High brightness GaN-based flip-chip light-emitting diodes by adopting geometric sapphire shaping structure

Abstract

GaN-based flip-chip LEDs (FC-LEDs) with geometric sapphire shaping structure were fabricated. The sapphire shaping structure was formed on the bottom side of the sapphire substrate by the chemical wet etching technique for the purpose of light extraction. The crystallography-etched facets were `(1 0 1 0) M-plane, (1 1 0 2) R-plane and (1 1 2 0) A-plane against the (0 0 0 1) c-axis with the angles range between similar to 29 degrees and similar to 60 degrees. It is demonstrated that the geometrical shape of the sapphire windows layer improves the light extraction efficiency. Compared to the conventional FC-LED, the sapphire-shaped FC-LED significantly enhanced the output power. The light output power of sapphire-shaped FC-LEDs was increased by 55% (at 350 mA current injection) compared to that of conventional FC-LEDs.