Built-in electric field assisted spin injection in Cr and Mn δ-layer doped AlN/GaN(0001) heterostructures from first principles

X. Y. Cui, J. E. Medvedeva, B. Delley, Arthur J Freeman, C. Stampfl

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Highly spin-polarized diluted ferromagnetic semiconductors are expected to be widely used as ideal spin injectors. Here, extensive first-principles density-functional theory calculations have been performed to investigate the feasibility of using Cr- and Mn-doped wurtzite polar AlN/GaN(0001) heterostructures, with the aim to realize the appealing half-metallic character and, hence, efficient electrical spin injection. To overcome the formation of detrimental embedded clusters, we propose digital δ-layer doping perpendicular to the growth direction so as to realize enhanced performance at room temperature. The formation energy, electronic and magnetic properties, and the degree of spin polarization for both neutral and charged valence states for various concentrations are studied. Under both metal-rich (Al- or Ga-rich) and N-rich conditions, Cr and Mn dopants prefer to segregate into the GaN region and reside close to the interface, where dopant incorporation occurs more readily under N-rich conditions. The doped Cr and Mn atoms introduce 3d states in the band gap of the host semiconductor heterostructure. The spin injection channels are constructed via the hybridization between dopant 3d and surrounding host atoms, up to a few monolayers around the interface, where the spin-polarized t2 electrons are injected into AlN without the conductivity mismatch problem. Significantly, for the energetically favorable configurations, the built-in electric field in the AlN/GaN(0001) heterointerface serves as a driving force for efficient spin injection through the interface and spin transport in the AlN region. Also importantly, the electronic properties of the heterostructures (half metallic, semiconducting, or metallic) are found to depend sensitively upon the doping concentration and valence charge states. In general, charged valence states can destroy the ferromagnetic half metallicity for both systems, particularly in n -type materials. These results will be useful with regard to the practical fabrication of desirable heterostructures for optoelectronic and semiconductor spintronic devices.

Original languageEnglish
Article number245317
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume78
Issue number24
DOIs
Publication statusPublished - Dec 1 2008

Fingerprint

Heterojunctions
Electric fields
Doping (additives)
injection
electric fields
Semiconductor materials
Electronic properties
Atoms
valence
Magnetoelectronics
Spin polarization
Optoelectronic devices
Density functional theory
Monolayers
Magnetic properties
Energy gap
Metals
energy of formation
Fabrication
semiconductor devices

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Built-in electric field assisted spin injection in Cr and Mn δ-layer doped AlN/GaN(0001) heterostructures from first principles. / Cui, X. Y.; Medvedeva, J. E.; Delley, B.; Freeman, Arthur J; Stampfl, C.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 78, No. 24, 245317, 01.12.2008.

Research output: Contribution to journalArticle

@article{46a10fc934b24d458158d92c480f0c16,
title = "Built-in electric field assisted spin injection in Cr and Mn δ-layer doped AlN/GaN(0001) heterostructures from first principles",
abstract = "Highly spin-polarized diluted ferromagnetic semiconductors are expected to be widely used as ideal spin injectors. Here, extensive first-principles density-functional theory calculations have been performed to investigate the feasibility of using Cr- and Mn-doped wurtzite polar AlN/GaN(0001) heterostructures, with the aim to realize the appealing half-metallic character and, hence, efficient electrical spin injection. To overcome the formation of detrimental embedded clusters, we propose digital δ-layer doping perpendicular to the growth direction so as to realize enhanced performance at room temperature. The formation energy, electronic and magnetic properties, and the degree of spin polarization for both neutral and charged valence states for various concentrations are studied. Under both metal-rich (Al- or Ga-rich) and N-rich conditions, Cr and Mn dopants prefer to segregate into the GaN region and reside close to the interface, where dopant incorporation occurs more readily under N-rich conditions. The doped Cr and Mn atoms introduce 3d states in the band gap of the host semiconductor heterostructure. The spin injection channels are constructed via the hybridization between dopant 3d and surrounding host atoms, up to a few monolayers around the interface, where the spin-polarized t2 electrons are injected into AlN without the conductivity mismatch problem. Significantly, for the energetically favorable configurations, the built-in electric field in the AlN/GaN(0001) heterointerface serves as a driving force for efficient spin injection through the interface and spin transport in the AlN region. Also importantly, the electronic properties of the heterostructures (half metallic, semiconducting, or metallic) are found to depend sensitively upon the doping concentration and valence charge states. In general, charged valence states can destroy the ferromagnetic half metallicity for both systems, particularly in n -type materials. These results will be useful with regard to the practical fabrication of desirable heterostructures for optoelectronic and semiconductor spintronic devices.",
author = "Cui, {X. Y.} and Medvedeva, {J. E.} and B. Delley and Freeman, {Arthur J} and C. Stampfl",
year = "2008",
month = "12",
day = "1",
doi = "10.1103/PhysRevB.78.245317",
language = "English",
volume = "78",
journal = "Physical Review B-Condensed Matter",
issn = "1098-0121",
publisher = "American Physical Society",
number = "24",

