VERY-LOW SATURATION DENSITIES IN STRAINED INGAAS ALGAAS MULTIPLE-QUANTUM WELLS

The saturation of excitonic absorption in strained InGaAs/AlGaAs quant um wells is systematically measured as a function of strain. By compar ison 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 s aturation densities, as low as 0.82X10(17) CM-3, are reported for the InGaAs/AlGaAs quantum wells with an indium concentration of 15%. The r eduction in the saturation density is attributed to the change in the valence band density of states and the fact that these samples were de signed to be fully strained. A novel method of measuring the absorptio n without antireflection coatings is described.