Self-catalyzed GaAs nanowire growth on Si-treated GaAs(100) substrates

Self-catalyzed GaAs nanowire growth was obtained by molecular beam epitaxy on GaAs(001)substrates after predeposition of subnanometer-thick Si layers. Two substrate preparation methodsare presented, the first based on the epitaxial growth of Si on GaAs and subsequent exposure toatmosphere, and the second on the direct deposition of Si on epiready GaAs substrates. X-rayphotoemission spectroscopy shows that both methods result in a thin Si oxide layer that promotesthe growth of GaAs nanowires aligned along the h111i direction. High densities of nanowires wereobtained at substrate temperatures between 620 and 680 C. Systematic electron microscopystudies indicate that nanowire growth is associated with the formation of Ga nanoparticles onthe substrate surface, which act as a catalyst in the vapor-liquid-solid growth mechanism frame.The majority of the nanowires have a pure zinc-blende structure, and their photoluminescenceis dominated by a photoluminescence peak 3 to 5 meV in width and centered at 1.516 to 1517 eV.