Carrier lifetime in 1.3 μm InAs quantum-dot lasers using small-signal modulation technique

Abstract

Carrier lifetime measurements are a powerful tool to understand and quantify the recombination mechanisms in semiconductor lasers. In this work we report the results of carrier lifetime measurements performed on 1.3 μm p-doped InAs Quantum-Dot lasers at room temperature using the small-signal modulation technique. The carrier lifetime at a particular bias current is determined by fitting the measured optical frequency response curves to the calculated response derived from sub-threshold carrier and photon rate equations. Calculated optical response curves are dominated by a single pole regardless of whether a single or multiple carrier level rate equation analysis is used. We also measure a single pole optical response, throughout the entire range of bias currents, thus allowing us to extract the differential carrier lifetime. The recombination coefficients are extracted by simultaneously fitting the variation of differential carrier lifetime with bias current to equations relating the current and carrier lifetime to the recombination coefficients and carrier density. Specifically we find a cubic (or Auger) recombination coefficient of 1.2 x 10^-29 cm⁶/s and 5.6 x 10^-29 cm6/s in the single and multi carrier level rate equations respectively, while the bimolecular (radiative) coefficients are 1.8 x 10^-11 cm⁶/s and 6.5 x 10^-11 cm⁶/s, and the monomolecular (defect) coefficients are 2.9x10⁷ /s and 5.5x10⁷ /s. Regardless of the analysis used we find that the vast majority, approximately 80%, of the current at threshold is due to the cubic recombination process which is traditionally assumed to be Auger recombination.