Near-field low-temperature photoluminescence spectroscopy of single V-shaped quantum wires

We report on a near-field spectroscopic study of single V-shaped ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ quantum wires. With subwavelength resolution, the emission from single ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ wires and connecting planar quantum wells—separated by 250 nm—are individually resolved. The contributions of both monolayer height fluctuations on a 100 nm length scale and of short range compositional disorder to the localization of excitons in V-shaped quantum wires are separately identified and their implications for far-field PL spectra discussed. An upper limit for the migration length of the photogenerated excitons within the GaAs barrier layers of 250 nm is determined.