Very low saturation densities in strained InGaAs/AlGaAs multiple quantum wells

Abstract

The saturation of excitonic absorption in strained InGaAs/AlGaAs quantum wells is systematically measured as a function of strain. By comparison with an unstrained GaAs/AlGaAs quantum well sample a reduction by a factor of up to 9 in the saturation carrier density is observed in strained samples with indium concentrations of 10% and 15%. Very low saturation densities, as low as 0.82×1017 cm−3, are reported for the InGaAs/AlGaAs quantum wells with an indium concentration of 15%. The reduction in the saturation density is attributed to the change in the valence band density of states and the fact that these samples were designed to be fully strained. A novel method of measuring the absorption without antireflection coatings is described.