Effect of low hole mobility on the efficiency droop of AlGaN nanowire deep ultraviolet light emitting diodes

Compared to the extensive studies on the efficiency droop of InGaN visible light emitting diodes (LEDs), the efficiency droop of AlGaN deep ultraviolet (UV) LEDs is much less studied. In this context, we discuss the efficiency droop of AlGaN ternary nanowire deep UV LEDs. The device active region consisted of AlGaN double heterojunctions, which were grown by molecular beam epitaxy on silicon substrates. Through detailed analysis of the device optical characteristics under both continuous-wave and pulsed operations, as well as of the electrical characteristics from 293 K to 77 K, it is suggested that the efficiency droop is largely rooted in the low hole mobility, due to the dominant Mg impurity band conduction at room temperature in highly p-doped AlGaN alloys.