Quaternary (Ga,Mn)BiAs ferromagnetic semiconductor -MBE growth, structural and magnetic properties
|Janusz Sadowski 1,2, Jaroslaw Domagala 2, Aloyzas Šiušys 2, Oksana Yastrubchak 3, Luikasz Gluba 3, Miroslaw Kulik 3, Michal Rawski 3, Maciej Sawicki 2|
1. Lund University, MAX-lab, Lund SE-221 00, Sweden
(Ga,Mn)As ternary alloy is a canonical ferromagnetic semiconductor (FMS) studied for almost two decades by a number of research groups. After over15 years of extensive research activity (Ga,Mn)As became a prototype FMS used in the context of basic research of fundamental properties of FMS materials as well for the construction of novel spintronic devices using the new functionalities associated with the spin orientation of the charge carriers . In spite of that, some basic issues concerning the mechanisms responsible for the FM phase transition in (Ga,Mn)As are still being debated [2,3]. Hence studying quaternary alloy whose band structure is modified by the introduction of an additional V-group element is highly interesting. So far, to our knowledge, only quaternary alloys of this kind reported in the literatures are (Ga,Mn)AsP  and (Ga,Mn)AsSb . Thus we have investigated (Ga,Mn)As alloyed with another V element, namely Bi. It is well known that Bi partially replacing As in GaAs considerably shifts the position of the valence band maximum in the resulting ternary alloy. On the other hand for the FM properties of (Ga,Mn)As (and other Mn-doped FMS materials) the position of Mn acceptor level is detrimental. This feature can be effectively tuned in (Ga,Mn)AsBi by choosing the appropriate Bi content in the quaternary alloy. (Ga,Mn)AsBi layers with the Bi content of up to 1% have been grown on GaAs(001) substrates by molecular beam epitaxy (MBE) at low substrate temperature (200 - 230 oC). In each case the MBE growth of a quaternary alloy was followed by the growth of the ternary (Ga,Mn)As layer with the same Mn content, at nominally identical growth conditions. Thus the influence of Bi on basic characteristics of FMS layers such as Curie temperature, lattice parameter can be investigated. The essential parameters of quaternary (Ga,Mn)BiAs layers, as mentioned above, are investigated by the standard techniques such as SQUID magnetometry and X-ray diffraction. The other features like electronic properties and defect structure are studied by photoreflectivity, transmission electron microscopy and Rutheford backscattering techniques. Our first investigations of magnetic properties of (Ga,Mn)BiAs have shown that Bi considerably changes the magnetic anisotropy of a quternary alloy, with respect to that of ternary (Ga,Mn)As. The origin of this effect will be discussed.
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Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 2, by Janusz Sadowski
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17
Submitted: 2013-03-27 11:05 Revised: 2013-04-15 21:04
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