Extended Data Fig. 1: Schematic illustration of the nanowire growth process.
From: Direct-bandgap emission from hexagonal Ge and SiGe alloys
a, The core nanowire growth starts with a GaAs (111)B substrate patterned with Au catalyst seeds, which is introduced in the MOVPE reactor and annealed at a temperature higher than the eutectic temperature forming an alloy between the catalyst seed and the substrate. b, Next, the GaAs gas precursors (TMGa and AsH3) are introduced, and Au-catalysed GaAs core nanowires are grown. To proceed with the SiGe shell growth, Au seeds are chemically etched away from the GaAs cores and the surface of the cores is repaired (c), and the sample is reintroduced to the MOVPE reactor (d). A hex-Si1 − xGex shell is epitaxially grown around the GaAs cores from precursors (Si2H6 and GeH4). (The molecules are drawn with the freely available MolView Software (http://www.molview.org/)). The 30° tilted scanning electron microscopy images in the bottom panels of a–d are representative of the results of the growth steps in the top panels, with insets in b and c displaying a magnified image of the nanowire. e, A 30° tilted-overview representative scanning electron microscopy image of hex-Ge/GaAs Core shells corresponding to what is shown in Fig. 2, confirming the uniformity of the growth across the sample.
