Hole confinement in quantum islands in Ga (AsSb) GaAs (AlGa) As heterostructures

Formation of self-organized Ga(AsSb) quantum islands during growth is shown to occur in a series of Ga (AsSb) GaAs (AlGa) As heterostructures, resulting in an in-plane hole confinement of several hundred meV. The shape of the in-plane confinement potential is nearly parabolic and, thus, yields almost equidistant hole energy levels. Transmission electron microscopy reveals that the quantum islands are 100 nm in diameter and exhibit an in-plane variation of the Sb concentration of more than 30%. Up to seven bound hole states are observed in the photoluminescence spectra. Time-resolved photoluminescence data are shown as function of excitation density, lattice temperature, and excitation photon energy and reveal fast carrier capture into, and relaxation within, the quantum islands. The advantages of such structures as active laser material are discussed.