Heat sink performances of GaN/InGaN flip-chip light-emitting diodes fabricated on silicon and AlN submounts

Fabricating flip-chip light emitting diodes (FCLEDs) with two good thermal conductivity materials of silicon and aluminum nitride (AlN) as submount are investigated on its output power and heat sink capacity. It is known that many advantages exist in FCLED structures. In addition to the upward emitting light, the downward propagating light is reflected up by a high reflectance contact, increasing the light extraction. The heat generated in the LED flows directly through the interconnect metal of the submount, improving thermal conduction. Except blue shift at the low current injection region (0-0.3 A), the heat induced bang gap narrowing (red shift) at high current injection region (0.3-0.7 A) is observed with a red shift of 8.92 nm for conventional LED, 4.62 nm for silicon submount FCLED, and only 2.87 nm for AlN submount FCLED. The light intensity of FCLEDs with silicon and AlN submounts exhibits 1.6 and 7 times at an injection current of 0.35 and 0.7 A, respectively, larger than that of conventional LED.