Optimising the defect filter layer design for III/V QDs on Si for integrated laser applications

We introduce the concept of using strained superlattice structures as defect filters, with their purpose to reduce the upwards propagation of dislocations that result from the lattice mismatch which occurs when III-V materials are grown on silicon substrates. Three samples with defect filter layers are grown on Si with and without in situ annealing and are compared to a similar structure grown on a GaAs substrate. Transmission electron microscopy is used to verify the effectiveness of the different designs grown on Si, with the twice-Annealed sample reducing the number of defects present in the active region by 99.9%. Optical studies carried out exhibit brighter room temperature emission and reduced photoluminescence quenching with temperature in samples where annealing is performed. Photoluminescence excitation measurements reveal a ∼20 meV redshift in the position of the GaAs exciton for the samples grown on Si compared to that of GaAs, indicating a residual inplane tensile strain ∼0.35% in the GaAs of the active region for the samples grown on Si.