Optical spectroscopy of self-organized nanoscale hetero-structures involving high-index surfaces

Abstract

Similar effects are responsible for self-organization of periodically corrugated surface structures and ordered dot arrays on crystal surfaces. Strain relaxation on facet edges may result in the appearance of periodically corrugated surfaces for lattice-matched growth. Strain relaxation on facet edges and island interaction via the strained substrate act as driving forces for the formation of ordered arrays of uniform, strained lattice-mismatched islands on a crystal surface. A pseudoperiodic square lattice is manifested for the InAs-GaAs(100) system. Less ordered dots are formed on the GaAs(100) surface with a 4 monolayer GaSb deposition. New experimental methods are applied for the characterization of faceted nanoscale structures. For GaAs-AlAs multilayer structures grown on (311)A substrates, interface corrugation results in optical anisotropy of the same sign as expected from the low symmetry growth direction, making the main origin of the anisotropy unclear. Our quantitative optical reflectance and reflectance anisotropy studies show that the interface corrugation plays an important role for thin (less than 4 nm) GaAs layers. Mesa arrays from samples with InAs quantum dots grown on (100) surface are fabricated. The photoluminescence intensity is found to depend only weakly on the mesa size (1000 nm to 250 nm). The estimated electron-hole pair capture time into the InAs dot at room temperature is less than 1 ps. We also found a weak dependence of the threshold current density on the deep mesa stripe width (down to 3 μm) in the case of room temperature operated quantum dot injection lasers.