Carrier distribution characteristics of AlGaN-based ultraviolet light-emitting diodes at elevated temperatures

We studied the electrical and optical properties of 276 nm and 306 nm AlGaN-based ultraviolet light emitting diodes (UV-LEDs) in the temperature range of 303–403 K. Capacitance–voltage measurements were performed to extract the carrier distribution in UV-LED, especially around the multi-quantum well structure. Our results showed that an additional carrier concentration peak close to the first quantum well of the p-n junction was present at elevated temperatures. Our physical simulation 276 nm LEDs revealed the cause of the concentration change to be the higher stress of the barrier layer with the temperature increase which introduced additional piezoelectric charge at the heterostructure interfaces. It is also found that the electron barrier layer (EBL) acceptor concentration decreased with the temperature, which caused a shift in the carrier concentration peak position, corresponding to higher EBL contribution to the increase of depletion width in the UV-LED. Higher temperatures lead to the increase of polarization charge at the quantum barrier/EBL interface, associated with downward bending of the conduction band of the quantum barrier, which is possibly the reason for an additional carrier concentration peak. The variation of the carrier distribution in UV-LED with temperature provides a new perspective and method to explain the UV-LED thermal droop effect.