Author:
Khan M. Ajmal,Maeda Noritoshi,Yun Joosun,Jo Masafumi,Yamada Yoichi,Hirayama Hideki
Abstract
AbstractCrystal growth of eco-friendly, ultrawide bandgap aluminium gallium nitride (AlGaN) semiconductor-based ultraviolet-B (UVB) light-emitting diodes (LEDs) hold the potential to replace toxic mercury-based ultraviolet lamps. One of the major drawbacks in the utilisation of AlGaN-based UVB LEDs is their low efficiency of about 6.5%. The study investigates the influence of Al-graded p-type multi-quantum-barrier electron-blocking-layer (Al-grad p-MQB EBL) and Al-graded p-AlGaN hole source layer (HSL) on the generation and injection of 3D holes in the active region. Using the new UVB LED design, a significant improvement in the experimental efficiency and light output power of about 8.2% and 36 mW is noticed. This is accomplished by the transparent nature of Al-graded Mg-doped p-AlGaN HSL for 3D holes generation and p-MQB EBL structure for holes transport toward multi-quantum-wells via intra-band tunnelling. Based on both the numerical and experimental studies, the influence of sub-nanometre scale Ni film deposited underneath the 200 nm-thick Al-film p-electrode on the optical reflectance in UVB LED is investigated. A remarkable improvement in the efficiency of up to 9.6% and light output power of 40 mW, even in the absence of standard package, flip-chip, and resin-like lenses, is achieved on bare-wafer under continuous-wave operation at room temperature. The enhanced performance is attributed to the use of Al-graded p-MQB EBL coupled with softly polarised p-AlGaN HSL and the highly reflective 0.4 nm-thick Ni and 200 nm-thick Al p-electrode in the UVB LED. This research study provides a new avenue to improve the performance of high-power p-AlGaN-based UVB LEDs and other optoelectronic devices in III–V semiconductors.
Funder
New Energy and Industrial Technology Development Organization
Publisher
Springer Science and Business Media LLC
Reference51 articles.
1. Access on 24 Sep. 2019 http://www.mercuryconvention.org/
2. Access on 06 Dec 2020, Available from: https://sdgs.un.org/goals
3. Torii, K. & Morita, A. UVB irradiation induces HMGB1 expression in keratinocytes without promoting apoptosis. Exp. Dermatol. 25, 741–742. https://doi.org/10.1111/exd.13047,27094746 (2016).
4. Kneissl, M. & Rass, J., eds. III-Nitride Ultraviolet Emitters Technology and Applications, Springer Series in Material Science (Springer, 2016). 227, Ch. 1
5. James et al. Clinical dermatology. Saunders Elsevier. p-335. ISBN 0-7216-2921-0 (2006)
Cited by
37 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献