Reducing Heat Crowding in InGaN/GaN Flip-Chip Light-Emitting Diodes with Diamond-Like Carbon Heat-Spreading Layers

Removal of the heat crowding phenomenon in flip-chip light-emitting diodes (FCLEDs) with diamond-like carbon (DLC) heat-spreading layers on a ceramic submount is investigated. The wetting area of the chip and ceramic submount is critical for the die attachment process. Good DLC thermal diffusivity enhances heat spreading in the FCLED chip area. During the relative surface temperature distribution measurement, the heat crowding phenomenon was not observed in the FCLED with the DLC heat-spreading layer. During the lifetime testing of 1008 h at an ambient temperature of 85 °C and a humidity of 85%, the light intensity of the FCLED with the DLC heat-spreading layer improved by 2% at the standard operating current (350 mA). At injection currents three times the standard operating current (1000 mA), the light intensity in the FCLED with the DLC heat-spreading layer was improved by 11% compared to that in the FCLED without the DLC heat-spreading layer. The junction temperature of the FCLED with the DLC heat-spreading layer was lower than that of the FCLED without the DLC heat-spreading layer by 9 °C. Therefore, FCLEDs with a DLC heat-spreading layer can improve thermal management and die attachment yields.