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

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.