Analysis of below-threshold efficiency characteristics of InGaN-based blue laser diodes

Abstract

In this study, we investigate the below-threshold emission characteristics of InGaN-based blue laser diodes (LDs) emitting at 442 nm to study the efficiency droop effects in InGaN LDs. From the measurement of spontaneous emission in the LD, it is observed that the peak efficiency appears at a current density of similar to 20 A/cm(2) and the efficiency at the threshold current density of similar to 2.3 kA/cm(2) are reduced to similar to 47% of the peak efficiency. The measured spontaneous emission characteristics are analyzed using the carrier rate equation model, and the peak internal quantum efficiency is found to be similar to 75% using the fit of the measured efficiency curve. In addition, the Auger recombination coefficient of the measured InGaN blue LD is found to be 10(-31)-10(-30) cm(6)/s, which is somewhat lower than that reported for InGaN-based blue light-emitting diodes. It is discussed that low dislocation density and uniform current injection in quantum wells may have resulted in the low Auger recombination coefficient of InGaN LDs. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759247]