Epitaxial integration of the highly spin-polarized ferromagnetic semiconductor EuO with silicon and GaN

Abstract

Doped EuO is an attractive material for the fabrication of proof-of-concept spintronic devices. Yet for decades its use has been hindered by its instability in air and the difficulty of preparing and patterning high-quality thin films. Here, we establish EuO as the pre-eminent material for the direct integration of a carrier-concentration-matched half-metal with the long-spin-lifetime semiconductors silicon and GaN, using methods that transcend these difficulties. Andreev reflection measurements reveal that the spin polarization in doped epitaxial EuO films exceeds 90%, demonstrating that EuO is a half-metal even when highly doped. Furthermore, EuO is epitaxially integrated with silicon and GaN. These results demonstrate the high potential of EuO for spintronic devices.

Antiferromagnetic coupling in EuO1−x

“…9 Recent studies of spin-resolved x-ray absorption spectroscopy have shown a spin-split conduction band of about 0.6 eV in its ferromagnetic state, creating a nearly 100% spin polarized electrons close to the conduction band edge. 10 Although the stoichiometric EuO has a Curie temperature (Tc) of 69 K, Tc can be enhanced significantly by pressure, [11][12][13] interfacial strain 14 or electron doping via rare-earth atoms [15][16][17][18][19][20][21][22][23][24] or oxygen vacancies. 15,16,[23][24][25] The integrations of EuO with Si, 18,[23][24][25][26][27] GaAs, 28 and GaN 18 have been successfully demonstrated.…”

Microscopic theory for a ferromagnetic nanowire/superconductor heterostructure: Transport, fluctuations, and topological superconductivity

“…[1][2][3][4] A particularly attractive candidate ferromagnetic semiconductor is europium oxide (EuO), which is known to possess nearly spin-polarized bands. 85,86 EuO becomes ferromagnetic below 70K under ambient pressure and the Curie temperature is known to increase with pressure reaching 200K under 1.5 × 10 5 atmospheres. 87 Since its integration with with Si and GaN, 86 EuO has garnered much attention for its potential use in spintronic applications.…”

“…85,86 EuO becomes ferromagnetic below 70K under ambient pressure and the Curie temperature is known to increase with pressure reaching 200K under 1.5 × 10 5 atmospheres. 87 Since its integration with with Si and GaN, 86 EuO has garnered much attention for its potential use in spintronic applications. Ferromagnetic superconductors are materials that exhibit intrinsic coexistence of superconductivity and ferromagnetism where the same electrons are believed to be superconducting and ferromagnetic simultaneously.…”

Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

“…Recently it was shown, that EuO can be epitaxially grown on Si and GaN, which opens new possibilities for device realization. 4,43 …”

“…Current interest in EuX magnetic semiconductors arises from potential applications for spintronics and magneto-optical devices. 4,5 Their nonlinear optical and magneto-optical properties, however, remained unexplored until recently when magnetic-field-induced second-harmonic generation ͑SHG͒ was observed in EuTe, EuSe, 6,7 and in EuO. 8 Nonlinear optics is a large, continuously expanding field of fundamental and applied research.…”