Stable and high yield growth of GaP and In0.2Ga0.8As nanowire arrays using In as a catalyst

Autor: Andrea Scaccabarozzi, Andrea Cattoni, Frank Glas, Fabrice Oehler, Jean-Christophe Harmand, Gilles Patriarche, Stéphane Collin, Laurent Travers
Přispěvatelé: Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Rok vydání: 2020
Předmět:
Zdroj: Nanoscale
Nanoscale, Royal Society of Chemistry, 2020, 12 (35), pp.18240-18248. ⟨10.1039/d0nr04139d⟩
ISSN: 2040-3372
2040-3364
Popis: International audience; We report the first investigation of indium (In) as the vapor-liquid-solid catalyst of GaP and GaAs nanowires by molecular beam epitaxy. A strong asymmetry in the Ga distribution between the liquid and solid phases allows one to obtain pure GaP and In 0.2 Ga 0.8 As nanowires while the liquid catalyst remains nearly pure In. This uncommon In catalyst presents several advantages. First, the nanowire morphology can be tuned by changing the In flux alone, independently of the Ga and group V fluxes. Second, the nanowire crystal structure always remains cubic during steady state growth and catalyst crystallization, despite the low contact angle of the liquid droplet measured after growth (95 •). Third, the vertical yield of In-catalyzed GaP and (InGa)As nanowires arrays on patterned silicon substrates increases dramatically. Combining straight sidewalls, controllable morphologies and a high vertical yield, In-catalysts provide an alternative to the standard Au or Ga alloys for the bottom-up growth of large scale homogeneous arrays of (InGa)As or GaP nanowires. We note that the SET and NT curves nearly coincide over all 78 the explored composition range. This typical of NW growth and 79 was already observed by Glas on [Ga]-(AlGa)As NWs 34. It relates 80 to the low concentration of group V in the liquid catalyst, as com-81 puted using SET (see Supplementary Information †) or deduced 82 from other experiments 36. 83 From both NT and SET, we find that the Ga distribution is 84 strongly asymmetric. This particular Ga distribution is not unique 85 to our system and similar curves were calculated for ternary 86 [Au]-(InGa)As NWs using NT 25. These fast changes in the solid 87 (x) at near constant liquid composition (y) are often hindering 88 the fabrication of NW with uniform composition. Yet, away from 89 these abrupt changes, the solid composition varies slowly over 90 large ranges of liquid composition. Most relevant to the present 91 work, Ga contents (x) in solid In 1−x Ga x P and In 1−x Ga x As reach 92 near unity while the Ga fractions (y) in the liquid remain below 93 a few atomic percents. Hence the VLS growth of nearly pure GaP 94 and GaAs NWs from nearly pure In catalyst seems achievable. 95 3 Steady state growth 96 In light of the above calculations, we have proceeded to grow 97 [In]-(InGa)P and [In]-(InGa)As NWs on patterned Si(111) sub-98 strates using MBE (see experimental). Both In and Ga atoms are 99 supplied continuously to sustain the NW growth so that In evap-100 oration is compensated and the catalyst composition remains In-101 rich. Compared to [Ga]-GaAs or [Ga]-GaP NWs, typically grown 102 at 600 • C 15,36 , the substrate temperature is reduced to 520 • C to 103 limit the evaporation of In adatoms. Identical Si(111) wafers with 104 hexagonal arrays (300 nm pitch) of 50 nm diameter holes in a 105 14 nm thick silica mask are used to grow selectively the GaAs and 106 GaP NWs. The details of the growth and patterning procedures 107 can be found in the experimental section.
Databáze: OpenAIRE
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