Temperature Dependent Absorption and Emission Enhancement Factors in Plasmon Coupled Semiconductor Heterostructures

摘要

Localized surface plasmon resonances can increase the quantum efficiency of photon emitters through bothabsorption and spontaneous emission enhancement effects. Despite extensive studies, experimental results thatclearly distinguish the two plasmonic enhancement effects are rarely available. Here, we present clear spectralsignatures of the plasmonic enhancement effects on the absorption (excitation) and spontaneous emission(Purcell factor) by analyzing the temperature dependent photoluminescence (PL) properties of InGaAs/GaAssingle quantum well (QW) coupled to colloidal gold nanorods (AuNRs) at different GaAs capping layerthickness (d). We find that when the emitting InGaAs layer is close to the AuNRs (d = 5 nm), the plasmonicenhancement effect on the QW PL is dominated by the Purcell factor that significantly increases the externalquantum efficiency of the QW that otherwise barely emits. When d is increased to 10 nm, the temperaturedependence of the PL enhancement factor (F) reflects absorption enhancement in the capping layer followedby carrier diffusion and capture by the well. First F increases with temperature and then decreases followingthe temperature dependence of the carrier diffusion coefficient in GaAs. By factoring out the contribution ofthe captured carriers to F, it is shown that carrier transfer to the well reaches saturation with increasingincident laser power. In addition to providing insight into the plasmonic enhancement mechanism, the resultspresented in this work suggest that colloidal plasmonic nanoparticles can be used as simple probes forunderstanding carrier transport phenomena in arbitrary semiconductor heterostructures.