We explore the effect of the subwell centers and related carrier dynamics mechanisms in dislocation-free DUV AlGaN/AlGaN multiple quantum wells (MQWs) homoepitaxially grown on an AlN substrate. Cross-sectional imaging and energy-dispersive X-ray compositional analyses using scanning transmission electron microscopy (STEM) reveal epitaxial layers of very high crystalline quality, as well as ultrathin Al-rich subquantum barrier and subwell layers at the interface between the wells and the barriers. Carrier dynamic analyses studied by power- and temperature-dependent time-resolved and time-integrated photoluminescence (PL) and PL excitation measurements, as well as numerical simulations, reveal the carrier repopulation mechanisms between the MQWs and subwell sites. This advanced analysis shows that the subwell/sub-barrier structure results in additional exciton localization centers, enhancing the internal quantum efficiency via staggered carrier repopulation into the MQWs to reach a maximum of ∼83% internal quantum efficiency, which remains high at high injected carrier densities in the droop region. Both experimental and numerical simulation results show that the slight efficiency droop can be due to Auger recombination, counteracted by a simultaneous increase in radiative recombination processes at high power density, demonstrating the role of the subwells/sub-barriers in efficiency enhancement.

中文翻译：

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亚量子阱对高效DUV无位错AlGaN / AlGaN基多量子阱中载流子动力学的影响

我们探索在AlN衬底上同质外延生长的无位错DUV AlGaN / AlGaN多量子阱（MQWs）中子阱中心和相关载流子动力学机制的影响。使用扫描透射电子显微镜（STEM）进行的横截面成像和能量色散X射线成分分析显示，晶体质量非常高的外延层，以及在孔与孔之间的界面处的超薄富Al亚量子势垒和亚阱层。障碍。通过与功率和温度相关的时间分辨和时间积分的光致发光（PL）和PL激发测量研究的载流子动力学分析以及数值模拟研究，揭示了MQW和子阱位点之间的载流子再填充机制。这项先进的分析表明，子阱/子势垒结构导致了其他激子定位中心，通过将载流子交错填充到MQW中来提高内部量子效率，以达到最大〜83％的内部量子效率，在高注入载流子上仍然很高下垂区域的密度。实验和数值模拟结果均表明，效率的小幅下降可能归因于俄歇复合，而高功率密度下辐射复合过程的同时增加抵消了俄歇复合，从而证明了子阱/子势垒在效率增强中的作用。在下垂区域中的高注入载流子密度下，它仍然很高。实验和数值模拟结果均表明，效率的小幅下降可能归因于俄歇复合，而高功率密度下辐射复合过程的同时增加抵消了俄歇复合，从而证明了子阱/子势垒在效率增强中的作用。在下垂区域中的高注入载流子密度下，它仍然很高。实验和数值模拟结果均表明，轻微的效率下降可能是由于俄歇复合引起的，在高功率密度下辐射复合过程的同时增加抵消了俄歇复合的存在，证明了子阱/子势垒在效率增强中的作用。