Influence of the deposition time of barrier layers on optical and structural properties of high-efficiency green-light-emitting InGaN/GaN multiple quantum wells

We reported the effect of the deposition time of barrier layers on optical and structural properties of high-efficiency green-light-emitting InGaN/GaN multiple quantum wells (MQWs) by photoluminescence (PL) and high-resolution x-ray diffraction techniques. The MQW samples on (0001)-plane sapphire substrates were prepared with a ramping method by metalorganic chemical deposition. It was found that the structural or interface quality of the MQW system improved as the deposition time of barrier layers increased from 10 to 14 min, but lattice relaxation was still observed. The relaxation degree decreases from 33% to 6% as the deposition time increases. Temperature-dependent PL measurements from 12 to 300 K indicated that the integrated PL intensities start to decay rapidly as temperature rises above 50 K for the sample with the shorter deposition time, and above 100 K for the sample with the longer deposition time. The luminescence thermal quenching of the two samples suggests the two nonradiative recombination centers based on a fit to Arrhenius plot of the normalized integrated PL intensity over the entire temperature range. The first centers at higher temperatures show less difference for the two samples. The second centers at lower temperatures can be attributed to the trapping of carriers at the rough interface for the sample with the shorter deposition time and to the thermal quenching of bo- und excitons for the sample with the longer deposition time, respectively.