Core-shell nanorods as ultraviolet light emitting diodes

Existing barriers to efficient deep UV LEDs may be reduced or overcome by moving away from conventional planar growth and towards three dimensional nanostructuring. Nanorods have the potential for enhanced doping, reduced dislocation densities, improved light extraction efficiency and quantum wells free from the quantum confined Stark effect. Here, we demonstrate a hybrid top-down/bottom-up approach to creating highly uniform AlGaN core-shell nanorods on sapphire repeatable on wafer scales. Our GaN-free design avoids self-absorption of the quantum well emission, while preserving electrical functionality. The effective junctions formed by doping of both the n-type cores and p-type caps were studied using nanoprobing experiments where we find low turn on voltages, strongly rectifying behaviours and significant electron beam induced currents. Timeresolved cathodoluminescence measurements find short carrier liftetimes consistent with reduced polarisation fields. Our results show nanostructuring to be a promising route to deep-UV emitting LEDs, achievable using commercially compatible methods.