Algainp Red-Emitting Light Emitting Diode Under Extremely High Pulsed Pumping

Efficiency of commercial 620 nm AlGaInP Golden Dragon-cased high-power LEDs has been studied under extremely high pump current density up to 4.5 kA/cm(2) and pulse duration from microsecond down to sub-nanosecond range. To understand the nature of LED efficiency decrease with current, pulse width variation is used. Analysis of the pulse-duration dependence of the LED efficiency and emission spectrum suggests the active region overheating to be the major factor controlling the LED efficiency reduction at CW and sub-microsecond pumping. The overheating can be effectively avoided by the use of sub-nanosecond current pulses. A direct correlation between the onset of the efficiency decrease and LED overheating is demonstrated.