High-quality AlGaN epitaxy on lattice-engineerable AlN template for high-power UVC light-emitting diodes

• Published in: Acta materialia 2022-03, Vol.226, p.117625, Article 117625
• Main Authors: Walde, Sebastian, Huang, Cheng-Yao, Tsai, Chia-Lung, Hsieh, Wen-Hsuang, Fu, Yi-Keng, Hagedorn, Sylvia, Yen, Hung-Wei, Lu, Tien-Chang, Weyers, Markus, Huang, Chia-Yen
• Format: Article
• Language: English
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2022.117625

AlGaN-based UVC light-emitting diodes (LED) were fabricated on high-quality AlN templates with an engineerable in-plane lattice constant. The controllability of the in-plane strain originated from the vacancy formation in Si-doped AlN (AlN:Si) and their interaction with edge dislocations. The strain state of the Si:AlN top interface could be well depicted by a dislocation-tilt model depending on the buffer strain state, threading dislocation density (TDD), and regrown Si:AlN thickness. The validity of the model was verified by cross-sectional TEM analysis. With a gradually widened lattice constant of regrown Si:AlN layer, strain-induced defects of subsequently grown n-AlGaN was suppressed. Therefore, growing a current spreading layer which possesses a moderate Al content (1.5 µm), and a low TDD ( 200 mW) with a low forward voltage (Vf = 5.7 volt) were demonstrated at I = 1.35 A. The low forward voltage under high current injection density was attributed to the success in preparation of a low series resistance and high-quality n-AlGaN current spreading layer. [Display omitted]