Nonradiative centers in InAs quantum dots revealed by two-wavelength excited photoluminescence

Abstract

We studied nonradiative recombination centers in MBE-grown InAs/GaAs quantum dot (QD) structures with photoluminescence (PL) peak energies between 1.12 and 1.29 eV by the scheme of two-wavelength excitation. Temporally chopped below-gap excitation (BGE) light of 0.75 eV was superposed on a CW above-gap excitation light of 1.59 eV on the sample surface, and the resultant PL intensity change due to the BGE (BGE effect) was measured. Observed 25–35% decrease in PL intensity at 80–90 K implies a first discrimination of a pair of nonradiative centers activated at 0.75 eV inside the band gap of the QD region. Due to trap-filling, the BGE effect showed saturation with increasing BGE power. Its temperature dependence below 50 K was different from that of quantum wells, reflecting carrier dynamics peculiar to the QD.