Husky 3300 공기 구동식 다이어프램 펌프 · 125psi(0.86MPa, 8.6bar) 최대 작동 압력, 알루미늄 센터 섹션이 포함된 알루미늄 또는 스테인리스강
전이금속이 포함된 GaN 의 전자구조 및 자기적 특성해석
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Transcript of 전이금속이 포함된 GaN 의 전자구조 및 자기적 특성해석
SpintronicsSpintronics
D. Awschalom et al, Scientific American (2002)
Magnetic Tunneling Junction Spin Field Effect Transistor
• Spin dependent tunneling• Magnetic RAM
• Semiconductor based device• Next generation of spintronics
Control of Spin and Charge of Electrons Simultaneously
Models for Ferromagnetism DMSModels for Ferromagnetism DMS
• Multiple impurities trapped by few carriers
(percolation of magnetic polarons)
• Impurity induces a polarization in the host
(RKKY type interaction)
Localized magnetic moment surrounded by non-local carrier
TM
Induced hole
Success and Failure of Ga1-xMnxAsSuccess and Failure of Ga1-xMnxAs
• Mn substitutes Ga in zincblende structure– Structure is compatible
with GaAs 2DEG
• Tc is correlated with carrier density
• Ferromagnetic semiconductor with ordering temperature ~ 160 K
Ku et al., APL 82 2302 (2003)
Mn
Requirements for DMS MaterialsRequirements for DMS Materials
1. The carriers (holes) are polarized and DMS can serve as efficient sources for spin injection.
2. Because Curie temperature is correlated with the carrier concentration, the magnetic order can be manipulated with voltage.
Models for Ferromagnetism in Ga1-
xMnxAsModels for Ferromagnetism in Ga1-
xMnxAs
• Multiple impurities trapped by few carriers(percolation of magnetic polarons)
• Impurity induces a polarization in the host(RKKY type interaction)
Localized magnetic moment surrounded by non-local carrier
TM
Induced hole
Research Results Related to GaN:TMResearch Results Related to GaN:TM
1. GaN:Mn• Most of the studies based on GaN host has focused o
n this system.• Short range interaction of Mn.• Self interaction of electrons might be important in this
system.
2. GaN:Cr• This system is based on the prediction of Sato et al.
3. Almost all the studies have focused on the magnetic interaction between transition metal ion.
First Principle CalculationFirst Principle Calculation• Density Functional Theory• Kohn-Sham Eq. ( Single Electron Schrodinger Equation)
KS KS KSeffH E
• Results Obtained from the Kohn-Sham Equation– Cohesive energy– Charge density– Electronic structure (band, DOS)– Nature of bonding– STM image simulation– Etc
Planewave Pseudopotential Method: VASP.4.6.21 XC functional: GGA(PW91) Cutoff energy of Planewave: 800 eV 4X4X4 k point mesh with MP Electronic Relaxation: Davidson followed by RMM-DIIS Structure Relaxation: Conjugate Gradient Force Convergence Criterion: 0.01 eV/A Gaussian Smearing with 0.1 eV for lm-DOS Treatment of Ga 3d state
Semicore treatment for GaN Core treatment for GaAs
Calculation ConditionCalculation Condition
Transition Metal
1st NN Nitrogen 4th Nitrogen
2nd NN Nitrogen 3rd NN Nitrogen
Structure of 64-Atom GaNStructure of 64-Atom GaN
5th Nitrogen
GaCrNGaVN
Partial DOSs having less-than half filled d state
GaMnN
Up Spin Down SpinUp SpinUp Spin
t2g
eg
GaN:Mn(7)
Up Spin Down SpinUp SpinUp Spin
t2g
eg
Filled Electron Unfilled Electron
Up Spin Down SpinUp SpinUp Spin
GaN:Mn(7) GaN:Co(9)
Up Spin Down SpinUp SpinUp Spin
GaN:Ni(10)
Up Spin Down SpinUp SpinUp Spin
GaN:Cu(11)
Electron Occupation in GaNElectron Occupation in GaNNo
Splitting of Valence p-
band
Magnetic Moments of Nitrogen
1st N 2nd N 3rd N 4th N-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
Ma
gn
etic
Mo
me
nt (
/ato
m)
Cu Ni Co Fe Mn Cr V GaAs:Mn
Summary• Electronic and magnetic properties of transition metal doped GaN was
studied using first principle calculation.• Valence band splitting was observed in the cases of Fe, Co, Ni, and Cu,
which have more-than-half-filled character.• Cu doped GaN was predicted as the most probable candidates for DMS
material.• Further studies on magnetic interaction should be followed to confirm
the prediction.