Optical transition pathways in type-II Ga(As)Sb quantum dots

We present results of room temperature photoreflectance (PR) and photoluminescence (PL) measurements of molecular-beam epitaxy (MBE)-grown GaAsSb/GaAs quantum dot structures: one with an In0.14Ga0.86As capping quantum well and one without it. PL was used to determine the structures' ground-state transition energies. This result was employed in an 8-band k·p Hamiltonian to achieve a band structure of the structures, which have different electron confinement. The dot emission energies suggest a large amount of As incorporation into the dots, which is due to enhanced adatom mixing at a higher than normal growth temperature of 510 °C. Our calculations indicate a dot composition of 25-50% Sb gives the best fit to experiment. This uncertainty in composition arises due to the fact that different bowing parameters of the ternary alloy could be applied in the calculations. The theoretical analysis accounts well for the main feature in the PR spectra of both samples.