Surface-state charge fluctuations on the carrier dynamics in InGaN/GaN blue light-emitting diodes with multiquantum barriers

In this article, we investigate the anomalous temperature characteristics of InGaN/GaN multiple quantum-well (MQW) blue light emitting diodes (LEDs), with multiquantum barriers (MQBs) and GaN barriers, in depth via an examination of the luminescence intensity and carrier transport temperature evolution. The experimental evidences for electrical properties of two diodes exhibited the ideality factor extremely departure from unity, and the anomalies were characterized by pseudo-temperature T_o and carrier tunneling behavior. With respect to conventional GaN barrier devices, devices with MQBs inherently exhibit a small pseudo-temperature T_o with a small characteristic energy and charge population of the multilayer interface, over a variety of temperature and voltage ranges. Due to the less interface state distribution and the more effective density of state (DOS), the excitons formed in the MQB sample augment the spectral radiations at the temperature higher than 180 K. Furthermore, the carrier tunneling processes via the extent of the charge population consequently cause anomaly more T_o and further characteristic energy, result in the abnormal deterioration of the EL intensities with small DOS for these two LEDs below 180 K. These results also demonstrate that an introduction of well-designed barriers within a heterojunction configuration can be used to perform device improvements by governing the coupling of dynamical transports to spontaneous emissions. All observed correlations suggest that the carrier transport process is essentially responsible for the improvement of the luminescence characteristic. Accordingly, the MQW with the well-designed MQB structures not only exhibited the thermal-insensitive luminescence, but also inhibited the energetic carrier overflow.