Optical characterization of selectively intermixed GaAs/GaAlAs quantum wires by Ga+ masked implantation

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Abstract
Quantum wires were fabricated by selective intermixing of a GaAs/GaAlAs quantum well through masked Ga+ implantation and rapid thermal annealing. The evolution of the luminescence spectra of the wires with the width of the implantation masks, enabled us to characterize the lateral selectivity of our process as well as the degree of one‐dimensional confinement. The lateral extent of the intermixing was estimated at 20 nm giving rise to an important penetration of aluminum into the wires. From numerical simulations of the spatial distribution of implantation‐induced damage, it was concluded that some lateral diffusion of the defects occurred during annealing. However it has been possible to assess the confinement energies to be around 4 meV. The linewidth of the wires’ emission turned out to increase with decreasing mask size, indicating the presence of some fluctuations of the confining potential along the wires. The roughness of the lateral definition of the wires was evaluated at 20 nm, of the same order of magnitude as the dimension of the intermixed region under the mask. Under these conditions optical excitation spectroscopy failed to detect the different one‐dimensional subbands. Finally the potentialities of this method of fabrication of quantum wires are inspected.