GaAs:Mn Nanowires Grown by Molecular Beam Epitaxy of (Ga,Mn)As at MnAs Segregation Conditions

Abstract

ABSTRACT:GaAs:Mn nanowires were obtained on GaAs(001) and GaAs(111)B substrates by molecular beam epitaxial growth of (Ga,Mn)As at conditions leading to MnAs phase separation. Their density is proportional to the density of catalyzing MnAs nanoislands, which can be controlled by the Mn flux and/or the substrate temperature. After deposition corresponding to a 200 nm thick (Ga,Mn)As layer the nanowires are around 700 nm long. Their shapes are tapered, with typical diameters around 30 nm at the base and 7 nm at the tip. The wires grow along the <111> direction, i.e. along the surface normal on GaAs(111)B and inclined on GaAs(001). In the latter case they tend to form branches. Being rooted in the ferromagnetic semiconductor (Ga,Mn)As, the nanowires combine one-dimensional properties with the magnetic properties of (Ga,Mn)As and provide natural, self assembled structures for nanospintronics.

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

“…Although the growth of monocrystalline GaMnAs layers using a high Mn flux is impossible at high temperatures, 11 1-D nanowire (NW) growth at a Mn/Ga flux ratio of several percent is possible, which has been demonstrated in several studies. [11][12][13][14] Although some studies have shown room temperature ferromagnetism, 14,15 the origin and mechanism of the reported magnetization are not clear.…”

“…[11][12][13][14] Although some studies have shown room temperature ferromagnetism, 14,15 the origin and mechanism of the reported magnetization are not clear. For example, the formation of ferromagnetic precipitates or clusters such as MnAs should be considered as a possible source of magnetism.…”

“…For example, the formation of ferromagnetic precipitates or clusters such as MnAs should be considered as a possible source of magnetism. 11,16,17 Recently, core-shell structured NWs consisting of GaAs/GaMnAs, 18 GaAs/MnAs, 19,20 and InGaAs/GaMnAs 21 have been considered as well. 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.…”

“…11,16,17 Recently, core-shell structured NWs consisting of GaAs/GaMnAs, 18 GaAs/MnAs, 19,20 and InGaAs/GaMnAs 21 have been considered as well. 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.…”

Ferromagnetic GaAs/GaMnAs Core−Shell Nanowires Grown by Molecular Beam Epitaxy

“…We note that in previous studies the growth of GaMnAs nanowires under typical NW, i.e., high temperature conditions, has been reported. [28][29][30] Sadowski et al 29 showed that the growth of GaMnAs at MnAs segregation conditions led to the formation of MnAs nanocluster acting as catalyst for the NW growth. The obtained NWs were strongly tapered with side branches.…”