Fabrication and Characterization of Flip-Chip Power Light Emitting Diode with Backside Reflector

The electrical, optical, and thermal characteristics of flip-chip (FC) GaN-based light-emitting diodes (LEDs) with and without backside aluminum (Al) reflector have been investigated. The LEDs were mounted on the silicon (Si) sub-mounts which have superior thermal conductivity (150 W/m·K), and the Au stub bumps were used as the interconnecting metal to achieve the FC bonding process. Compared with the conventional FC-free LED, the light extraction and thermal conduction of FC LED have been improved and no significant degradation of forward and reverse I-V characteristics are observed. Moreover, adding a backside Al reflector can further enhance upward light emission. The optimum numbers of Au stub bumps are 24, that is, the optimum total area of Au stub bumps is about 22.8×10 4 μm 2 for a 1 mm×1 mm LED chips.