Complex emission dynamics from InGaAs/GaAs core-shell nanopillars

In this work, the optical properties and emission dynamics of core-shell InGaAs/GaAs nanopillars (NPs) have been in- vestigated using low-temperature photoluminescence (PL) and time-resolved photoluminescence (TRPL). These novel structures have recently attracted much interest within the silicon photonics scientific community due to their potential employment as gain medium for monolithically integrated lasers on silicon substrates. The optimization of the emission properties of these heterostructures is essential to obtain full compatibility with silicon photonics and requires an accurate tailoring of the pillar geometry (i.e. size, pitch) and composition. Therefore it is critical to gain deeper insight into the optical and dynamical properties of different NP designs if optimal device performance is to be achieved. The experimental characterization, carried out on a number of different NP structures with different geometries and compositions, shows that the time evolution of the emission peak exhibits a strong excitation-dependent blue-shift which can be attributed to the band-filling effect. Measured emission decay times were strongly geometry-dependent and varied from nanoseconds to tens of picoseconds. In addition, a dramatic reduction of the decay time was observed for the highest indium concentration due to the dominant contribution of the strain-induced non-radiative recombination processes.