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Shape, Size Evolution, and Nucleation Mechanisms of GaAs Nanoislands Grown on (111)Si by Low-Temperature Metal–Organic Vapor-Phase Epitaxy

  • Ilio Miccoli
    Ilio Miccoli
    Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, I-73100 Lecce, Italy
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  • Paola Prete*
    Paola Prete
    Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche, SS Lecce, Via Monteroni, I-73100 Lecce, Italy
    *P.P.: e-mail, [email protected]; tel, +39 0832 297 250; fax, +39 0832 297 249.
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  • , and 
  • Nico Lovergine
    Nico Lovergine
    Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Via Monteroni, I-73100 Lecce, Italy
Cite this: Cryst. Growth Des. 2019, 19, 10, 5523–5530
Publication Date (Web):August 13, 2019
https://doi.org/10.1021/acs.cgd.9b00225
Copyright © 2019 American Chemical Society

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    Abstract

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    The shape, size evolution, and nucleation mechanisms of GaAs nanoislands grown at 400 °C on As-stabilized (111)Si by metal–organic vapor phase epitaxy are reported for the first time. GaAs crystallizes in the zincblende phase in the very early nucleation stages until a continuous epilayer is formed. GaAs nanoislands grow (111)-oriented on Si as truncated hexagonal pyramids, bound by six equivalent {120} side facets and a (111) facet at the top. Their diameter and height appear to increase linearly with the deposition time, yielding a constant aspect ratio of ∼1/4. The nanoisland density (before coalescence) stays constant with time at ∼2 × 1010 cm–2, suggesting that the nucleation occurs at specific Si surface sites (defects) during the very early growth stages, rather than being due to the continuous formation of new nuclei. To understand the molecular-level mechanisms driving the low-temperature MOVPE growth of GaAs on Si, we applied a deposition–diffusion–aggregation (DDA) nucleation model, which predicts a linear evolution of the overall GaAs growth rate with surface coverage, in good agreement with experimental observations, under the assumption that direct impingement of trimethylgallium (Me3Ga) molecules onto the nanoisland surface dominates the material nucleation and growth rate; the contribution of Me3Ga adsorbed onto the As-stabilized (111)Si is negligible, pointing out the reduced reactivity of the Si surface (As passivation). Our DDA model allows estimation of the effective reactive sticking coefficient of Me3Ga onto GaAs, which is equal to 2.82 × 10–5: the small value is compatible with the Me3Ga large steric hindrance and the competitive role of methyl radicals in surface adsorption at low temperature.

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    Cited By

    This article is cited by 2 publications.

    1. Santhanu Panikar Ramanandan, Joel Reñé Sapera, Alban Morelle, Sara Martí-Sánchez, Alok Rudra, Jordi Arbiol, Vladimir G. Dubrovskii, Anna Fontcuberta i Morral. Control of Ge island coalescence for the formation of nanowires on silicon. Nanoscale Horizons 2024, 9 (4) , 555-565. https://doi.org/10.1039/D3NH00573A
    2. Nico Lovergine, Ilio Miccoli, Leander Tapfer, Paola Prete. GaAs hetero-epitaxial layers grown by MOVPE on exactly-oriented and off-cut (1 1 1)Si: Lattice tilt, mosaicity and defects content. Applied Surface Science 2023, 634 , 157627. https://doi.org/10.1016/j.apsusc.2023.157627