AlGaN-based deep UV (DUV) LEDs generally employ a p-type electron blocking layer (EBL) to suppress electron overflow. However, Al-rich III-nitride EBL can result in challenging p-doping and large valence band barrier for hole injection as well as epitaxial complexity. As a result, wall plug efficiency (WPE) can be compromised. Our systematic studies of band diagram and carrier concentration reveal that carrier concentrations in the quantum well and electron overflow can be significantly impacted because of the slope variation of the quantum barrier (QB) conduction and valence bands, which in turn influence radiative recombination and optical output power. Remarkably, grading the Al composition from 0.60 to 0.70 for the 12-nm-thick AlGaN QB of the DUV LED without the EBL can lead to 13.5% higher output power and similar level of overflown electron concentration (~1 × 1015/cm3) as opposed to the conventional DUV LED with the p-type EBL. This paradigm is significant for the pursuit of higher WPE or shorter emission wavelength for DUV LEDs and lasers, as it provides a new direction for addressing electron overflow and hole injection issues.
|Original language||English (US)|
|Number of pages||11|
|Journal||IEEE Photonics Journal|
|State||Published - Apr 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): BAS/1/1664-01-01||URF/1/3437-01-01||REP/1/3189-01-01||OSR-2017-CRG6-3437.02
Acknowledgements: The work of Z. Ren, Y. Lu, H.-H. Yao, H. Sun, C.-H. Liao, and X. Li was supported in part by King Abdullah University of Science and
Technology (KAUST) Baseline BAS/1/1664-01-01, KAUST CRG URF/1/3437-01-01, GCC REP/1/3189-01-01; and in part by the National Natural Science Foundation of China under Grant 61774065. The work of Y. Lu, J. Yan, J. Wang, and J. Li was supported by the National Key R&D Program of China under Grants 2016YFB0400803 and 2016YFB0400802. The work of J. Dai and C. Chen was supported in part by the Key Project of Chinese National Development Programs under Grant 2018YFB0406602 and in part by the National Natural Science Foundation of China under Grant 61774065. The work of J.-H. Ryou was supported in part by KAUST under Contract OSR-2017-CRG6-3437.02 and in part by the Texas Center for Superconductivity at the University of Houston.