Structural and optical properties of self-catalytic GaAs:Mn nanowires grown by molecular beam epitaxy on silicon substrates

Abstract

Mn-doped GaAs nanowires were grown in the self-catalytic growth mode on the oxidized Si(100) surface by molecular beam epitaxy and characterized by scanning and transmission electron microscopy, Raman scattering, photoluminescence, cathodoluminescence, and electron transport measurements. The transmission electron microscopy studies evidenced the substantial accumulation of Mn inside the catalyzing Ga droplets on the top of the nanowires. Optical and transport measurements revealed that the limit of the Mn content for self-catalysed growth of GaAs nanowires corresponds to the doping level, i.e., it is much lower than the Mn/Ga flux ratio (about 3%) used during the MBE growth. The resistivity measurements of individual nanowires confirmed that they are conductive, in accordance with the photoluminescence measurements which showed the presence of Mn(2+) acceptors located at Ga sites of the GaAs host lattice of the nanowires. An anomalous temperature dependence of the photoluminescence related to excitons was demonstrated for Mn-doped GaAs nanowires.

All-Wurtzite (In,Ga)As-(Ga,Mn)As Core–Shell Nanowires Grown by Molecular Beam Epitaxy

“…The LO mode is indeed frequently observed in GaAs NWs under these conditions. 21 Therefore, the absence of the GaAs-like, (In,Ga)As LO mode in Raman spectra further confirms the outstanding quality of the cores of the investigated NWs.…”

“…GaAs NWs grow best at high temperatures (550 °C -650 °C), thus first we have investigated the Mn doping limits of GaAs NWs grown in this high temperature range. 21 We have observed that Mn doesn't deteriorate the growth of GaAs NWs, even with quite high Mn/Ga flux ratio of about 3%. We have found that at high growth temperatures, Mn can be introduced into GaAs NWs only at doping levels (below 10 18 cm -3 ).…”

“…We have found that at high growth temperatures, Mn can be introduced into GaAs NWs only at doping levels (below 10 18 cm -3 ). 21 Such nanowires grow well in <111> preferential crystal directions, revealing hexagonal cross-section with a catalyst droplet on the top. 21 It is well known that Mn solubility limits in the GaAs lattice can be overcome at non equilibrium growth conditions using low growth temperature (LT-MBE).…”

“…21 Such nanowires grow well in <111> preferential crystal directions, revealing hexagonal cross-section with a catalyst droplet on the top. 21 It is well known that Mn solubility limits in the GaAs lattice can be overcome at non equilibrium growth conditions using low growth temperature (LT-MBE). 1 Therefore, previously we have also investigated the growth of NWs at low temperatures (about 350 °C) only slightly higher than those typically applied for MBE growth of (Ga,Mn)As layers.…”

Direct observation of doping incorporation pathways in self-catalytic GaMnAs nanowires

“…Some of these studies showed that low temperature grown GaMnAs shells can contain high Mn concentrations up to $5% and have ferromagnetic phase transitions above 20 K. 18,21 We have demonstrated previously 11,13 that it is possible to grow GaMnAs NWs by MBE at low temperatures (300-350 C) and if the growth temperature is slightly too high, the formation of MnAs nanoclusters occurs on the surface. However, due to high disorder in terms of NW orientation, crystallographic defects, and morphology, other growth regimes of Mn-doped GaAs NWs have been exploited: (i) Ga catalyzed NWs grown at high temperature on Si(100), 13 (ii) Ga catalyzed NWs grown at high temperature on Si(111), 22 and (iii) low-temperature grown GaMnAs shells on high-temperature grown Au-catalyzed GaAs NWs on GaAs(111)B. 21 In this paper, we focus on investigating in details structural and compositional properties of Mn-doped Ga catalyzed GaAs NWs grown on Si(111) at high a)…”