Irradiation Induced Diffusion in Semiconductors
Irradiation Induced Diffusion in Semiconductors Recombination Enhanced Diffusion in Semiconductors H.J.von Bardeleben Institut des NanoSciences de Paris (INSP) CNRS/Université Paris 6 140, rue de Lourmel, 75015 Paris
Outline I Introduction Si: the case of the monovacancy and interstitial Ge: recombination enhanced annealing of Frenkel pairs C: the interstitial case (R2) GaN: carrier induced annealing II Electron irradiated n-type GaAs the interstitial mobility /the Frenkel pair annealing III Models for recombination enhanced diffusion: Energy release model (Lang, Kimmerling) Bourgoin mecanism (Bourgoin, Corbett) IV Application of RED: Regeneration of degraded solar cells IV Conclusions
Irradiation enhanced diffusion Different types of irradiations Electron: close to threshold- correlated Frenkel pairs Proton: transmitted energy – isolated vacancy interstitial pairs Ions: cascade defects
Atomic collisions displacement of atoms Electronic excitation: free carrier generation Recombination via defects –enhanced diffusion
Enhanced diffusion mecansims
Field enhanced: charge state related Defect enhanced: interstitial formation and diffusion – kick off of substitutional impurites Al, B in Si Recombination enhanced : energy release mechanism Bourgoin mecanism saddle point changes
and Defect modification: degrade or regenerate degraded devices J.C.Bourgoin,J.W.Corbett, Radiation effects 36,157(1978)
Field enhanced
Coulomb interactions Between charged defects
Defect enhanced
Defect complexes PSi, VSi-PSi (E center)
Ionization enhanced
D(charge state) Sii (0/+/2+)in Si
Sii + AlSi → SiSi+Ali Lattice atoms Drift under applied fields (DLTS/ Ge)
SiC: Ci (C-C)C Unstable at 200°C
RED athermal diffusion Energy release mec. Bourgoin mecansim
Recombination enhanced diffusion
Intrinsic defects: Vacancies Interstitials Frenkel pairs
And Impurities: Ali in Si
Some examples:
Si the case of the vacancy and interstitial Ge Frenkel pair (in)stability under recombination C: the carbon interstitial -R2 defect GaN :the Ga nterstitials (L5,L6)
GaAs: Frenkel pair distribution modifications
Si: the thermal stability and carrier induced mobility of the Monovacancy e- irradiation of Si at low T: VSi-Sii VSi (EPR), Sii invisible, Sii related defects (EPR,LVM)
REM 4K
REM 4.2K
monovacancy
Thermal stability n-type 70K p-type 150K si 200K
G.D.Watkins, Materials Science in Semiconductor Processing 3,227 (2000)
Recombination Enhanced Diffusion in p-type Si (EPR, DLTS)
Observation of the Mono-Vacancy athermal diffusion at 4K…20K under 1.165eV photoexcitation
1 jump /40photons
low energy 350keV e- irradiation 1 jump / 103 recombinations Observation of the Ev+0.17eV level (Ali) under 1.165eV at 320K
A.P.Chatterjee et al,(1983) PhD thesis J.R.Troxel et al
Thermal stability 500K
Why is the Si interstitial so mobile in p-type Si
Low barrier for diffusion in Si+ Bourgoin mecanism between 0/2+ charge states
Annealing of e- induced defects in n-type Ge Electron irradiation: T=10K, E=1MeV creates acceptor defects Ec-60meV Defects analyzed by electrical measurements (DLTS, resistivity)
Thermal annealing : 1 stage at 69K Model: V-I recombination
Under 1.6µm light excitation: 1 stage at 27K
V.Emtsev, Materials Science in Semiconductor Processing 9,580(2006)
Low energy irradiation induced annealing in n-type Ge 1. e- 1 MeV defect generation 2. e- 500keV defect annealing at T=7K
J W Meese, Phys.Rev.B9,4373(1974)
