Suppressing spontaneous polarization of p-GaN by graphene oxide passivation: enhanced light output of flexible UV-LED

GaN-based ultraviolet (UV) LEDs are widely used in numerous applications, including white light pump sources, high-density optical data storage, medical equipment, and counterfeit bill detection. However, low hole injection... [ view full abstract ]

GaN-based ultraviolet (UV) LEDs are widely used in numerous applications, including white light pump sources, high-density optical data storage, medical equipment, and counterfeit bill detection. However, low hole injection rate in p-type region due to poorly activated holes and spontaneous polarization leads to insufficient light emission efficiency. Therefore, improving hole injection rate is a key step towards high performance UV-LEDs to expand their uses. Here, we report a new method for enhancing light output power of UV-LEDs by increasing hole injection rate in p-type region. This was achieved by simply passivating graphene oxide (GO) on top of the fully fabricated LED. The dipole field formed by the passivated GO and indium tin oscide (ITO) junction enhanced hole injection rate in p-type region and simultaneously increased hole concentration by about 60%. This not only improved the homogeneity of electroluminescence intensity in active layers but also enhanced light output power to about 60% in linear current region and almost twice in saturated current region due to the delayed hole saturation. Our simple approach of overcoming the limited carrier concentration of p-type GaN using GO passivation method disrupts the current state of the art technology and will be useful for high-efficiency and flexible UV-LED technology.