GaN/AlN multiple quantum wells grown on GaN-AlN waveguide structure by metalorganic vapor-phase epitaxy

High-optical-confinement waveguide structure based on nitride semiconductors is proposed and demonstrated for the first time with metal organic vapor-phase epitaxy. The waveguide structure composed of 1-mu m-thick AlN cladding layer, 2-mu m-thick GaN guiding layer, and 40 periods of GaN/AlN multiple quantum wells (MQWs) was grown using optimized growth conditions for each layer. For improved material quality, the two-step growth technique using low-temperature AlN and GaN nucleation layers was utilized to reduce the stress induced by lattice mismatch between each layer. The high-optical-confinement structure could therefore be grown with high quality, leading to a successful observation of inter-sub-band absorption in GaN/AlN MQWs. The inter-sub-band absorption wavelength observed in such structure is in good agreement with that of MQWs grown on GaN layer, showing that the proposed waveguide structure can be used as a standard structure for optical devices based on inter-sub-band absorption.