Walde SHuang C.-YTsai C.-LHsieh W.-HFu Y.-KHagedorn SYen H.-WLu T.-CWeyers MHuang C.-Y.HUNG-WEI YEN2022-03-222022-03-22202213596454https://www.scopus.com/inward/record.uri?eid=2-s2.0-85122631360&doi=10.1016%2fj.actamat.2022.117625&partnerID=40&md5=8ca2013467f0e4467eb7d4708aefedd0https://scholars.lib.ntu.edu.tw/handle/123456789/598387AlGaN-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 (<65%), decent thickness (>1.5 ?m), and a low TDD (<1.0 × 109 cm?2) simultaneously becomes possible. Additionally, the idea of an optimal edge TDD (ρe,opt) in the AlN buffer was revealed for growing high-quality n-AlGaN layers with a targeted thickness. After a deliberate strain-TDD engineering for Si:AlN and n-AlGaN, high-power UVC LEDs (λ = 275 nm, P > 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. ? 2022 Acta Materialia Inc.Aluminum gallium nitrideAluminum nitrideEdge dislocationsElectric resistanceInterface statesLattice constantsLight emitting diodesSemiconductor alloysStrainCurrent spreadingForward voltageHigh powerHigh qualityIn-plane latticesIn-plane strainsLightemitting dioden-AlGaNStrain stateThreading dislocation densitiesIII-V semiconductorsjournal article10.1016/j.actamat.2022.1176252-s2.0-85122631360