Time of carrier escape and recombination coefficients in InGaN quantum-well active regions of blue, cyan, and green light-emitting diodes

Addressing the recently observed unexpected low-current saturation of differential carrier lifetime (DLT) in the active region of InGaN-based light-emitting diodes (LEDs), a novel procedure is suggested for the evaluation of both escape time of carriers from the InGaN quantum wells and their recombination coefficients. The procedure uses coupled measurements of external quantum efficiency and DLT as a function of LED continuous-wave operating current. The procedure has been applied to three LEDs with InGaN multiple quantum well (QW) active regions emitting blue, cyan, and green light. Laser diodes operating at different wavelengths were employed for small-signal resonant pumping of the LED active regions in order to understand a possible dependence of the escape time and recombination coefficients on the excitation wavelength. The revealed wavelength dependence of the Shockley-Read-Hall recombination coefficient in the green LED is attributed to lateral non-uniformity of the InGaN QW with high Indium content. The radiative and Auger recombination coefficients evaluated by the above procedures in all three LEDs turned out to be close to those reported earlier for the LEDs with single QW active regions. The obtained recombination coefficients are used for further performance comparison of the studied devices. The suggested procedure is helpful for the investigation of carrier escape and the optimization of III-nitride devices, such as photodetectors, solar cells, and quantum-cascade lasers.