Comparison of temperature dependent electroluminescence of InGaN/GaN and AlGaInP based LEDs

Light emitting spatial inhomogeneity in InGaN/GaN multiple quantum well (MQW) blue and green LEDs were observed directly with a microscope. Electroluminescence (EL) spectra of InGaN/GaN QW blue and green LEDs were studied in the temperature range of 10-300 K at an injection current of 5mA. Some anomalous behavior was observed. Intensity of the EL main peak increased monotonically with temperature from 10 to 200 K and slightly decreased with further temperature increase in the 200 K range. This is in contrast with the monotonic decrease of EL with increasing temperature for conventional AlGaInP QW red LEDs. The anomalous behavior can only be observed on InGaN/GaN systems. The origin of such behaviors was discussed using a model of quantum dot clusters in the InGaN/GaN psudo-quantum wells, with a small potential barrier at the boundary of the quantum dots.