Hexagonal silicon grown from higher order silanes

摘要

We demonstrate the merits of an unexplored precursor, tetrasilane (Si4H10), as compared to disilane (Si2H6) for the growth of defect-free, epitaxial hexagonal silicon (Si). We investigate the growth kinetics of hexagonal Si shells epitaxially around defect-free wurtzite gallium phosphide (GaP) nanowires. Two temperature regimes are identified, representing two different surface reaction mechanisms for both types of precursors. Growth in the low temperature regime (415 degrees C-600 degrees C) is rate limited by interaction between the Si surface and the adsorbates, and in the high temperature regime (600 degrees C-735 degrees C) by chemisorption. The activation energy of the Si shell growth is 2.4 +/- 0.2 eV for Si2H6 and 1.5 +/- 0.1 eV for Si(4)H(10 )in the low temperature regime. We observe inverse tapering of the Si shells and explain this phenomenon by a basic diffusion model where the substrate acts as a particle sink. Most importantly, we show that, by using Si4H10 as a precursor instead of Si2H6, non-tapered Si shells can be grown with at least 50 times higher growth rate below 460 degrees C. The lower growth temperature may help to reduce the incorporation of impurities resulting from the growth of GaP.