The development of semiconductors is always accompanied by the progress in controllable doping techniques. Taking AlGaN-based ultraviolet (UV) emitters as an example, despite a peak wall-plug efficiency of 15.3% at the wavelength of 275 nm, there is still a huge gap in comparison with GaN-based visible light-emitting diodes (LEDs), mainly attributed to the inefficient doping of AlGaN with increase of the Al composition. First, p-doping of Al-rich AlGaN is a long-standing challenge and the low hole concentration seriously restricts the carrier injection efficiency. Although p-GaN cladding layers are widely adopted as a compromise, the high injection barrier of holes as well as the inevitable loss of light extraction cannot be neglected. While in terms of n-doping the main issue is the degradation of the electrical property when the Al composition exceeds 80%, resulting in a low electrical efficiency in sub-250 nm UV-LEDs. This review summarizes the recent advances and outlines the major challenges in the efficient doping of Al-rich AlGaN, meanwhile the corresponding approaches pursued to overcome the doping issues are discussed in detail.

Y₃Al₅O₁₂∶Ce³⁺荧光粉是目前白光LED的主要发光材料，但在使用时存在封装树脂因散热不佳而发生老化等问题。本文采用无压烧结制备了Y₂MgAl₄SiO₁₂∶Ce³⁺透明陶瓷荧光体，用于替代荧光粉体和调控发光性能。首先通过化学共沉淀法制备前驱体粉体，经高温煅烧后采用冷等静压成型，最后在马弗炉中1 600 ℃煅烧制得透明荧光陶瓷。研究了Ce³⁺掺杂浓度和样品厚度对材料性能的影响，其中掺杂量为0.5%的样品在800 nm处具有56%的透过率，在450 K下发光强度仍能保持室温强度的84%。与蓝光芯片组装成器件测试表明，荧光陶瓷在蓝光LEDs/LDs的激发下发出白光，其CIE色度坐标分别为（0.307 6，0.332 9）和（0.308 0，0.331 6），光效分别为62.6 lm/W和146.3 lm/W。研究结果表明，YMAS∶Ce荧光陶瓷可应用于白光LEDs/LDs领域。

为提供高品质、智能健康的照明光源，基于三基色LED光源构建了线性调光混合照明系统，并提出一种调光调色的优化方法。混合光源的光色度和光强度分别用色温和明度等级来设定，使得混合照明效果更加符合“人因照明”的需求。在系统的智能优化配光过程中，将色温转化为CIE $ {u}'{v}' $色度坐标，明度转化为亮度，使优化计算更加精确。该系统采用线性调光的方式，既能有效避免混合光源闪烁带来的健康安全问题，配合优化算法又有效解决了线性调光色度漂移大的问题。实验结果表明，在2000 K~8000 K的色温范围内，混合照明系统混合光的色度稳定性保持在1阶CIE $ {u}'{v}' $圆内，在对应色温下的整个光强度调节范围内无可察觉的色差。采用线性调光方式在保持光色度稳定上比脉冲宽度调光方式效果更佳。理论探究和实验结果表明该混光照明系统简易可行，具有较高的实用价值。

240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated. Then, the external quantum efficiency (EQE) and light extraction efficiency (LEE) are systematically investigated by comparing size and edge effects. Here, it is revealed that the peak optical output power increases by 81.83% with the size shrinking from 50.0 to 25.0 μm. Thereinto, the LEE increases by 26.21% and the LEE enhancement mainly comes from the sidewall light extraction. Most notably, transverse-magnetic (TM) mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design. However, when it turns to 12.5 μm sized micro-LEDs, the output power is lower than 25.0 μm sized ones. The underlying mechanism is that even though protected by SiO₂ passivation, the edge effect which leads to current leakage and Shockley-Read-Hall (SRH) recombination deteriorates rapidly with the size further shrinking. Moreover, the ratio of the p-contact area to mesa area is much lower, which deteriorates the p-type current spreading at the mesa edge. These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm, which will pave the way for wide applications of deep ultraviolet (DUV) micro-LEDs.

