Scanning tunneling microscopy of GaAs/GaAsSb nanowires
Résumé
Understanding surface structure and surface composition is of particular importance for semiconductor nanowire applications, since they might strongly contribute to the electrical, optical and thermal properties of the Nanowires. A prototypical material is GaAs, where polytype inclusions consisting of zinc-blende (ZB) and wurtzite (WZ) segments form during the growth of nanowires, in particular when Sb atoms are incorporated. Here, we will investigate the structural and electronic properties of GaAs and GaAsSb nanowires with scanning tunneling microscopy and spectroscopy. These techniques gives access to the nanofaceting morphology of a single semiconductor nanowire with a detailed picture of the sidewall structural and compositional properties at the atomic scale. It will also be used to measure the band gap and the position of the Fermi level at the surface. In particular, we will show that the ZB_WZ structures on the surface of GaAs nanowires naturally introduce p-i juntions solely due to the Fermi level pinning at different energies on the non-polar WZ and ZB sidewall facets.