Uneven AlGaN multiple quantum well for deep-ultraviolet LEDs grown on macrosteps and impact on electroluminescence spectral output

AlGaN-based LEDs (lambda < 300 nm) fabricated on n-AlGaN templates with a threading dislocation density larger than 5x10(8)/cm(2), which were grown on (0001) sapphire with a 1.0 degrees miscut relative to the m-plane, showed external quantum efficiencies (EQEs) of 3.5, 3.9, 6.1, and 6.0% at 266, 271, 283, and 298 nm, respectively. These EQE values reveal significantly high internal quantum efficiencies (IQEs). This performance was obtained using an uneven multiple quantum well (MQW) grown on the n-AlGaN template with macrosteps having height larger than the well thickness. The electroluminescence spectra of the fabricated LEDs using this MQW structure shifts to a longer wavelength compared with those on sapphire with a miscut angle of 0.3 degrees relative to the m-plane. Furthermore, the LEDs with this MQW show no deleterious effect on the lifetime, broader electroluminescence spectral widths, and higher output powers when using sapphire with a miscut of 1.0 degrees. (C) 2017 The Japan Society of Applied Physics