m.g. ganchenkova 1 , v.a. borodin 2 , r. nieminen 1
DESCRIPTION
COSIRES 2004 7th International Conference on Computer Simulation of Radiation Effects in Solids. Annealing of vacancy complexes in P-doped silicon. M.G. Ganchenkova 1 , V.A. Borodin 2 , R. Nieminen 1. 1 COMP/Laboratory of Physics, Helsinki University of Technology, Espoo, Finland - PowerPoint PPT PresentationTRANSCRIPT
M.G. Ganchenkova1, V.A. Borodin2, R. Nieminen1
1COMP/Laboratory of Physics, Helsinki University of Technology, Espoo, Finland
2RRC Kurchatov Institute, Moscow, Russia
Annealing of vacancy complexes in P-doped Annealing of vacancy complexes in P-doped siliconsilicon
COSIRES 2004 7th International Conference on Computer Simulation of Radiation Effects in Solids
June 2004, Helsinki, Finland
PV and VPV and V22 : Experimental data : Experimental data
P.Pellegrino et al., Phys.Rev.B, 64 (2001), 195211
The defects are annealed The defects are annealed outout
PV V2
150 C
250 C
Recombination with highly mobile interstitial type defect
PV – NONO V2 - NONO
Possible reasons:Possible reasons:
Thermal dissociation
PV – YES ?YES ? V2 – NO ?NO ?
Long-range diffusion to sinks
PV – NO ?NO ? V2 – YES ?YES ?
DLTS spectra of n-type Si DLTS spectra of n-type Si samples after isochronal samples after isochronal annealing (30min) between annealing (30min) between 150 and 300 150 and 300 C
June 2004, Helsinki, Finland
Schematic representation of E-
center • Ps acts as a trap for vacancies …
Formation and binding energies for PV complex
a. C.S.Nichols, C.G.Van de Walle and S.T.Pantelides, Phys.Rev.B 40, 8 (1989) 5484b. X.Y.Liu, W.Windle, K.M. Beardmore and M.P.Masqueller, Appl.Phys.Lett 82, 12 (2003), 1839c. R.Virkunnen and R.M.Nieminen, Comp.Mat.Science 1 (1993) 351d. R.Car, P.J.Kelly, A.Oshyama, amd S.T.Pantelides, Phys.Rev.Lett. 54, 4 (1985) 360e. O.Sugino and A.Oshyama, Phys.Rev.B 46 (1992)12335f. P.M.Fahley, P.B.Griffin, and J.D.Plummer, Rev.Mod.Phys. 61 (1989) 1049
P-V complexP-V complex
June 2004, Helsinki, Finland
Ef ,our calc. eV
Ef
other calc. eV
Eb our calc., eV
Eb
other calc., eV
Eb exp., eV
PV+ 2.14 2.4 0.92
PV0
2.31 2.0
2.5a
2.5b 1.02
1.0 a
1.15 b
0.63 c
1.8 d
0.3 e
1.04
f
PV- 2.53 2.8
2.2 b
1.12 1.44
b
PV2- 2.99 1.28
June 2004, Helsinki, Finland
0
0.2
0.4
0.6
0.8
1
1.2
1 2 3 4
coordination sphere
Bin
din
g e
ne
rgy
(e
V)
Binding energy vs. constituent Binding energy vs. constituent separation : PVseparation : PV
Binding energies on coordination spheres Def type 1 2 3 4 5
PV+ 0.92 0.21 0.34 not calc. 0.21
PV0 1.02 0.37 0.26 not calc. 0.24
PV- 1.12 0.49 0.32 not calc. 0.29
PV2- 1.28 0.55 0.38 not calc. 0.35
•PV0, PV- binding energy decreases monotonically with increasing separation
…with a big vacancy capture radius
•PV is a bound system for P - V separations extending to at least three intermediate chemical bonds
Thermal dissociation or … ???Thermal dissociation or … ???
Experiment : … PV centers anneal already at 150 C … Possible reason: thermal dissociation
June 2004, Helsinki, Finland
Dissociation of PV complex - vacancy jumps outside the "three-bond layer"
Dissociation of PV complex - multistage process
Vacancy jumps : 1 NN + 2 NN
3 NN + 4 NN +…
5 NN + …
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 2 4 6 8 10
Coordination sphere
En
erg
y (e
V)
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 2 4 6 8 10
step along the trajectory
En
erg
y (
eV
)Thermal dissociation or … ???Thermal dissociation or … ???
The vacancy return jump is more than 10 times more probable than the jump in the outward direction.
at 150at 150ooC :C :
favorable conditions for P atom mobility
… … annealing on annealing on sinks ???sinks ???