Diamond: the case of R2 centers Electron irradiation: V-, V° and Ci Ci+CC→(C-C)C° dumbell (R2) IR independent of T (4K..90K)
Anneals with Eact=1.6eV
Model:Ci* has reduced barrer for diffusion
M.E.Newton et al, Diamond and Rel.Materials 11,618 (2002)
GaN bulk crystals (n-type) Low T electron irradiation generates Ga vacancies (L1) Ga interstitials (L5,L6) ; TAnn>60K photoexcitation hν=364nm, P=100mW/cm2 at T=1.7K
Model:Bourgoin mecanism
P.Johanneson et al, Phys.Rev.B69,045208,(2004)
Intrinsic defects introduced by e- 1MeV in n-type GaAs DLTS spectra
E1 E2 E3 E7
E6 E9
Model : E1..E5 Frenkel pairs VAs-Asi E1,E2 distant pairs E3,E4,E5 closer pairs
Temperature (K)
D.Pons et al, J.Phys.C.Solid State Phys.18,3839 (1985)
Annealing of VAs-Asi pairs
E1…E5 defects anneal thermally at 500K with EA=1.55eV
Current injection allows their annealing at much lower temperatures for E3,E5 centers
GaAs: the Frenkel pair annealing via the interstitial mobility Defect concentration vs t at T=330K DLTS spectra vs tanneal T=330K, I=0.5Acm-2
E3 E5 E5 275
Temperature (K)
375 Annealing time (min)
1015/cm3
D.Stievenard et al, Phys.Rev.B33,8410(1986)
1st order kinetics: c(t,T)=c0exp(-νt)+c1 ν annealing rate
Annealing rates of E3 and E5 vs J and T
Exponential temperature dependence: E3
ν ( J , T ) = ν 0 ( J ) ⋅ exp E5
−
∆E ( J ) kT
∆E
E3, E5 center: Activation energy vs J at 300,330,355K
J Activation energy ∆E changes linearly with J: 0.388eV 0.250eV 0.188eV
Energy release model Eth=1.55eV ET(E3)=0.30eV ET-EVB=1.25eV ∆E=0.30eV
Mechanism is not energy release but Bourgoin mecanism!
Models: D.V.Lang,L.C. Kimmerling, J.Appl.Phys.47,3587(1976)
Energy release mecanism by phonon emission K =ν
H m − ∆E k ⋅T ⋅ exp
CB ∆E=ET-EV
−
VB
J.C.Bourgoin,J.W.Corbett,Radiation effects 36,157(1978)
Bougoin mechanism
M.Lannoo,J.C.Bourgoin Point Defects in Semiconductors Springer Series,Solid StateSciences 22
Successive e- and h+ Capture
Model: Bourgoin mecanism (two alternating charge states) Defect concentration Annealing rate ν(J,T)
N (t ) = N 0 ⋅ e −ν ⋅t ν ( J , T ) = ν 0 ( J ) ⋅ exp
−
∆E ( J ) kT
Deduction of the annealing rate ν from the rate of change of charge state Γ 2 charge states: empty (s) and full (b)
Rate of change of charge state:
For J=1A/cm 2 we have Γ=1010s-1
D.Stievenard et al, Phys.Rev.B33,8410(1986)
k capture rates g emission rates
Quantitative simulation of the annealing results (J,T) D.Stievenard et al, Phys.Rev.B33,8410(1986)
Recombination enhanced athermal diffusion of vacancies and interstitials
C diamond Si Ge GaAs GaN
Effects can be purposely used for device regenration
Regeneration of degraded InGaP solar cells by minority carrier injection
electron irradiation (1MeV): H2 trap in p-InGaP
Anneals by energy release mecanism
25°C
∆Ethermal=1.68eV ∆Einj=0.51eV ET=1.17eV
A.Khan et al, IEEE 1105(2002)
Conclusion:
Recombination (ionization) enhanced diffusion is a common process in all group IV and III-V semiconducors
It concerns mainly Vacancy and interstitial defects with particular carrier capture properties E3,E5 but not E1,E2 in GaAs But also impurities (Al) Models are phenomelogical (rate equations) Interesting technological applications (degradation/regeneration)
Outline I Introduction Si: the case of the monovacancy and interstitial Ge: recombination enhanced annealing of Frenkel pairs C: the interstitial case (R2) GaN: carrier induced annealing II Electron irradiated n-type GaAs the interstitial mobility /the Frenkel pair annealing III Models for recombination enhanced diffusion: Energy release model (Lang, Kimmerling) Bourgoin mecanism (Bourgoin, Corbett) IV Application of RED: Regeneration of degraded solar cells IV Conclusions
