GaAsSb/InAs core-shell nanowires grown by molecular-beam epitaxy

In this paper, we report for the first time the growth of GaAsSb/InAs core-shell nanowires (NWs) on Si (111) substrates by molecular-beam epitaxy. We first grow high-quality GaAsSb NWs as cores using self-catalyzed technique, then cover these cores by InAs shells. For the growth of InAs shells, we find that the optimum beam equivalent pressure ratio of As/In is only ∼5.2, but the growth temperature window is larger (from 460 to 540 °C). Also, the thickness of InAs shells increases almost linearly with extending the growth time. Because of the high-quality of GaAsSb cores, the InAs shells are continuous, smooth, and without stacking faults or twins adopted from the cores. Temperature dependent I-V curves measured from the field-effect transistor devices based on these GaAsSb/InAs core-shell NWs indicate that GaAsSb/InAs NWs without any intentional doping are electrically conductive. The growth of GaAsSb/InAs core-shell NWs opens up new possibilities for both fundamental studies and future device applications based on such natural p-n junctions.