InAs quantum boxes: Highly efficient radiative traps for light emitting devices on Si

We have compared by photoluminescence (PL) the radiative quantum efficiencies η of an array of InAs/GaAs quantum boxes (QBs) obtained by self-organized growth and of a single high quality InGaAs quantum well (QW). On GaAs substrates, η is essentially the same for both structures. A growth on a commercial GaAs-on-Si substrate entails drastic quenching of the integrated PL intensity and shortening of the carrier lifetime τ for the InGaAs QW, whereas both τ and η are not modified for the QB array. The efficient carrier capture by InAs QBs, combined with the localized nature of QB excitons hinders in this case the carrier diffusion toward dislocations. These superior properties of QBs on Si, which are observed over a wide range of excitation powers and for temperatures up to 300 K, opens a novel route toward efficient and reliable light emitters on Si.