Temperature dependence of the photoluminescence spectra from InAs(P)/InP multilayers containing thick quantum dots: Dot-size-dependent carrier dynamics

摘要

We have studied the temperature dependence (~ 10-293 K) of the photoluminescence (PL) from In As/InP(001) quantum dot (QD) multilayers with thin spacer layers (~5 nm) emitting in the 0.6-0.8 eV spectral region. The QD emission redshifts less than the InAs bulk material band gap with increasing temperature. This behavior is accompanied by an important rise of the relative PL intensity of the higher-energy contributions to the spectra. The room-temperature emission is rather strong—over 20% of the low-temperature value—since deep confinement effects prevent the thermal escape of the carriers out of these relatively large QD's. In addition, the carrier transfer from the wetting layers to the QD's increases with the number of layers at low temperatures. A dot-size-dependent analysis of the carrier dynamics using a rate-equation model leads to the following interpretation of our experimental results: (i) the radiative emission intensity from thicker dots quenches at lower temperature through thermalization to excited nearly dark states, and (ii) carriers initially captured by the wetting layer are preferentially transferred to thinner QD's whose emission energy is higher than ~0.7 eV. In multilayers, the experimental observations can be explained without involving electronic coupling between QD's of different layers, even though the distance between the vertically aligned nanostructures is small.