Over 100 ns intrinsic radiative recombination lifetime in type II InAs/GaAs1−xSbx quantum dots

Abstract

We report very long intrinsic radiative recombination lifetime τrad in type II InAs quantum dots embedded in GaAs1−xSbx. The dependence of photoluminescence (PL) decay time τPL on both the Sb composition (x = 0–0.18) and excitation intensity (38–460 mW/cm2) was systematically investigated by time-resolved PL measurements with a time-correlated single-photon counting method. All PL decay curves exhibited non-exponential profiles, and τPL was strongly dependent on the excitation intensity. These properties were well explained by solving rate equations of carrier density with neglecting nonradiative process, in which τrad is inversely proportional to carrier density. The 18% Sb sample exhibited a τPL of over 100 ns under weak excitation, which is longer than twice the previously reported values. We evaluated the value of τrad in InAs/GaAs1−xSbx QDs relative to that in type I InAs/GaAs QDs based on an effective mass approximation and found that the observed extremely long τPL corresponds to τrad.