Deep ultraviolet photopumped stimulated emission from partially relaxed AlGaN multiple quantum well heterostructures grown on sapphire substrates

A low threshold optical power density of 240 kW/cm2 is achieved for room temperature stimulated emission at 276 nm in AlGaN/AlGaN multiple quantum well (MQW) structures over AlN/sapphire templates. The heterostructures were grown by low-pressure metalorganic chemical vapor deposition whereas a pulsed ArF excimer laser (λexc = 193 nm) was used as the pumping source for photoluminescence measurements in edge configuration. The light emitted from the MQWs above threshold exhibits a minimum linewidth of 1.2 nm and is dominated by transverse electric polarization above threshold. The optical confinement factor in the active region was calculated to be about 2%.