Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

Abstract

Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMS), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose, and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As, and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (InFe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

Intrinsic magneto-optical spectra of GaMnAs

“…4,14 This blue shift was attributed to the Moss-Burstein effect, in which the Fermi level moves toward lower energy in the valence band as the Mn content x increases; however, this interpretation is inconsistent with the impurity-band conduction picture, which is supported by the recent studies. 2,3,5,[15][16][17][18]21 In particular, this interpretation is inconsistent with the transmission MCD results, 2,3,5 although both of reflection and transmission MCD can be expressed by the same dielectric tensor which is intrinsic to materials. In order to correctly understand the observed MCD spectra, it is important to determine the dielectric tensor of GaMnAs and to derive its intrinsic MCD spectra that are free from the optical interference.…”

“…Our results indicate that the blue shifts of E 0 originate from optical interference and are consistent with the impurity-band conduction picture, in which the Fermi level exists in the band gap even in heavily Mn-doped GaMnAs. 2,3,5,[15][16][17][18]21 Table I summarizes the structural parameters, growth conditions, and properties of the samples examined in this study, which are composed of Ga 1Àx Mn x As (d nm)/GaAs (100 nm) grown on semi-insulating GaAs (001) substrates by low-temperature molecular-beam epitaxy, as illustrated in Fig. 1.…”

Systematic study of electronic and magnetic properties for Cu12–xTMxSb4S13 (TM = Mn, Fe, Co, Ni, and Zn) tetrahedrite

“…[1][2][3][4] Valence states and d-band structures for the TM impurities have attracted as much interest from their technological importance as well as from the viewpoint of basic physics. Particularly, diluted ferromagnetic semiconductors such as In 1Àx Mn x As, 5-8 Ga 1Àx Mn x As, 9,10 and Zn 1Àx Cr x Te 11,12 are expected to be used in spintronics devices.…”

Heat-Treatment-Induced Switching of Magnetic States in the Doped Polar Semiconductor Ge1−xMnxTe

“…GeTe also offers the possibility of enhanced magnetic interactions and applicability in spintronics devices: Magnetism is induced in GeTe when doping with Cr, Mn, or Fe at the Ge site343536373839, forming a family of diluted magnetic semiconductors similar with (GaMn)As or (Ga,Mn)N4041424344. Recently, the possibility of multiferroicity has been claimed in this multifunctional system due to the coexistence of magnetism and ferroelectric distortion45.…”