}

TY - JOUR

T1 - Built-in electric field assisted spin injection in Cr and Mn δ-layer doped AlN/GaN(0001) heterostructures from first principles

AU - Cui, X. Y.

AU - Medvedeva, J. E.

AU - Delley, B.

AU - Freeman, Arthur J

AU - Stampfl, C.

PY - 2008/12/1

Y1 - 2008/12/1

N2 - Highly spin-polarized diluted ferromagnetic semiconductors are expected to be widely used as ideal spin injectors. Here, extensive first-principles density-functional theory calculations have been performed to investigate the feasibility of using Cr- and Mn-doped wurtzite polar AlN/GaN(0001) heterostructures, with the aim to realize the appealing half-metallic character and, hence, efficient electrical spin injection. To overcome the formation of detrimental embedded clusters, we propose digital δ-layer doping perpendicular to the growth direction so as to realize enhanced performance at room temperature. The formation energy, electronic and magnetic properties, and the degree of spin polarization for both neutral and charged valence states for various concentrations are studied. Under both metal-rich (Al- or Ga-rich) and N-rich conditions, Cr and Mn dopants prefer to segregate into the GaN region and reside close to the interface, where dopant incorporation occurs more readily under N-rich conditions. The doped Cr and Mn atoms introduce 3d states in the band gap of the host semiconductor heterostructure. The spin injection channels are constructed via the hybridization between dopant 3d and surrounding host atoms, up to a few monolayers around the interface, where the spin-polarized t2 electrons are injected into AlN without the conductivity mismatch problem. Significantly, for the energetically favorable configurations, the built-in electric field in the AlN/GaN(0001) heterointerface serves as a driving force for efficient spin injection through the interface and spin transport in the AlN region. Also importantly, the electronic properties of the heterostructures (half metallic, semiconducting, or metallic) are found to depend sensitively upon the doping concentration and valence charge states. In general, charged valence states can destroy the ferromagnetic half metallicity for both systems, particularly in n -type materials. These results will be useful with regard to the practical fabrication of desirable heterostructures for optoelectronic and semiconductor spintronic devices.

AB - Highly spin-polarized diluted ferromagnetic semiconductors are expected to be widely used as ideal spin injectors. Here, extensive first-principles density-functional theory calculations have been performed to investigate the feasibility of using Cr- and Mn-doped wurtzite polar AlN/GaN(0001) heterostructures, with the aim to realize the appealing half-metallic character and, hence, efficient electrical spin injection. To overcome the formation of detrimental embedded clusters, we propose digital δ-layer doping perpendicular to the growth direction so as to realize enhanced performance at room temperature. The formation energy, electronic and magnetic properties, and the degree of spin polarization for both neutral and charged valence states for various concentrations are studied. Under both metal-rich (Al- or Ga-rich) and N-rich conditions, Cr and Mn dopants prefer to segregate into the GaN region and reside close to the interface, where dopant incorporation occurs more readily under N-rich conditions. The doped Cr and Mn atoms introduce 3d states in the band gap of the host semiconductor heterostructure. The spin injection channels are constructed via the hybridization between dopant 3d and surrounding host atoms, up to a few monolayers around the interface, where the spin-polarized t2 electrons are injected into AlN without the conductivity mismatch problem. Significantly, for the energetically favorable configurations, the built-in electric field in the AlN/GaN(0001) heterointerface serves as a driving force for efficient spin injection through the interface and spin transport in the AlN region. Also importantly, the electronic properties of the heterostructures (half metallic, semiconducting, or metallic) are found to depend sensitively upon the doping concentration and valence charge states. In general, charged valence states can destroy the ferromagnetic half metallicity for both systems, particularly in n -type materials. These results will be useful with regard to the practical fabrication of desirable heterostructures for optoelectronic and semiconductor spintronic devices.

UR - http://www.scopus.com/inward/record.url?scp=58149458023&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=58149458023&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.78.245317

DO - 10.1103/PhysRevB.78.245317

M3 - Article

VL - 78

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 24

M1 - 245317

ER -