Hexagonal silicon grown from higher order silanes

We demonstrate the merits of an unexplored precursor, tetrasilane (Si4H10), as compared todisilane (Si2H6) for the growth of defect-free, epitaxial hexagonal silicon (Si). We investigate thegrowth kinetics of hexagonal Si shells epitaxially around defect-free wurtzite gallium phosphide(GaP) nanowires. Two temperature regimes are identified, representing two different surfacereaction mechanisms for both types of precursors. Growth in the low temperature regime(415 °C–600 °C) is rate limited by interaction between the Si surface and the adsorbates, and inthe high temperature regime (600 °C–735 °C) by chemisorption. The activation energy of the Sishell growth is 2.4 ± 0.2 eV for Si2H6 and 1.5 ± 0.1 eV for Si4H10 in the low temperatureregime. We observe inverse tapering of the Si shells and explain this phenomenon by a basicdiffusion model where the substrate acts as a particle sink. Most importantly, we show that, byusing Si4H10 as a precursor instead of Si2H6, non-tapered Si shells can be grown with at least 50times higher growth rate below 460 °C. The lower growth temperature may help to reduce theincorporation of impurities resulting from the growth of GaP