Recent developments in InGaN - based blue LED's and LD's

UV/blue/green/amber InGaN quantum-well structure light-emitting diodes with an external quantum efficiency of 7.5%, 11.2, 11.6% and 3.3% were developed. The localization in the InGaN well layer induced by the In composition fluctuations seems to be a key role of the high efficiency of those InGaN-based light-emitting diodes. When the electrons and holes are injected into the InGaN active layer of the light-emitting diodes, these carriers are captured by the localized energy states before they are captured by the nonradioactive recombination centers caused by the large number of threading dislocations. InGaN multi-quantum-well structure laser diodes with modulation doped strained-layer supperlattice cladding layers grown on the espitaxiall lateral overgrown GaN substrate were demonstrated to have an estimated lifetime of more than 10000 hours under-room temperature continuous-wave operation. When the laser diode was formed on the GaN above SiO2 mask region without any threading dislocations, the threshold current density was as low as 2.7 kAcm-2. When the laser diode was formed on the window region with the light threading dislocation density, the threshold current density was as high as 4.5 to 9 kAcm-2. A leakage current due to a large number threading dislocations caused the high threshold current density on the window region. (author)