Improvement of crystal quality of AlGaN multi quantum well structure by combination of flow-rate modulation epitaxy and AlN/GaN multi-buffer layer and resultant lasing at deep ultra-violet region

The crystal quality of AlN and AlGaN MQW layers was improved greatly by a combination of flow-rate modulation epitaxy (FME) and the optimized AlN/GaN multi-buffer layer in low-pressure metal organic vapor phase epitaxy (LP-MOVPE). The cross-sectional TEM image indicated that the threading-dislocation density of the AlN template decreased from 10(9)-10(10) cm(-1) to 10(7)-10(8) cm(-2) by this combination. Resultantly, the lasing wavelength with the same optical pumping power decreased by about 80 nm, and lasing at 241 nm, the shortest reported so far at room temperature, has been achieved.