Fabrication of high-lumen InGaN flip chip LEDs

The factors critical to the fabrication of high-lumen InGaN flip chip LEDs are discussed. It is shown that as the die size and the current density increase, the n-GaN sheet conductivity becomes extremely critical to uniform current spreading and the corresponding uniformity of light emission. It is observed that a thick p-metal is important in reducing hot spot formation. The p-contact is also critical to increasing light extraction efficiency and wall-plug efficiency. The merits and reliability of Al- and Ag-based p-contacts are compared. Reliability issues related to the n-contact are also discussed. Finally, performance data for InGaN blue lamps, for drive currents up to 900 mA is shown.