microstructure and electrical properties of InN/Sr(Ba,Pb)TiO3 interfaces which include the stable structure and effects of the Column-ⅡA/B and the magnetic dopants on a InN bulk and surface and the adsorption and heterointerface of InN on Sr(Ba,Pb)TiO3. Our study may provide a physical basis and physical insights for the growth and design of InN-based optoelectronic devices.

随着半导体氮化铟(InN)材料生长、测试技术的提高和本征能隙认识的突破，InN有望成为长波长半导体光电器件、全彩显示、高效率太阳能电池等的最佳材料。目前InN体单晶材料主要通过异质外延方法制备，然而常用衬底易氮化，从而影响InN薄膜质量。找到合适的衬底，制备出高质量的InN体单晶材料一直是人们关心的问题。良好的p型和n型掺杂材料是实现InN基光电子器件的前提条件，而人们还没有找到合适的表面p型掺杂候选对象。InN基稀磁半导体的研究有助于自旋电子器件的发展，但其磁性掺杂尚未引起广泛关注。本项目将探索谱方法自洽求解薛定谔—泊松方程，最佳p型/磁性掺杂方案和InN/Sr(Ba,Pb)TiO3异质界面微结构与物理性质，包括II族杂质原子/磁性原子在InN体内和不同(非)极化表面掺杂，InN在Sr(Ba,Pb)TiO3衬底上的吸附生长、异质界面微结构等问题，为InN基光电子器件的制备和设计提供依据。

本课题首先研究InN在BaTiO3(111)和PbTiO3(111)表面吸附生长的结构和电子性质。计算了BaTiO3(111)表面结构弛豫和表面能，BaO3终端面表面能比Ti终端面表面能大。BaTiO3(111)表面In吸附原子比N吸附原子稳定。比较出InN/BaTiO3(111)异质界面原子排列中较稳定的In/BaO3界面，并研究了表面Vo缺陷对In/BaO3异质结影响。计算了PbTiO3(111)的不同终端面的表面巨热力势随元素化学势变化关系，表面相图显示PbO3终端面和Ti终端面可共存。PbTiO3(111)表面In吸附原子比N吸附原子稳定。在所研究的InN/PbTiO3(111)异质界面原子排列中，In/PbO3组成界面比较稳定。In/Ti组成界面的InN/PbTiO3(111)异质结中，Mg或Zn替代In原子组成的替位缺陷可导致InN体内和表面出现p型载流子。随后研究了纤锌矿InN(11-20)薄膜在正交结构LiGaO2(001)衬底吸附生长的结构和电子性质。对于LiGaO2 (001)解理的LiGa终端面和O2终端面，In吸附原子比N原子更稳定。随LiGaO2(001)衬底上的N的覆盖度增加将形成N-N二聚物。表面巨热力势计算结果显示完整的LiGaO2(001)的O2终端面比缺陷O2终端面稳定。InN(11-20)‖LiGaO2(001)异质界面原子排列组合中InN/O2 排列稳定。在LiGaO2(001)的O2终端面反位缺陷InN可能充当InN P型掺杂行为的一个潜在来源。最后研究Ge在SrTiO3(001)表面原子结构和其电子性质。获得Ge在干净SrO和TiO2终端面生长的稳定位，并计算了电子性质。同时考虑了Ge在缺陷表面生长，检查了本征点缺陷巨热力势并做出了相图。比较分析了理想和缺陷条件下异质结构的电子性质。此外，我们还研究SrTiO3(111)极化表面的结构和电子性质。解释了STO(111)表面存在二维电子气的现象。申请人访学期间研究了Ge/SrHfO3、Ge/SrZrO3、GaAs/BaTiO3和GaAs/SrHfO3异质结构表面和界面的结构和电子性质，提出半导体/绝缘氧化物异质界面可以存在二维电子气。