The role of the confinement potential symmetry on the electronic and optical properties of quantum wires is systematically studied. In a wide class of quantum wires with mirror symmetry we evidence a new set of optical transitions resulting both from band mixing and C2v symmetry breaking at zone center. Several kinds of quasi-one-dimensional excitons are predicted as well as their specific dipole coupling. Even for ultralow C1 symmetry we find independent excitons with distinct polarization selection rules.

The structure of AlGaAs vertical quantum well (VQW) structures grown by low-pressure organometallic chemical vapor deposition on V-grooved GaAs substrates was analyzed as a function of growth temperature and Al mole fraction using transmission electron microscopy and atomic force microscopy (AFM). The low-pressure growth yields several, extremely narrow (a few nm wide) branches of Ga-enriched VQWs at the bottom of the grooves. The variation in Al content across the VQW was evaluated by measuring the AlGaAs oxide thickness on a cleaved edge of the structure using AFM in air. The transmission electron microscopy analysis demonstrates that the different VQW branches originate from distinct nanofacets that self-order at the bottom of the V-groove, probably due to facet-induced segregation of group III species.

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We have observed selective carrier injection into GaAs/AlGaAs V-groove quantum wires (QWRs) via self-ordered vertical quantum wells (VQWs). Room-temperature I–V characteristics of QWR diodes show a turn-on voltage lower by 0.2 V as compared with planar QW diodes, consistent with the band-gap reduction of 0.2 eV at the vertical QW. This selective injection results in narrow linewidth electroluminescence (∼5 nm at 300 K) emanating exclusively from the QWR from 10 K up to 300 K.

We have investigated the transition from nonresonant to resonant coupling between quantum confined one-dimensional carriers and two-dimensional photon states in a wavelength-long planar Bragg microcavity incorporating strained In 0.15 Ga 0.85 As/GaAs V-groove quantum wires ͑QWRs͒. Clear spectral and angular redistribution of the broad ͑8 meV͒ and weakly directional QWR emission in free space into the narrow ͑1 meV͒ and directional resonant quasimodes of the planar microcavity is observed, resulting in an intense ͑ϫ50͒ and polarization controlled emission from the microcavity QWRs. Moreover, the microcavity confinement is used to discriminate between QWR excitons with different degrees of localization, and to alter exciton diffusion both in real and k space.͓S0163-1829͑99͒51012-6͔ RAPID COMMUNICATIONS PHYSICAL REVIEW B 15 MARCH 1999-II VOLUME 59, NUMBER 12 PRB 59 0163-1829/99/59͑12͒/7809͑4͒/$15.00 R7809