Current and temperature dependent characteristics of deep-ultraviolet light-emitting diodes

The electrical and optical characteristics of the 340- and 280-nm AlGaN-based deep-ultraviolet multiple-quantum-well light-emitting diodes (LEDs) at low temperatures (5-300 K) and various injection currents were studied. The negligible blue shift of the peak energy with increasing current density and monotonic blue shift with decreasing temperature suggest the absence of localized state emission. In the 340-nm LED, a band-tail state emission centered at 353 run was dominated at low currents around 150 K, whereas the 280-mn LED exhibited minimal defect emission over the entire temperature range. The internal quantum efficiencies of both LEDs at room temperature were found to be less than 5%, indicating that there is significant room for improvement in structure design and material quality.