Study on the Electron Overflow in 264 nm AlGaN Light-Emitting Diodes

The dependence of electron overflow on injection current, operating temperature, and structure of p-type layers was investigated in 264 nm AlGaN light-emitting diodes (LEDs). Both increasing current and decreasing temperature resulted in the increase of electron overflow due to the insufficient barrier height and the increase of electrical field in p-type layers, respectively. The use of heterostructure as p-type layer was more favorable to suppress the overflow than single layer owing to the higher barrier for electron overflow and the lower barrier for hole injection induced by the polarization field. Both simulation and experiment showed that the insert of thin i-AlN interlayer between active region and p-type layers can suppress the electron overflow effectively due to the further increase of barrier height. The optical properties of such LEDs were improved significantly and the maximum output power was increased by two orders of magnitude.