Enhanced room-temperature mid-ultraviolet emission from AlGaN/AlN Stranski-Krastanov quantum dots

We report on the identification of an optimum deposited amount of AlGaN in AlGaN/AlN quantum dot (QD) superlattices grown by molecular-beam epitaxy, which grants maximum luminescence at room temperature by finding a compromise between the designs providing maximum internal quantum efficiency (60%) and maximum QD density (9.0 × 1011 cm−2). The average Al composition in the QDs is estimated at 10.6% ± 0.8% by combining x-ray diffraction measurements with three-dimensional calculations of the strain distribution. The effect of the variation of the QD height/base-diameter ratio on the interband and intraband optical properties was explored by fitting the experimental data with three-dimensional calculations of the band diagram and quantum confined states.