精密加工优化AlGaN深紫外LED量子阱应变以及偏振特性的研究

Deep ultraviolet (UV) light emitting diodes (LED) with wavelength shorter than 300 nm have attracted enormous attention owing to their applications in sterilization, medical technology, photolithography, biomedical sensing, high density optical data storage and covert communication. AIGaN is one of the most promising III-nitride materials for applications in deep UV range. In addition to being environmentally safe, LED-based solid state deep UV sources provide considerable advantages in size, power consumption, and spectral control over traditional UV light sources. Although the great progress has been made to improve internal quantum efficiency, the external quantum efficiency is still low due to very poor light extraction efficiency. For AlGaN based LED grown on c-plane sapphire substrate, light cannot be extracted easily since the dominant emission is from the photons with polarization parallel to the c-axis [transverse magnetic (TM) polarization]. Utilizing ultra precision machining, this study will focus on optimizing strain in quantum wells to improve transverse electric (TE) polarization, which will improve light extraction efficiency. In this study, we will build a model to simulate the strain/stress field in multiple quantum wells and find its relation to substrate strain. After devices are processed by ultra precision machining, the strain/stress condition, light polarization and efficiency will be measured and compared with the theoretical model. In the mean while, we will monitor the roughness, structure degradation and defect density to eliminate the other factors which might also affect the light extraction efficiency. Upon completion of this study, we will have a more accurate strain/stress model in AlGaN based deep UV quantum wells with relation to substrate strain. This model will be used to improve future material growth and device design. We will also build the relationship of strain in quantum wells, light polarization and extraction efficiency and find a new method to improve light extraction efficiency.

AlGaN基深紫外LED具有体积小，能耗低，无污染的特点，在杀菌、医疗、光刻、生化检测、高密度的信息储存和保密通讯等领域具有重大应用价值，然而如何提高发光效率仍然是急需解决的关键技术难题。在蓝宝石衬底上生长的AlGaN基深紫外LED，随着Al组分增加及波长变短，量子阱内应变会逐渐增强，所发出的光会逐渐从横电波(TE)向横磁波(TM)偏转，出光效率随之降低。本项目致力于研究用超精密加工的方法优化AlGaN基深紫外LED量子阱内应变，从而调整光偏振特性，最终达到提高LED器件出光效率的目的。本项目从建立量子阱内应变场模型出发，研究通过两种超精密加工的方法改变衬底应变的方式优化量子阱内应变，建立其对偏振特性以及出光效率的模型并研究其改变机制。本项目工作处于国际前沿，具有重要的理论意义和实际应用价值。

AlGaN基深紫外LED具有体积小，能耗低，无污染的特点，在杀菌、医疗、光刻、生化检测、高密度的信息储存和保密通讯等领域具有重大应用价值，然而如何提高发光效率仍然是急需解决的关键技术难题。在蓝宝石衬底上生长的AlGaN基深紫外LED，随着Al组分增加及波长变短，量子阱内应变会逐渐增强，所发出的光会逐渐从横电波(TE)向横磁波(TM)偏转，出光效率随之降低。本项目致力于研究用超精密加工的方法优化AlGaN基深紫外LED量子阱内应变，从而调整光偏振特性，最终达到提高LED器件出光效率的目的。本项目从建立量子阱内应变场模型出发，研究通过两种超精密加工的方法改变衬底应变的方式优化量子阱内应变，建立其对偏振特性以及出光效率的模型并研究其改变机制。本项目工作处于国际前沿，具有重要的理论意义和实际应用价值。.本项目在研究周期内，针对AlGaN基深紫外LED发光效率低的问题，按计划完成了项目的研究内容。本项目研究了深紫外LED量子阱模型，基于理论仿真与实验相结合研究了深紫外LED量子阱应变结构和组分对器件发光性能的影响规律，研究应变对芯片电学接触性能的影响，并通过实验测试分析了深紫外LED的外延和芯片工艺对器件性能及可靠性的影响。本项目通过优化研究深紫外LED量子阱结构，揭示应变对深紫外LED芯片电学性能的影响机制，以及研究缺陷对外延和芯片性能的影响规律，为蓝宝石衬底外延AlGaN基深紫外LED器件量子阱模型提供理论基础和实验指导。