深紫外AlGaN光学各向异性与自旋轨道调制研究

Since the emergence of AlGaN, it is considered to be a promising material for ultraviolet optoelectronic devices in the field of information storage, air and water purification, biomedical applications, due to its excellent properties. However, the AlGaN optoelectronic devices with high efficiency are still challenging and suffer from the efficiency droop while the wavelength is decreased attributed to the opposite optical anisotropy between Ga-rich AlGaN and Al-rich AlGaN. In order to under the underlying mechanism on atomic scale, the optical anisotropy of the AlGaN is required to be systematically studied in terms of spin-polarized electrons. Based on the first principle simulation, the band engineering of the quantum structure can be performed by the composition, well and barrier thickness. The coupling among the polarization, spin orbits, quantum states and the light field is investigated by calculating the band structure, charge density and the dielectric function. The feasibility of the optical anisotropy modification and the electric-optic enhancement is explored by combining the polarization field, spin-polarized electrons and external electric field.

AlGaN宽禁带半导体材料具有带隙可调范围广，物理和化学性能稳定等特点，在信息存储、生物医学、信息探测、普通照明等领域的应用具有广泛的应用前景。然而，高Al组分AlGaN晶体结构和光学各向异性独特，制约了材料制备与光电应用的发展。本项目从微观原子层面理解各向异性与AlGaN体系中自旋极化电子的内在联系。借助第一性原理模拟设计，不同组分、不同阱宽和垒厚的AlGaN量子结构，通过计算其能带结构、电荷分布以及光学介电响应函数，揭示AlGaN极化场、自旋轨道、量子态和光场之间的相互耦合和作用机制，利用极化场、自旋极化和外电场协同作用调控偏振光传播，实现深紫外AlGaN光学各向异性的改性，进一步增强AlGaN光折变电光效应。

本项目研究工作基本按照研究计划执行，采用理论和实验相结合的方法，围绕深紫外AlGaN光学各向异性与自旋轨道调制研究，首先开展了AlxGa1-xN量子结构调控偏振光发射及传播特性研究，模拟不同组分AlGaN材料的能带结构和介电函数色散曲线，探明自旋轨道参与偏振光发射、传播、吸收过程的机理。设计Mg掺杂调控高Al组分AlGaN量子结构光偏振特性，调控带边辐射由TM偏振光辐射转变为TE偏振光辐射，提升高Al组分c面AlGaN发光器件的正面出光。二维异质结构吸附体系自旋极化的形成和转变机制，为后续强极化效应下具有高度局域化的二维电子气的AlxGa1-xN/GaN异质结构体系构建及其自旋电子性质表征调控提供有益的理论指导。理论设计超短周期AlN/GaN超晶格结构，通过实验制备基于超短周期AlN/GaN超晶格MSM光电探测器实现了预期的窄带吸收特性。设计原位测试LED应力的拉曼测试系统，揭示应变极化AlGaN量子结构的能带特征和功能调控规律，提出应变和极化特性的合理利用思路。设计共振增强的GaN/AlGaN量子阱电光效应材料，实现AlGaN结构非线性光学特性调控。相关研究成果为Al新型量子结构调控器件的设计提供材料和物理基础。