Interdigitated Multipixel Arrays for the Fabrication of High-Power Light-Emitting Diodes With Very Low Series Resistances, Reduced Current Crowding, and Improved Heat Sinking

The paper reports on a novel mask design consisting of interdigitated multipixel arrays for the fabrication of high-power light-emitting diodes (LED) with very low series resistance, reduced current crowding, and improved heat sinking. The reduction in the series resistance was mainly achieved by reducing the bulk n-resistance and the n-contact resistance, and by increasing the effective perimeter of the mesa. The small dimension of the individual pixel improved the lateral current spreading. The distributed matrix of the micropixels also resulted in an improved thermal management, effectively rendering a high cw drive-current operation. Thermal simulations showed that the junction temperature for large area power chips dropped by more than 60% by adopting the new mask design. Significant improvement in electrical and optical performances was observed when the mask was applied to a 400 nm InGaN/GaN blue LED wafer, as compared to a standard square-shaped LED with an equal active area and fabricated from the same epitaxial wafer. Series resistance as low as 0.5 Omega was measured for 300 mum devices. On a Cu header, a peak output power of 115 mW was obtained at 3.15 A cw drive current. A 700 mum LED on a header had a peak output power of 200 mW at 3.15 A cw drive current