Carrier recombination rates in GaAs and InGaAs quantum-well lasers

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The carrier recombination rates in GaAs1 and strained InGaAs/GaAs single-quantumwell lasers have been studied using the differential carrier-lifetime technique for carrier densities from 1017-1019/cm3. We have found that the carrier lifetime is not an intrinsic property of the material but is strongly structure-dependent. Under high levels of excitation, the recombination rates deviate considerably from the recombination rules of the bulk materials. The rates are typically smaller in quantum wells that have lower potential barriers and/or thinner well widths. The rates increase sublinearly with increasing carrier density up to carrier densities of approximately 1017/cm3 (rather than super-linearly as is observed in the bulk), but they remain nearly constant for densities greater than 1019/cm3. This occurs because a portion of the injected carriers populate the continuum states of the confinement layers where the carrier volume density is diluted and the overall carrier lifetime is prolonged. These inactive carriers may lead to the anomalously large linewidth enhancement factor in some InGaAs/GaAs lasers. Our experimental work also demonstrates that Auger recombination is negligible in GaAs and strained InGaAs/GaAs single quantum wells for carrier densities on the order of 1019/cm3.