The Interrelation between Temperature and Power Supply Modes of Low Power High Efficiency Light Emitting Diodes

Abstract

The studies of interrelation between temperature and power supply modes of low power high efficiency light emitting diodes and the effect of temperature on their direct voltage were analysed. It is discovered that there are significant differences in the experimental data on temperature modes obtained by many authors. A new dynamic method of measurement of overheating temperature in the active region of p-n structures at pre-set direct current is applied. This method is based on registration of the transient processes of direct voltage changes during heating by pre-set current and cooling-down after switching-off of the heating current at constant low direct current. The formula is obtained for calculation of the proportion factor of direct-voltage temperature dependence for diodes with different techno structures accounting for the measurement current, the non-ideality factor of the voltage-current curve, and temperature. The experimental curves of the LED active region temperature dependence on heating current at its density of (10–110) A/cm2 and dissipated power of (0.025–0.45) W are obtained. The direct-voltage temperature dependence proportion factor was modelled at different values of measurement current for specific LEDs. It is demonstrated that the active region of LEDs based on wide-band-gap semiconductors overheats due to formation of hot charge carriers interacting with optic phonons in it at current densities, when the exponential nature of the voltage-current curve is disturbed.