AlGaN nanowire deep ultraviolet LEDs with polarization enhanced tunnel junction and p-AlGaN layer by molecular beam epitaxy

Abstract

In this work, we report the growth, fabrication, and characterization of aluminum gallium nitride (AlGaN) nanowire deep ultraviolet light-emitting diodes with a polarization engineered tunnel junction (TJ) and p-AlGaN layer. The major takeaway from this study is: first, devices emitting at around 250 nm with a maximum external quantum efficiency of around 0.01% are demonstrated. Second, the effect of the electric polarization field in the n+-Al0.1Ga0.9N/GaN/p+-Al0.1Ga0.9N TJ due to the incorporation of the GaN layer is observed by comparing the current-voltage (I–V) characteristics of devices with different GaN thicknesses. The incorporation of the GaN layer improves the I–V characteristics due to the improved tunneling process originating from the band bending induced by the polarization charges at GaN and AlGaN heterointerfaces. Third, the role of the graded p-AlGaN layer on the device's electrical performance is also elucidated. It is found that the graded p-AlGaN layer plays a significant role in improving the device electrical performance. Finally, the improved device electrical performance also transfers to the device optical performance.