Cubic InGaN/GaN multi-quantum wells and AlGaN/GaN distributed Bragg reflectors for application in resonant cavity LEDs

In this contribution, we present results on the growth and characterization of c-InGaN/GaN MQWs and c-AlGaN/GaN DBRs, which may be used as building blocks of green (510 nm) resonant cavity light emitting diodes, which have a high potential as light sources for local area networks using plastic optical fibers. First, the impact of the indium and gallium flux on the growth of cubic-InGaN by plasma assisted molecular beam epitaxy has been studied. Indium is observed to incorporate into the c-GaInN films only when the gallium flux is reduced significantly below the value needed for stoichiometric c-GaN growth. A decrease of the surface roughness of the InGaN layers and an increase of their photoluminescence intensity per unit thickness at the transition from metal-flux limited to active nitrogen-limited growth is observed. High quality c-InGaN/GaN multi-quantum wells were grown with superlattice peaks clearly resolved in high resolution X-ray diffraction and a strong room temperature photoluminescence with a full width at half maximum of 240 meV. Cubic-AlGaN/GaN distributed Bragg reflectors with a maximum reflectivity of about 50% at 515 nm and a stop bandwidth of 33 nm have been realized. Enhanced 526 nm room temperature photoluminescence has been observed from a combined structure of a c-InGaN/GaN multi-quantum well and a c-AlGaN/GaN distributed Bragg reflector.