Optically pumped lasing at 300.4 nm in AlGaN MQW structures grown by plasma-assisted molecular beam epitaxy on c-Al2O3

We have demonstrated optically pumped room‐temperature pulse lasing at 300.4 nm from an AlGaN‐based multiple‐quantum‐well (MQW) structure grown by plasma‐assisted molecular beam epitaxy on a c‐sapphire substrate. The lasing was achieved at the threshold peak power of ∼12 MW/cm2. The MQW structure involved AlGaN/AlN short‐period superlattices to decrease the threading dislocation densities from 1011 down to 109–1010 cm−2. Studies of time‐resolved photoluminescence (TRPL) spectra and cw PL temperature dependences (10–300 K) of different MQW structures, as well as numerical calculations of the optical gain and confinement in the laser structure allowed us to conclude about the optimum design of AlGaN‐based MQW structures for the lower threshold UV lasing.