Experimental study of electroluminescence and temperature distribution in high-power AlGaInN LEDs & LED arrays

Comprehensive analysis of current spreading, temperature distribution, and near-field electroluminescence of high-power “face-up” AlInGaN LEDs and LED Arrays was performed by combination of different experimental methods. Measurement results of thermal impedance and temperature distribution (mapping) of powerful light-emitting diode assemblies are described. A thermal resistance characterization consists in investigations of transient processes of temperature-sensitive parameter under heating by step-form or harmonically pulse-width modulated direct current and analysis using a thermal equivalent circuit (the Cauer and Foster models). By the involved method, thermal resistances of internal elements of the LEDs are determined. At the same time high resolution mapping of EL and thermal radiation was obtained by optical microscope and infrared images technique. It has been established correlation of the thermal resistance with a change in the current distribution (current crowding) at high excitation levels.