elemental defect processes in radiation-induced displacement damage in si
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Elemental Defect Processes in Radiation-Induced Displacement Damage in Si. Matthew J. Beck 1 , R. Hatcher 1 , L. Tsetseris 1 , M. Caussanel 2 , R.D. Schrimpf 2 , D.M. Fleetwood 2,1 , and S. T. Pantelides 1 1 Department of Physics and Astronomy - PowerPoint PPT PresentationTRANSCRIPT
Elemental Defect Processes in Radiation-Induced Displacement
Damage in Si Matthew J. Beck1, R. Hatcher1, L. Tsetseris1, M.
Caussanel2, R.D. Schrimpf2, D.M. Fleetwood2,1, and S. T. Pantelides1
1Department of Physics and Astronomy2Department of Electrical Engineering and Computer Science
Vanderbilt University, Nashville, TN 37235 USA
2006 MURI Review – June 13, 2006
Support: DoD, AFOSR
Matthew J. Beck
MURI Review, June 2006
Non-Ionizing Energy Loss (NIEL)
Dale, et al. IEEE Trans. Nucl. Sci., v. 35 p. 1208
(1988).
Matthew J. Beck
MURI Review, June 2006
Experimental Results: Low-NIEL Irradiation
p- and n-Si divergence?
(1965)
(1965)(1965)
G.P. Summers, et al., 1993.
Dec
reas
e in
Min
ority
C
arrie
r Diff
usio
n Le
ngth
Matthew J. Beck
MURI Review, June 2006
Low-NIEL Displacement Damage
NIEL
Low-NIEL
Srour, Marshall and Marshall. IEEE Trans. Nucl. Sci., v. 50 p. 653
(2003).
Matthew J. Beck
MURI Review, June 2006
Displacement Damage
Vacancy + Interstitial = Frenkel Pair (FP)
Matthew J. Beck
MURI Review, June 2006
Introduction: First Principles and Frenkel Pairs
• Frenkel Pairs (FPs) are…– Atomic scale, materials specific– Require atoms AND electrons (e.g. Jahn-Teller effects)– Can be modeled in “small” cell (~216 atoms)
• First Principles methods are…– Atomic scale– Highly accurate for atoms AND electrons– Materials specific– BUT… limited to SMALL systems
Matthew J. Beck
MURI Review, June 2006
Method Details• Parameter-free DFT-LDA calculations
• Ultrasoft pseudopotentials
• Periodic boundary conditions
Matthew J. Beck
MURI Review, June 2006
Results: Equilibrium Properties
yx xz yz
Hexagonal
Tetragonal
+
Interstitial
VacancyApproximate
band of metastable FPs
5.4 Å
Matthew J. Beck
MURI Review, June 2006
Results: Electronic Structure
Valence Band
Conduction Band
Vacancy
Interstitial (~Tet)Frenkel Pair
0.38 nm
V0d2d I0
tet
Matthew J. Beck
MURI Review, June 2006
Results: Charge State Dependent Stability
Valence Band
Conduction Band
Fermi level
p-doped: FP+ is more
stable
Fermi level pinning by n- or p- type doping
n-doped: FP- is less
stable
Matthew J. Beck
MURI Review, June 2006
Analysis: Low-NIEL Defect Profiles
defectsn
Larger defect complexes, requiring large displacements
Effective defect “size”, or Displacement energy required to produce defect
Stable, Isolated FPs
p-Si
Intrinsic Si
n-Si
⇒ Opposite trend to experiments!
Matthew J. Beck
MURI Review, June 2006
Analysis: Frenkel Pair “Capture, Recombine, and Release” Mechanism
Stable FP in Si plus Conduction Band electron
Destabilized FP after electron
capture
Defect-less Si plus Conduction Band electron
FP
e-Si
Removal of excess electron carriersparticipating in this mechanism is delayed!
⇒ Measured excess carrier lifetimes are increased!
Matthew J. Beck
MURI Review, June 2006
Analysis: Effect of Increasing NIEL
defectsn
Increasing NIEL:
Effective defect “size”, or Energy required to produce defect
Larger defect complexes
Isolated FPs
Matthew J. Beck
MURI Review, June 2006
Summary of Relevent Results:n- vs. p-type Behavior
• Significantly more small, isolated Frenkel Pairs are expected in p-type Si than n-type Si.
• Electron capture destabilizes these Frenkel Pairs, delaying the permanent removal of these minority carriers in p-Si.
• For higher NIEL irradiations, the magnitude of this effect becomes insignificant
Matthew J. Beck
MURI Review, June 2006
Conclusions
• Low-NIEL irradiations: p-Si and n-Si divergence.
• Increasing NIEL: difference disappears.
Dec
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e in
Min
ority
C
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ngth
Matthew J. Beck
MURI Review, June 2006
Conclusions and Future Work• Elemental defect processes directly control
larger-scale material and device behavior• First Principles calculations can reveal the
rich physics associated with fundamental defects
• Future Work:– Separation/Recombination Dynamics – Electronic Structure => Internal Charge transfer– Experimental Validation of Mechanism
Matthew J. Beck
MURI Review, June 2006
Experimental SetupAdapted Open Circuit Voltage Decay measurements for carrier lifetimes
Elemental Defect Processes in Radiation-Induced Displacement
Damage in Si Matthew J. Beck1, R. Hatcher1, L. Tsetseris1, M.
Caussanel2, R.D. Schrimpf2, D.M. Fleetwood2,1, and S. T. Pantelides1
1Department of Physics and Astronomy2Department of Electrical Engineering and Computer Science
Vanderbilt University, Nashville, TN 37235 USA
2006 MURI Review – June 13, 2006
Support: DoD, AFOSR