Magneto-luminescence study of quantum wire arrays in (Al,Ga)As serpentine superlattice structures

Abstract

(Al,Ga)As serpentine superlattices (SSLs) with a built-in quantum wire array have been grown on vicinal GaAs substrates by molecular beam epitaxy. The geometric size of the parabolic-crescent cross section of the quantum wires is on the order of 160 Å × 50 Å, depending on the angle of the vicinal substrate and the amount of parabolic curvature. The low-temperature magneto-luminescence properties of these quantum wire arrays have been studied in magnetic fields up to 13 T. The diamagnetic shift from the serpentine structure was found to be smaller than from a reference alloy-well sample, indicating an increased binding energy of the exciton due to the lateral confinement in the serpentine structure. A diamagnetic shift anisotropy is observed when the magnetic field is applied in the three principal perpendicular directions of the wire. In particular we see a difference when the magnetic field is applied parallel to the the wire and perpendicular to the wire, in qualitative agreement with theoretical calculations. This is a direct observation of the one-dimensional properties of the excitonic wave function. The linewidth is found to increase with the applied magnetic field, with the amount of the increase critically dependent on the direction of the magnetic field. This is explained by the way the exciton volume is probing the potential variations in the ordered SSL structure.