Sub-230 nm deep-UV emission from GaN quantum disks in AlN grown by a modified Stranski–Krastanov mode

We report tunable deep-ultraviolet (DUV) emission over the 222–231 nm range from 1–2 monolayer (ML) GaN quantum disks (QDs) grown in an AlN matrix. The linewidth of the emission were as narrow as ∼10 nm at 5 K. The disks were grown in modified Stranski–Krastanov (mSK) mode. High resolution scanning transmission electron microscopy (STEM) images confirmed insertion of 1–2 MLs of GaN between 3 nm AlN barriers. The internal quantum efficiency was estimated from low temperature photoluminescence measurements for the disks, and compared with 1 and 2 ML GaN quantum wells/AlN barriers. The internal quantum efficiency (IQE) of the GaN QDs was found to be ∼35% for 222 nm emission, ∼200% higher than 1 ML GaN QWs.