Sergey Vyacheslavovich Balakirev

III-V semiconductor nanowires have garnered significant research interest for next-generation micro- and optoelectronic devices, driven by their superior electronic and optical properties and their potential for direct integration on silicon. A central challenge in harnessing this potential is the development of scalable techniques for the deterministic, site-controlled growth of nanowire arrays. This work presents a novel maskless approach for the selective-area formation of GaAs nanowires with controlled position, geometrical and optical characteristics. We investigate the effects of Ga focused ion beam irradiation and pre-growth annealing of Si(111) substrates on subsequent GaAs nanowire growth. For the first time, we demonstrate that the Ga ion dose is the critical parameter governing nanowire nucleation and growth, while the ion beam energy and annealing duration have a negligible impact. We propose a mechanism based on the chemical and structural modification of the native silicon oxide layer during annealing, induced by implanted Ga ions. This dose-dependent modification provides tunable surface conditions are achieved, which dictates the epitaxial growth mode and, hence, the crystal structure and morphology of nanowires. We also propose a novel approach enabling formation of either dense nanowire arrays with high selectivity and vertical yield or precisely positioned single nanowires. The developed ion-beam based technique represents a promising step towards a versatile, maskless lithographic method for the site-controlled synthesis of III-V nanowires on silicon.

This paper presents for the first time the results of studying the influence of annealing modes of GaAs(111) substrates modified by focused ion beams on the transformation of the geometric characteristics of formed nanoholes due to the processes of local droplet etching. Experimental regularities of the influence of the number of ion beam passes, as well as the modes of substrate annealing (in an arsenic flux or its absence) on the shape, depth, and lateral size of nanoholes are established. The mechanism of transformation of the geometric characteristics of nanoholes formed at the points of influence of a focused ion beam during annealing under different modes leading to local droplet etching of the substrate at varying intensities is proposed.

In this paper, for the first time, we report a strong effect of the arsenic pressure used for the high-rate GaAs capping of self-assembled InAs quantum dots on their optical properties. A 140 nm red shift of the photoluminescence peak position is observed when the overgrowth arsenic pressure increases threefold. We explain this behavior in terms of different intensities of quantum dot decomposition, which occurs during the overgrowth under different conditions. When the arsenic pressure is sufficiently high, a GaAs capping layer is formed by deposited species with a low impact on initial quantum dots. At a low arsenic pressure, arsenic deficiency leads to the intensive intermixing caused both by the enhanced Ga/In atom exchange and by the consumption of arsenic atoms belonging to quantum dots for the GaAs capping layer formation. As a result of the overgrowth, quantum dots are divided into families with a large (high pressure) and a small (low pressure) average size, yielding long-wave (1.23 µm) and short-wave (1.09 µm) photoluminescence peaks, respectively. Thus, a significant influence of the overgrowth arsenic pressure on the characteristics of InAs quantum dots is evidenced in this study.

We reveal a novel phenomenon observed after self-catalytic growth of GaAs nanowires (NWs) on Si(111) substrates treated with a Ga focused ion beam (FIB). Depending on the ion dose, NW arrays with various geometrical parameters can be obtained. A minor treatment of the substrate enables a slight increase in the surface density of NWs relative to an unmodified substrate area. As the ion dose is increased up to ∼0.1 pC μm⁻², the growth of GaAs NWs and nanocrystals is suppressed. However, a further increase in the ion dose stimulates the crystal growth leading to the formation of extremely thin NWs (39 ± 5 nm) with a remarkably high surface density of up to 15 μm⁻². Resting upon an analysis of the surface structure before and after stages of ion-beam treatment, ultra-high vacuum annealing and NW growth, we propose a mechanism underlying the phenomenon observed. We assume that the chemical interaction between embedded Ga ions and a native Si oxide layer leads either to the enhancement of the passivation properties of the oxide layer within FIB-modified areas (at low and middle ion doses), or to the etching of the passivating oxide layer by excess Ga atoms, resulting in the formation of pores (at high ion doses). Due to this behavior, local fabrication of GaAs NW arrays with a diverse range of characteristics can be implemented on the same substrate. This approach opens a new way for self-catalytic growth of GaAs NWs.