Recombination lifetime in InGaN/GaN based light emitting diodes at low current densities by differential carrier lifetime analysis

Carrier lifetimes of the recombination processes in light emitting diodes (LEDs) depend strongly on the operating point. We measure the carrier lifetimes of InGaN/GaN LEDs at low current densities by applying the differential carrier lifetime analysis. In the measurement setup the LED is driven with constant current modulated with small amplitude alternating current (AC) and the carrier lifetime is obtained from the phase difference between input AC and light output. In addition to the optical method, we also extract the lifetimes directly from the capacitance and differential resistance of the LED obtained using an impedance analyzer and compare the results to lifetimes obtained by the optical setup. The carrier lifetimes were found to increase from hundreds of nanoseconds to microseconds when the current density was decreased from tens of A/cm(2) to tens of mA/cm(2). Both measurement methods resulted in similar lifetimes. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim