Self-catalyst growth and characterization of wurtzite GaAs/InAs core/shell nanowires

Abstract

Research on nanowire (NW) growth of III-V semiconductors including GaAs and InAs demonstrated the ability to grow in both wurtzite (WZ) and zincblende (ZB) polymorphs. However, the control of crystal phase in self-catalyzed NW growth is still a remaining challenge. In this study we report a controlled growth of GaAs/InAs core/shell nanowires in WZ phase using self-catalyzed molecular beam epitaxy (MBE). The GaAs NWs having pure WZ crystal were achieved and attributed to the effect of small wetting angle, which is realized by supplying high V/III ratio. Furthermore, the WZ formation is shown to be uninfluenced by NW diameter. For the wetting angle larger than 90°, mixed phase starts to be observed. The InAs shell is planarly grown on six m-plane facets of the GaAs core NWs leading to the same strain states along a and c axes of growth plane, in which tensile and compressive strains are observed for GaAs core and InAs shell, respectively. High-resolution transmission electron microscopy (HR-TEM) reveals a few misfit dislocations (~0.03 nm−1) at GaAs/InAs interface indicating insignificant strain relief via creating misfit dislocation. Electrical characterization of the hetero-wires shows that the InAs shell exhibits n-type conduction. A room-temperature sheet carrier concentration at zero gate-bias of 2.5 × 1012 cm−2 and the corresponding carrier mobility of ~ 900 cm2 V−1 s−1 are demonstrated.