Effect of quantum well shape and width on deep ultraviolet emission in AlGaN nanowire LEDs

The effect of quantum well shape and width on the emission properties of nanowire ultraviolet LEDs is experimentally investigated. Nanowire LEDs are grown by plasma-assisted molecular beam epitaxy and their electroluminescence is compared. A two- to three-fold increase in optical output is observed from 5nm wide parabolic quantum wells compared with square quantum wells. This increased output is attributed to the both increased electron-hole overlap in agreement with band edge modeling, and supports previous theoretical predictions of decreased Auger recombination due to softening of the potential well in parabolic quantum wells. It is experimentally observed that when the quantum well width is decreased to 2nm, the parabolic quantum wells exhibit a twofold output improvement over the square wells at low injection. However, at high current injection, the parabolic and square quantum wells perform similarly. Peak emission wavelengths for the nanowire LEDs is pushed into the deep ultraviolet by decreasing the AlGaN quantum well width. The emission wavelength shifts from 315 to 290nm when the width is decreased from nominally 5 to 0.5nm.