Performance Enhancements of Flip-Chip Light-Emitting Diodes With High-Density n-Type Point-Contacts

Novel gallium nitride-based flip-chip light-emitting diodes (FCLEDs) with high-density distributed n-type point-contacts were designed and fabricated. With high density and uniformly distributed n-type point-contacts, the point-contact (PC) FCLEDs had higher light output power (LOP) by 18% over the reference flip-chip LED with conventional contacts fabricated from the same wafer. The forward voltage of the PC-FCLEDs was 0.16 V lower than the reference FCLED and the wall-plug efficiency was increased by 24% at the same current level. The maximum LOP of the PC-FCLEDs measured at 2.4 A was 43% more than the maximum obtained by the reference LED at 1.8 A. It was also found that the PC-FCLEDs suffered lower efficiency droop. The optical performance improvement of the PC-FCLEDs is attributed to an increase of the light extraction and the uniform carrier distribution, which results from the small and high density deeply etched holes and PCs. The electrical performance was enhanced through a minimized lateral current spreading distance.