Improved performance of deep ultraviolet AlGaN-based light-emitting diode by reducing contact resistance of Al-based reflector

In this study, chlorine (Cl) treatment was carried out on p -AlGaN to enhance the performance of ultraviolet-C light emitting diodes (UVC LEDs) by modifying ITO work function and hence reducing the contact resistance of ITO/Al reflector. The Cl-treated UVC LEDs exhibit the forward voltage of 6.88 V at 20 mA, whereas the reference samples show 7.50 V. The light output power and relative wall plug efficiency (WPE) of the Cl-treated UVC LEDs are enhanced by 17.1% at 500 mW and 19.5% at 100 mA, respectively, as compared to the reference. Additionally, the Cl-treated LEDs also display reduction in both the leakage current and ideality factor. Further, the photoluminescence (PL) intensity of AlGaN micro-disks is also enhanced by the Cl-treatment. X-ray photoemission spectroscopy (XPS) results indicate the formation of Cl-ITO at the ITO/ p -AlGaN interface and the passivation of the surface states of AlGaN by Cl radicals. Based on the XPS results, a possible mechanism for the improved performance of Cl-treated UVC AlGaN-based LEDs is described and discussed. • We first adopted Cl-treatment of p-AlGaN to enhance the efficiency of UVC LEDs. • Cl-treatment increases the work function of ITO and passivates AlGaN surface. • Cl-treated LEDs give lower forward voltage and leakage current, and higher efficiencythan reference. • Cl treatment is found to be stable for a long time (e.g., 5 months). • Cl-treatment has proven to be a highly promising process for the fabrication of highefficiencyUVC LEDs.