Activation energy sequence for PV complex dissociation
Migration energies for PV complex
NNN
Ex
possible diffusion jumps
L.C.Kimerling: ring mechanism is responsible for annealing of PV centers at 150 C
Limiting reaction of the ring mechanism – direct exchange jump
a. C.S.Nichols, C.G.Van de Walle and S.T.Pantelides, Phys.Rev.B 40, 8 (1989) 5484b. X.Y.Liu, W.Windle, K.M. Beardmore and M.P.Masqueller, Appl.Phys.Lett 82, 12 (2003), 1839
… … annealing annealing on on sinks ???sinks ???
June 2004, Helsinki, Finland
Thermal dissociation or … annealing on Thermal dissociation or … annealing on sinks ??? sinks ???
June 2004, Helsinki, Finland
200 300 400 500 600 70010-310-210-1100101102103104105106107108
Life
time, s
Temperature, oC
PV+
PVo
PV-
PV2-
dissociation times are quite small as compared to typical experiment durations : 30 min
! Main reason – ! Main reason – Thermal Thermal dissociationdissociation
200 300 400 500 600 7000.01
0.1
1
10
100
1000
10000
100000
Jum
ps
per
eve
nt
Temperature, oC
PV +
<> P+ + Vo: V P
PV o <> P+ + V
-: V P
PV - <> P
+ + V2-: V P
PV 2-
<> P+ + V3-: V P
P atom displacement is rather small, except as a part of PV2-
The relative decrease of PV complex concentration The relative decrease of PV complex concentration as a function of time and annealing temperature as a function of time and annealing temperature
PV+ PV0
PV- PV2-
The relative decrease of PV complex concentration The relative decrease of PV complex concentration as a function of time and annealing temperature as a function of time and annealing temperature
PV2- up to 100 s PV2- up to 1000 s
June 2004, Helsinki, Finland
23, 216 SC Г, 216 SC Experiment
(0/+) 0.13 0.04 0.25d
(-/0) 0.41 0.38 ~0.55f 0.78e
(2-/-) 0.51 0.43 0.75d
Ef(V20) 5.54 4.94
23, 216 SC Г, 216 SC Experiment
(+/2+) 0.12 0.19a 0.13b
(0/+) 0.09 0.11a 0.05b
(-/0) 0.27 0.57a -
(2-/-) 0.23 0.40a -
V2+
V20
V2-
V22-
V+
V0
V-
V2-
V2+
Some words about mono- and divacancy Some words about mono- and divacancy in Siin Si
M.J.Puska et al. Phys. Rev. B 58 (1998) 1318; b) G. D. Watkins, in Deep Centers in Semiconductors, edited by S.T. Pantelides (Gordon and Breach, New York, 1986 ), p.147; c)M.Pesola et al. Phys.Rev. 58 (1998) 1106 ; d)G. D. Watkins, J. W. Corbett, Phys. Rev. 138 (1965) A543; f) P.Hauttojärvi et al. , Defect Diffus.Forum 153-155 (1998) 97; e) E.V. Monakhov, A.Yu. Kuznetsov and B.G. Svensson, Phys. Rev. B 63 (2001) 245322
June 2004, Helsinki, Finland
Binding energy vs. constituent Binding energy vs. constituent separation : Vseparation : V22
Two vacancies are strongly bound in the first NN configuration
-1
-0.5
0
0.5
1
1.5
2
2.5
1 2 3 4 5 6
coordination sphere
Bin
din
g e
ner
gy
(eV
)
Binding energies on coordination spheres Def type 1 2 3 4 5
V2+ 1.20 -- 0.2 -0.25 -0.23
V20 1.23 -- -0.71 0.08 -0.30
V2- 1.50 -- -0.21 0.15 0.25
V22- 1.66 -- -0.17 0.28 0.44
the second NN configuration is unstable
The trend of binding energy change with increase of coordination sphere number that defines the mutual arrangement of vacancies in V2
complex
-0.5
0
0.5
1
1.5
2
2.5
0 2 4 6 8
coordination sphere
En
erg
y (e
V)
-0.5
0
0.5
1
1.5
2
2.5
0 2 4 6 8
coordination sphere
En
erg
y (e
V)
… … vacancy jumps directly to the third or fifth NN vacancy jumps directly to the third or fifth NN positionposition
much higher stability of a divacancy as much higher stability of a divacancy as compared to PV compared to PV
June 2004, Helsinki, Finland
The relative decrease of VThe relative decrease of V22 complex concentration complex concentration as a function of time and annealing temperature as a function of time and annealing temperature
V2+ V2
0
V2-
V22-
ConclusionsConclusions
1 . Both PV complex and a divacancy are strongly bound complexes in silicon, but their kinetic behaviour is completely different.
2. Experimentally observed disappearance of PV signal at temperatures ≈ 150oC can be explained in terms of thermal dissociation of PV complex, but only provided this complex is in the doubly negatively charged state.
3. The divacancy in all investigated charge states is found to be very stable against thermal dissociation at experimentally reported temperatures.
4. Specific features of vacancy interaction at small separations completely exclude any reasonable possibility for divacancy migration in the bound state.
June 2004, Helsinki, Finland