Effects of interface charge distribution on anomalous luminescence phenomenon of quaternary AlInGaN multiple quantum well light-emitting diodes

Li, Chia-Hao; Wang, Cheng-Kang; Chen, Wan-Yi; Wang, Wei-Tzer; Hung, Cheng-Wei; Ke, Chih-Chun; Wang, Jen-Cheng; Shen, Hui-Tang; Nee, Tzer-En; Hu, Yeu-Jent; Lee, Jiunn-Chyi; Wu, Ya-Fen; Fang, Chia-Hui Taiwan

The III-Nitride-based low dimensional multiple quantum well (MQW) heterostructures has been popularly investigated in past decade. In spite of this striking advanced technology, the emission process is affected by several peculiarities of this materials system and is still under debate. In this work, we investigate the anomalous temperature characteristics of the quaternary AlInGaN MQW structures with different barrier widths, in depth via an examination of the luminescence intensity and carrier transport temperature evolution. It is found that the ideality factor of two devices increase with decreasing temperature from 300 K to 20 K. For these, we employ Levineˇ¦s model to characterize this anomaly and acquired the ideality factor as function of temperature is give by n=1+ To/T. The so-called pseudo-temperature To is a voltage-dependent parameter associated with the interfacial state distribution at heterojunction. 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 To and attributed to carrier tunneling behavior. We can observed that the devices with narrower barrier width inherently exhibit a large pseudo-temperature To with a large characteristic energy and more interfacial state charge fluctuation of the multilayer interface, over a variety of temperature and voltage ranges. Due to the more interface state distribution and the less effective density of state (DOS), the excitons formed in a devices with narrower barrier width 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 To and further characteristic energy, result in the abnormal deterioration of the luminescence intensities with small DOS for the narrower barrier width device above 180 K. Accordingly, the MQW with a wider barrier width not only significantly increase carrier confinement and improve the quantum efficiency, but also reduce the interface-state charge fluctuations. All observed correlations suggest that the carrier transport process is essentially responsible for the improvement of the luminescence characteristic.

---

back