Available online at http://www.idealibrary.com on doi:10.1006/spmi.2000.0895 Superlattices and Microstructures, Vol. 29, No. 5, 2001 Magnetic field dependence of the binding energy of shallow donors in GaAs quantum-well wires ECATERINA NICULESCU † ,ALINA GEARBA,GABRIELA CONE , C. NEGUTU Department of Physics, ‘Politechnica’ University of Bucharest, 313 Splaiul Independentei, RO-77206, Bucharest, Romania (Received 13 December 1999) Using a variational procedure within the effective-mass approximation we have calculated the binding energies of shallow-donor impurities in cylindrical GaAs quantum-well wires, in an axial magnetic field and an infinite confinement potential. In contrast to the previous results in quantum wells, we have found that, in the magnetic field, the impurity binding energy may be increased or decreased as a function of the impurity location in the quantum wire. On the basis of analysis of the variation of the binding energy with magnetic field strength, a method is proposed for experimentalists to confirm the presence of a shallow donor in the vicinity of the wire boundary. c  2001 Academic Press Key words: quantum wire, shallow donor, binding energy. 1. Introduction With the recent improvements in microfabrication technology of nanostructures the growth of semicon- ductor systems with reduced dimensionality has been actively pursued in recent years. Among the various systems under current investigation, the quantum-well wires (QWWs) have attained considerable theoretical and experimental attention. Due to significant modification in the density of states, improved laser and high- speed device performance using QWWs as the active region has been predicted [1, 2]. The understanding of the electronic and optical properties of impurities in these systems is a subject of scientific interest due to the possible technological applications in optoelectronics. GaAs–(Ga, Al)As QWWs are the most inves- tigated systems, and a number of studies [3–8] concerned with impurity energy levels have been reported in the literature. Latgé et al. [3] have calculated the ground and lowest excited states of a donor impurity in a cylindrical wire. Hiruma et al. [4] have reported the photoluminescence measurement of GaAs quantum-wire microcrystals grown by organometallic vapour-phase epitaxy. Spectral features dominated by free-carrier to acceptor-impurity recombination were attributed to the presence of carbon acceptors in the QWW. The theo- retical calculation by Oliveira et al. [5] of the photoluminescence spectra associated with transitions between the n = 1 conduction-subband state and the acceptor ground state for an infinite-barrier cylindrical GaAs QWW are in good agreement with the experimental results. However, there are relatively few quantitative studies on QWWs in the presence of an external applied field. Montes et al. [6] have studied the action of an external electric field on the binding energy of the † E-mail: 0749–6036/01/050319 + 10 $35.00/0 c  2001 Academic Press