STRUCTURAL CHARACTERIZATION OF (IN,GA)AS QUANTUM DOTS IN A GAAS MATRIX

Morphology evolution of molecular-beam-epitaxy-grown InAs and In0.5Ga0.5As layers as a function of deposition thickness, range from 1 to 10 ML, is studied by transmission-electron microscopy to characterize the formation and the self-organization of pseudomorphic quantum dots. For deposition (at 450-480°C) of 3-7 ML of InAs and 5-10 ML of InxGa1-xAs, respectively, well-developed and crystallographically perfect dots with typical base length of 12 nm and small size dispersion form, which exhibit short-range ordering on a primitive two-dimensional square lattice along 100. The luminescence from all samples with coherent dots exhibits high quantum efficiency. For 4-ML InAs dots, coincidence of luminescence and absorption is demonstrated. Arrangement of InxGa1-xAs dots in chains along [110] is the result of ordering during deposition at even lower temperatures (∼320°C). © 1995 The American Physical Society.