Improvement of carrier confinement in blue light emitting diode with InGaN/GaN multiquantum barriers

Temperature-dependent electroluminescence (EL) of blue InGaN/GaN multiquantum-well light-emitting diodes (LEDs) has been systematically investigated to illustrate the role of multiquantum barrier (MQB) in carrier capture and recombination. With recent advances in nitride-based light-emitting diodes (LEDs), the importance for the development of high brightness as well as high temperature devices is profound. It is found that, when temperature is slightly decreased to 200 K, the EL intensity of the active region efficiently increases in both devices, as usually seen due to the improved quantum efficiency. However, with further decrease of temperature down to 20 K, unusual reduction of the integrated EL intensity of the active region is commonly observed for both of the two diodes, accompany with the appearance of the high energy band which can be assigned as Mg-related transition at relative low temperature. It also clear noted the the diode without MQB shows a faster reduction tendency of the EL intensity than the one with MQB. Based on a rate equation analysis, we found that not only the radiative recombination zone of the quantum well region less shift to the p-type GaN region for device with MQB, but also the intensity of Mg-related transition in the LED with MQB are more than one order of magnitude less than the one without MQB. These results further verify the effective carrier confinement in active region, less carrier leakage over the barrier, and improvement of the luminescence efficiency by MQBs. All the calculations are agreement with the experimental observations.