Anomalous temperature behaviour and band tailing in InGaN/GaN heterostructures grown on sapphire by MOCVD

Summary form only given. InGaN is very attractive as the active region material for optoelectronic devices emitting near-UV and blue/green light. However, in spite of tremendous progress in realization of GaN/InGaN/AlGaN light-emitting diodes and diode lasers, the underlying fundamental processes of carrier recombination in InGaN are still poorly understood. For example, controversies surround the role of localized excitons in optical gain, or self-formation of quantum dots in InGaN. Light emission from single-quantum-well (SQW) blue and green light emitting diodes (LEDs) was studied extensively, and it was shown that their unusual temperature, current, and hydrostatic pressure behavior was consistent with involvement of density-of-states (DOS) band tails in the optical emission process. In the paper, we demonstrate that thicker InGaN/GaN heterostructures exhibit behavior similar to that observed in SQW LEDs. Samples under study were grown on (0001) sapphire substrates by atmospheric-pressure metal-organic chemical-vapor deposition (MOCVD).