Optically-pumped 285 nm edge stimulated emission from AlGaN-based LED structures grown by MOCVD on sapphire substrates

285 nm stimulated emission (SE) is demonstrated at room temperature from optically-pumped AlGaN multiple quantum wells (MQWs) deposited between a Si-doped AlGaN current spreading layer and a 25 nm Mg-doped p-type AlGaN clad layer. The epitaxial structures were grown by low pressure metalorganic chemical vapor deposition (MOCVD) on high-quality AlN/sapphire templates and a pulsed ArF excimer laser was used as the excitation source for lasing experiments. The threshold power density (Pth) was measured to be 970 kW/cm2 and the SE was strongly polarized in transverse electric (TE) mode. The minimum emission linewidth was ?2 nm. The high value of Pth is primarily attributed to optical losses due to pump laser absorption in the top p-AlGaN. Our results show the viability of the MOCVD growth technology in conjunction with c-plane sapphire substrates to develop electrically-pumped deep-UV laser diodes.