Disorder and spectral broadening of vertically stacked InGaAs/GaAs V-grooved quantum wires have been investigated by means of microprobe luminescence. We show that the main spectral broadening mechanism originates from monolayer fluctuations at the bottom of the wire. A direct evidence of monolayer height islands of area $40\times 40\mathrm{nm}$ formed at the bottom of the grooves is provided by atomic force microscopy. Lateral and vertical wire-to-wire fluctuations are found to be negligible on the micron scale.

• Received 19 February 1998

DOI:https://doi.org/10.1103/PhysRevB.58.1962