Theoretical and experimental study of thermal resistance & temperature distribution in high-power AlGaInN LED arrays

The driving current, chip area of high-power AlGaInN light emitting diodes (LEDs) and the level of integration of LED arrays are continuously increased to provide ever higher output light flux. The new developments require more attention to pay to the thermal management of LEDs, commonly assessed in terms of the thermal resistance. Temperature distribution in a LED array and its effect on the chip thermal resistance has been studied both theoretically and experimentally. The thermal measurements were performed with the help of a temperature-sensitive parameter - forward voltage drop on the p-n junction under the action of heating current. Two methods of heat exciting were used: step-like or harmonically pulse-width modulated heating current. Analysis of forward voltage relaxation at transient thermal processes allows determination of thermal impedance components corresponding to the structural elements of the LEDs and arrays. The temperature distribution in the LED array predicted by coupled simulations of the heat transfer agrees well with the experimental measured temperature mapping by the IR-microscopy.