Carrier recombination mechanisms in nitride single quantum well light-emitting diodes revealed by photo-and electroluminescence J. Appl. Phys.Efficient blue light-emitting diodes with InGaN/GaN triangular shaped multiple quantum wellsThe carrier transport and recombination dynamics of monolithic InGaN/GaN light-emitting p-n junction structures with two active regions are investigated. Room-temperature and low-temperature photoluminescence and room-temperature electroluminescence measurements show two emission bands originating from the two active regions. In electroluminescence, the intensity ratio of the two emission bands is independent of injection current. In contrast, the intensity ratio depends strongly on the excitation intensity in photoluminescence measurements. The dependency of the emission on excitation is discussed and attributed to carrier transport between the two active regions and to the different carrier injection dynamics in photoluminescence and electroluminescence. The luminous efficacy of a Gaussian dichromatic white-light source is calculated assuming a line broadening ranging from 2kT to 10kT. Luminous efficacies ranging from 380 to 440 lm/W are obtained for broadened dichromatic sources.

Perpendicular transport characteristics of n-type AlxGa1−xN/GaN superlattices are presented. Planar and mesa-etched superlattice structures are employed to identify the perpendicular resistance. Perpendicular transport measurements in Al0.22Ga0.78N/GaN superlattices display linear current–voltage characteristics with a resistivity that is a factor of 6.6 higher than for bulk material. A theoretical model is developed for perpendicular transport in AlxGa1−xN/GaN superlattices based on sequential tunneling. The model shows that short superlattice periods are required to minimize the perpendicular resistivity.