1. 전이금속이 포함된 GaN의 전자구조 및 자기적 특성해석
30회 학술대회, 광운대학교
전이금속이 포함된 GaN의 전자구조 및 자기적 특성해석
이승철, 이광렬
한국과학기술연구원 미래기술연구본부

2. Spintronics Control of Spin and Charge of Electrons Simultaneously
Magnetic Tunneling Junction
Spin Field Effect Transistor
Spin dependent tunneling
Magnetic RAM
Semiconductor based device
Next generation of spintronics
D. Awschalom et al, Scientific American (2002)

3. Models for Ferromagnetism DMS
Localized magnetic moment surrounded by non-local carrier
Impurity induces a polarization in the host
(RKKY type interaction) TM
Induced hole
Multiple impurities trapped by few carriers
(percolation of magnetic polarons)

4. Success 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 Mn
Ku et al., APL (2003)

5. Total DOS and Mn d state*10
GaMnAs
Total DOS and Mn d state*10
As state

6. T. Dietl, Semicond. Sci. Technol. 17 (2002) 377
DMSs beyond Ga1-xMnxAs
T. Dietl, Semicond. Sci. Technol. 17 (2002) 377

7. Requirements for DMS Materials
The carriers (holes) are polarized and DMS can serve as efficient sources for spin injection.
Because Curie temperature is correlated with the carrier concentration, the magnetic order can be manipulated with voltage.

8. Models for Ferromagnetism in Ga1-xMnxAs
Localized magnetic moment surrounded by non-local carrier
Impurity induces a polarization in the host
(RKKY type interaction) TM
Induced hole
Multiple impurities trapped by few carriers
(percolation of magnetic polarons)

9. Research Results Related to GaN:TM
GaN:Mn
Most of the studies based on GaN host has focused on this system.
Short range interaction of Mn.
Self interaction of electrons might be important in this system.
GaN:Cr
This system is based on the prediction of Sato et al.
Almost all the studies have focused on the magnetic interaction between transition metal ion.

10. First Principle Calculation
Density Functional Theory
Kohn-Sham Eq. ( Single Electron Schrodinger Equation)
Results Obtained from the Kohn-Sham Equation
Cohesive energy
Charge density
Electronic structure (band, DOS)
Nature of bonding
STM image simulation
Etc

11. Calculation Condition
Planewave Pseudopotential Method: VASP
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

12. Structure of 64-Atom GaN Transition Metal 5th Nitrogen 1st NN Nitrogen
3rd NN Nitrogen
2nd NN Nitrogen

13. 3d Transition Metals

14. Mn doped GaAs and GaN
GaMnAs
GaMnN

15. Partial DOSs having less-than half filled d state
GaVN
GaCrN
GaMnN
GaN:Mn(7)
Up Spin
Up Spin
Up Spin
Down Spin
t2g eg

16. Partial DOSs having more-than half filled d state
GaFeN
GaCoN
GaCuN
GaNiN

17. No Splitting of Valence p-band
Electron Occupation in GaN
No Splitting of Valence p-band
GaN:Mn(7)
GaN:Co(9)
Up Spin
Up Spin
Up Spin
Down Spin
Up Spin
Up Spin
Up Spin
Down Spin
t2g eg
GaN:Ni(10)
GaN:Cu(11)
Up Spin
Up Spin
Up Spin
Down Spin
Up Spin
Up Spin
Up Spin
Down Spin
Filled Electron
Unfilled Electron

18. Magnetic Moments of Nitrogen

19. Half filled d electrons of TM
Total and TM Local Magnetic Moments
Half filled d electrons of TM
3+ valency
2+ valency

20. Interaction Range of TM
V, Cr, Mn
Fe, Co, Ni, Cu

21. 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.