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