We report the results of two studies of the growth and physical properties of AlGaN-based short-period superlattices (SPSLs), each aimed at improving light emission. In the first experiment, we grow structures on bulk AlN substrates. We observe ∼ 3 times higher luminescence efficiency than identically grown structures on sapphire. In the second experiment, we grow structures on sapphire while controlling the growth mode. We observe a significant improvement in the room temperature cathodoluminescence efficiency (at least by factor of 10) of AlGaN quantum wells when the 3D growth mode is induced by reduced flux of ammonia over identically prepared structures grown in the 2D mode.