Thermal measurements and analysis of AlGaInP/GaInP MQW red LEDs with different chip sizes and substrate thicknesses

Thermal properties of AlGaInP/GaInP MQW red LEDs are investigated by thermal measurements and analysis for different chip sizes and substrate thicknesses. To extract the thermal resistance (Rth), junction temperature (Tj) is experimentally determined by both forward voltage and electroluminescence (EL) emission peak shift methods. For theoretical thermal analysis, thermal parameters are calculated in simulation using measured heat source densities. The Tj value increases with increasing the injection current, and it decreases as the chip size becomes larger. The use of a thin substrate improves the heat removal capability. At 450 mA, the Tj values of 315 K and 342 K are measured for 500 × 500 μm2 LEDs with 110 μm and 350 μm thick substrates, respectively. For 500 × 500 μm2 LEDs with 110 μm thick substrate, the Rth values of 13.99 K/W and 14.89 K/W are obtained experimentally by the forward voltage and EL emission peak shift methods, respectively. The theoretically calculated value is 13.44 K/W, indicating a good agreement with the experimental results.