高Al组分AlGaN应变量子结构制备与特性研究

AlGaN based quantum structure materials are very promising materials for the applications in short wavelength of optoelectronic devices (both emitters and detectors) and high power/temperature electronic devices. However, due to the high strained and strong polarization field, the high-composition AlGaN based quantum structures have unique geometric structures, electronic structures, and selection rule of quantum transitions. And they are still lag behind. In this proposal, we will focus on fabrication and characteristic of strained AlGaN quantum structures with high Al content. To understand the strain effects within the AlGaN quantum structures, comprehensive theoretical simulations will be performed by the first-principles firstly. Based on the simulation results, novel strained quantum structures will be designed to modify the strained effect and energy band structure. Accordingly, growth kinetic processes of strain modified quantum structures will be studied by metalorganic chemical vapor deposition method (MOCVD). After growth, the quality of interface, strained field of the AlGaN quantum structures will be analyzed by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The optical properties will be investigated by photoluminescence, cathodoluminescence, and ellipsometry spectra. To get a deeper insight into the recombination dynamics and assess the internal quantum efficiency, the temperature-dependent time-resolved photoluminescence measurements will also be performed. Based on the measurement results, optimization of strained structure will be carried out to improve the ability of quantum confinement. Finally, high internal-quantum-efficiency AlGaN based quantum structure materials will be achieved.

高Al组分AlGaN低维量子结构为大失配应变、强极性体系，具有复杂、特殊的几何结构、电子结构以及量子跃迁的选择规律。了解应变、极化场与其能带、量子能级的内在关联，掌握其调控规律，不仅对于丰富和发展宽禁带半导体物理学具有重要的意义，还将为Ⅲ族氮化物半导体在短波长光电子器件的应用奠定科学基础。本项目将结合第一性原理计算和MOCVD外延生长方法，从理论模拟设计、实验外延生长和特性表征方面，开展高Al组分AlGaN低维应变量子结构制备及其特性研究。在掌握应变和极化场的调控规律的基础上，通过能带工程，设计新型应变量子结构，以期达到应变、极化、能带结构的调控；探索在非平衡条件下，高Al组分AlGaN应变量子结构的外延生长技术；深入研究应变、极化场与其能带、量子跃迁选择规律、光学性质的内在关联；在此基础上，优化应变量子结构，以提高载流子量子限制能力，最终获得高电子空穴复合效率的量子结构。

高Al组分AlGaN低维量子结构为大失配应变、强极性体系，具有复杂、特殊的几何结构、电子结构以及量子跃迁的选择规律。了解应变、极化场与其能带、量子能级的内在关联，掌握其调控规律，将为Ⅲ族氮化物半导体在短波长光电子器件的应用奠定科学基础。本项目结合第一性原理计算和MOVPE外延生长方法，从理论模拟设计、实验外延生长和特性表征方面，开展高Al组分AlGaN低维应变量子结构制备及其特性研究，并初步开展了所设计的量子结构在紫外光电器件方面的应用研究。获得主要成果有1）基于第一性原理计算方法探索了掺杂对量子阱结构的极化场、能带结构、载流子分离的影响；通过MOVPE外延，引进In作为表面活性剂，并设计和研究了生长中断技术对界面质量的影响，获得了表面平整、界面陡峭的高Al组分AlGaN量子阱结构材料。2）采用第一性原理计算分析了GaN/AlN异质结量子点结构中的应力、极化场、电子结构等，进而通过MOVPE自组织生长了发光波长位于308nm、半高宽窄、内量子效率高达62%的GaN/AlN量子点结构；并以此结构制备了具有良好的发光波长热稳定性的量子点紫外LED。3）采用第一性原理模拟设计二维AlGaN量子结构，深入分析其电子结构和光吸收性质；并结合带边激子跃迁行为，从理论上预测了超短周期AlN/GaN超晶格结构的固有吸收窄带、可调控深紫外波长及电子隧穿输运特性，并以此结构设计并备了MSM深紫外光电探测器，器件表现出明显的窄带特征，半高宽最窄可达210 meV。