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首页> 外文期刊>Advanced Functional Materials >Unambiguously Enhanced Ultraviolet Luminescence of AlGaN Wavy Quantum Well Structures Grown on Large Misoriented Sapphire Substrate
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Unambiguously Enhanced Ultraviolet Luminescence of AlGaN Wavy Quantum Well Structures Grown on Large Misoriented Sapphire Substrate

机译：大型取向不正确的蓝宝石衬底上生长的AlGaN波浪形量子阱结构的无歧义增强紫外发光。

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摘要

High-quality epitaxy consisting of Al1-xGaxN/Al(1-y)GayN multiple quantum wells (MQWs) with sharp interfaces and emitting at approximate to 280 nm is successfully grown on sapphire with a misorientation angle as large as 4 degrees. Wavy MQWs are observed due to step bunching formed at the step edges. A thicker QW width accompanied by a greater accumulation of gallium near the macrostep edge than that on the flat-terrace is observed on 4 degrees misoriented sapphire, leading to the generation of potential minima with respect to their neighboring QWs. Consequently, a significantly enhanced photoluminescence intensity (at least ten times higher), improved internal quantum efficiency (six times higher at low excitation laser power), and a much longer carrier lifetime are achieved. Importantly, the wafer-level output-power of the ultraviolet light emitting diodes on 4 degrees misoriented substrate is nearly increased by 2-3 times. This gain is attributed to the introduction of compositional inhomogeneities in AlGaN alloys induced by gallium accumulation at the step-bunched region thus forming a lateral potential well for carrier localization. The experimental results are further confirmed by a numerical modeling in which a 3D carrier confinement mechanism is proposed. Herein, the compositional modulation in active region arising from the substrate misorientation provides a promising approach in the pursuit of high-efficient ultraviolet emitters.
机译：高质量外延在蓝宝石上成功地生长，其取向角大至4度，该高质量外延由具有清晰界面并发射约280 nm的Al1-xGaxN / Al（1-y）GayN多量子阱（MQW）组成。由于在台阶边缘形成台阶聚束，因此观察到波浪状MQW。在4度错位的蓝宝石上观察到较厚的QW宽度，并且在宏台阶边缘附近的镓积累量大于在平坦平台上的镓积累量，从而导致相对于其相邻QW的潜在最小值产生。因此，实现了显着增强的光致发光强度（至少高十倍），改进的内部量子效率（在低激发激光功率下提高了六倍）以及更长的载流子寿命。重要的是，在4度方向错误的基板上的紫外线发光二极管的晶片级输出功率几乎增加了2-3倍。该增益归因于由于在步分束区域处的镓积累而在AlGaN合金中引入了成分不均匀性，从而形成了用于载流子定位的横向势阱。通过数值模型进一步证实了实验结果，其中提出了3D载波限制机制。在本文中，由于基板取向不良而引起的有源区域中的成分调制为追求高效的紫外线发射器提供了有希望的方法。

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