Growth of antimony-containing heterostructure nanowires by molecular beam epitaxy : crystal phase control, surfaces and interfaces
Résumé
Growth of III-V nanowires has now gained some maturity and fundamental understanding of the growth mechanisms has dramatically progressed. However, there are only three families of III-Vs which have been extensively explored: nitrides, arsenides and phosphides. The growth and understanding of binary or ternary antimonides is only emerging now. The main motivation for developing antimonide nanowires is to link the intrinsic advantages of the nanowire geometry (possibility to relax strain very efficiently without creation of dislocations, quantum confinement, control of crystal phase), with the exceptional bulk properties of these semiconductors, such as small bandgaps, huge electron (InSb) or hole (GaSb) mobilities, the largest Landé g factor (InSb), a high thermoelectric figure of merit (InSb) and vast possibilities of bandstructure engineering, both in type I or type II/III alignments.Here we present advanced nanowire structures containing antimony and grown by molecular beam epitaxy. Structural characteristics are analyzed using scanning electron microscopy, transmission electron microscopy, and scanning tunneling microscopy. Nanowire heterostructures have been grown by a vapour-liquid-solid mechanism, using either gold seed particles or a gold-free “self-catalyzed” approach. We report the achievement, for the first time, of InSb nanowires by molecular beam epitaxy. We then show ternary GaAs/GaAsxSb1-x, InAs/InAsxSb1-x abrupt nanowire heterostructures, of controlled composition. It is demonstrated that crystal structure of ternary nanowires can be tuned with high control from defected to perfect phases, by inclusion of just a few atomic percent of antimony. Due to an overgrowth process, both wurtzite and zinc-blende InAsSb sidewall facets occur, and are revealed by low temperature STM with atomic resolution.