Structural characterization of (In,Ga)As quantum dots in a GaAs matrix

Abstract

Morphology evolution of molecular-beam-epitaxy-grown InAs and ${\mathrm{In}}_{0.5}$ ${\mathrm{Ga}}_{0.5}$As 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 ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As, 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 ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As dots in chains along [110] is the result of ordering during deposition at even lower temperatures (∼320 °C).