AlGaN-based light-emitting diodes (LEDs) on offcut substrates enhance radiative emission via forming carrier localization centers in multiple quantum wells (MQWs). This study introduces the carrier transport barrier concept, accessing its impact on the quantum efficiency of LEDs grown on different offcut sapphire substrates. A significantly enhanced internal quantum efficiency (IQE) of 83.1% is obtained from MQWs on the 1° offcut sapphire, almost twice that of the controlled 0.2° offcut sample. Yet, 1° offcut LEDs have higher turn-on voltage and weaker electroluminescence than 0.2° ones. Theoretical calculations demonstrate the existence of a potential barrier on the current path around the step-induced Ga-rich stripes. Ga-rich stripes reduce the turn-on voltage but restrict sufficient driving current, impacting LED performance.

采用溶剂挥发法，在室温条件下生长出掺不同浓度Mn⁴⁺的K₂TiF₆∶Mn⁴⁺红光晶体。样品在紫光区和蓝光区都表现出Mn⁴⁺的特征宽带激发，对应于其⁴A₂ → ⁴T₁和⁴A₂ → ⁴T₂能级跃迁。在蓝光激发下，所有晶体都呈现出一系列窄带红光发射，其中最强发射峰位于631 nm处。在这些晶体中，样品K₂TiF₆∶Mn⁴⁺ （13.18%）表现出最高效的红光发射，其内外量子效率分别高达97.2%和83.3%。值得一提的是，该样品表现出荧光负热猝灭效应，其在120 ℃时的红光发射强度是室温时的1.81倍。所得晶体与Y₃Al₅O₁₂∶Ce³⁺ （YAG∶Ce³⁺）组装的暖白光LED流明效率（LE）高达180.9 lm/W、色温低至3 859 K、显色指数为91.3。与β?SiAlON∶Eu²⁺组装成白光LED器件，LE也达101.5 lm/W，显示色域为NTSC （National Television System Committee）标准值的94%。因此K₂TiF₆∶Mn⁴⁺晶体在白光LED照明及显示领域具有潜在应用前景。

紫外光通信在激光雷达、战术通信、航空航天内部安全通讯和片上集成通信等领域有着重要应用前景。传统的紫外光通信LED光源的调制带宽窄、输出光功率低和制造工艺复杂等缺点限制了它在长距离、高速率通信和片上集成通信领域的广泛应用。实验表明，增加单个器件发光面积可提升光输出功率，但增加的器件电容对带宽提升是不利的，因此紫外光通信LED未来的重要研究方向是提升并优化带宽的同时增加器件的光功率密度。UVC Micro?LED器件有着光提取效率高、时间常数小、载流子寿命短、调制速率快及工作电流密度高等出色性能，因此在通讯领域受到科研界和工业界的广泛青睐。本文总结了紫外LED、特别是UVC Micro?LED的相关研究进展，并重点介绍了它们在光通信及其片上集成互联方面的应用。研究发现，对UVC Micro?LED及其阵列制备与性能提升加强研究，是未来提升自由空间和片上互联紫外通信系统性能的最佳解决方案之一。

深紫外LED可通过物理方式破坏病毒和细菌的结构，从而获得高效消毒的效果。相比于工艺成熟的蓝光LED，如何提高深紫外LED的封装可靠性和出光率仍是关键问题。本文采用基底预热方式微固化封装胶，结合阵列点胶方式将石英玻璃固定在镀铜围坝，制备了半无机封装的深紫外LED。该器件的输出波长为275 nm，半峰宽约为11 nm。对比传统类透明材料封装的器件，石英封装的深紫外LED有更高的出光率。在真空红墨水和氦气漏率实验中，采用本文提出的半无机封装技术的深紫外LED器件表现出高密封性。此外，在加速老化测试中，该封装器件的光衰速率在20%以内。实验结果表明，对比有机封装的深紫外LED器件，在基底预热条件下，采用阵列点胶固定石英玻璃是现阶段提高深紫外LED可靠性的一种封装方法。