Effect of excitonic interactions on abnormal luminescence behaviour of InGaN/GaN light-emitting diodes with electron tunneling layer

We studied the unique correlations between the electrical and optical characteristics of InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) with n-AlGaN layer and n-InGaN/GaN superlattice electron tunneling layer (ETL). It was found that the ideality factor of the two devices increased with decreasing temperature from 300 to 20 K. Levine's model was used to characterize the anomaly, and the ideality factor could be shown as a function of temperature by n = 1 + T_o/T. The device with ETL inherently exhibited a large pseudo-temperature T_o with a large characteristic energy and charge population in the multilayer interface, over wide temperature and voltage ranges. Owing to the more interface state distribution and the less effective density of state (DOS) in the quantum wells, the excitons formed in the ETL sample augment the spectral radiations at temperatures higher than 150 K. The carrier tunneling processes via the extent of charge population consequently caused anomalous T_o and resulted in the abnormal deterioration of the EL intensities with a small density of state.