The authors demonstrated AlGaN multiquantum-well (MQW) deep-ultraviolet light-emitting diodes(LEDs) with wavelengths in the range of 231 – 261 nm , fabricated on low threading dislocation density AlN buffers formed through an ammonia ( N H 3 ) pulse-flow multilayergrowth technique. The authors obtained a single-peaked operation of the AlGaN-MQW LED with a wavelength of 231 nm , which is the shortest wavelength of AlGaN-based LED on sapphire. The maximum output power and external quantum efficiency of the 261 and 231 nm LEDs were 1.65 mW and 0.23% under room-temperature (RT) continuous-wave (cw) operation, and approximately 5 μ W and 0.001% under RT pulsed operation, respectively.

Stimulated emission was observed from optically pumped GaN quantum dots in an AlxGa1−xN separate confinement heterostructure fabricated on 6H-SiC(0001) substrate by metal organic chemical vapor deposition. Nanostructural GaN quantum dots, with an average size of ∼10 nm width, ∼1–2 nm height, and density of ∼1011 cm−2, were self-assembled on the AlxGa1−xN cladding layer surface. The stimulated emission peak was observed at ∼3.48 eV, which is ∼50 meV lower than that of spontaneous emission. The excitation power dependence on the emission intensity clearly indicates threshold pump power density of 0.75 MW/cm2 for the onset of stimulated emission.