Unambiguously Enhanced Ultraviolet Luminescence of AlGaN Wavy Quantum Well Structures Grown on Large Misoriented Sapphire Substrate

Abstract
High-quality epitaxy consisting of Al1−xGaxN/Al1−yGayN multiple quantum wells (MQWs) with sharp interfaces and emitting at ≈280 nm is successfully grown on sapphire with a misorientation angle as large as 4°. 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° 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° 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.

Citation
Sun, H., Mitra, S., Subedi, R. C., Zhang, Y., Guo, W., Ye, J., … Long, S. (2019). Unambiguously Enhanced Ultraviolet Luminescence of AlGaN Wavy Quantum Well Structures Grown on Large Misoriented Sapphire Substrate. Advanced Functional Materials, 1905445. doi:10.1002/adfm.201905445

Acknowledgements
The authors acknowledge the funding support from University of Science and Technology of China (KY2100000081), Chinese Academy of Science Funding, National Natural Science Foundation of China (Grant Nos. 61905236 and 61704176), and King Abdullah University of Science and Technology baseline (KAUST) funding (BAS/1/1614-0101). This work was partially carried out at the University of Science and Technology of China Center for Micro and Nanoscale Research and Fabrication.

Publisher
Wiley

Journal
Advanced Functional Materials

DOI
10.1002/adfm.201905445

Additional Links
https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201905445

Permanent link to this record