Irradiation enhanced diffusion Different types of irradiations Electron: close to threshold- correlated Frenkel pairs Proton: transmitted energy – isolated vacancy interstitial pairs Ions: cascade defects
Atomic collisions displacement of atoms Electronic excitation: free carrier generation Recombination via defects –enhanced diffusion
Enhanced diffusion mecansims
Field enhanced: charge state related Defect enhanced: interstitial formation and diffusion – kick off of substitutional impurites Al, B in Si Recombination enhanced : energy release mechanism Bourgoin mecanism saddle point changes
and Defect modification: degrade or regenerate degraded devices J.C.Bourgoin,J.W.Corbett, Radiation effects 36,157(1978)
Field enhanced
Coulomb interactions Between charged defects
Defect enhanced
Defect complexes PSi, VSi-PSi (E center)
Ionization enhanced
D(charge state) Sii (0/+/2+)in Si
Sii + AlSi → SiSi+Ali Lattice atoms Drift under applied fields (DLTS/ Ge)
SiC: Ci (C-C)C Unstable at 200°C
RED athermal diffusion Energy release mec. Bourgoin mecansim
Recombination enhanced diffusion
Intrinsic defects: Vacancies Interstitials Frenkel pairs
And Impurities: Ali in Si
Some examples:
Si the case of the vacancy and interstitial Ge Frenkel pair (in)stability under recombination C: the carbon interstitial -R2 defect GaN :the Ga nterstitials (L5,L6)
GaAs: Frenkel pair distribution modifications
Si: the thermal stability and carrier induced mobility of the Monovacancy e- irradiation of Si at low T: VSi-Sii VSi (EPR), Sii invisible, Sii related defects (EPR,LVM)
REM 4K
REM 4.2K
monovacancy
Thermal stability n-type 70K p-type 150K si 200K
G.D.Watkins, Materials Science in Semiconductor Processing 3,227 (2000)
Recombination Enhanced Diffusion in p-type Si (EPR, DLTS)
Observation of the Mono-Vacancy athermal diffusion at 4K…20K under 1.165eV photoexcitation
1 jump /40photons
low energy 350keV e- irradiation 1 jump / 103 recombinations Observation of the Ev+0.17eV level (Ali) under 1.165eV at 320K
A.P.Chatterjee et al,(1983) PhD thesis J.R.Troxel et al
Thermal stability 500K
Why is the Si interstitial so mobile in p-type Si
Low barrier for diffusion in Si+ Bourgoin mecanism between 0/2+ charge states
Annealing of e- induced defects in n-type Ge Electron irradiation: T=10K, E=1MeV creates acceptor defects Ec-60meV Defects analyzed by electrical measurements (DLTS, resistivity)
Thermal annealing : 1 stage at 69K Model: V-I recombination
Under 1.6µm light excitation: 1 stage at 27K
V.Emtsev, Materials Science in Semiconductor Processing 9,580(2006)
Low energy irradiation induced annealing in n-type Ge 1. e- 1 MeV defect generation 2. e- 500keV defect annealing at T=7K
J W Meese, Phys.Rev.B9,4373(1974)
Diamond: the case of R2 centers Electron irradiation: V-, V° and Ci Ci+CC→(C-C)C° dumbell (R2) IR independent of T (4K..90K)
Anneals with Eact=1.6eV
Model:Ci* has reduced barrer for diffusion
M.E.Newton et al, Diamond and Rel.Materials 11,618 (2002)
GaN bulk crystals (n-type) Low T electron irradiation generates Ga vacancies (L1) Ga interstitials (L5,L6) ; TAnn>60K photoexcitation hν=364nm, P=100mW/cm2 at T=1.7K
Model:Bourgoin mecanism
P.Johanneson et al, Phys.Rev.B69,045208,(2004)
Intrinsic defects introduced by e- 1MeV in n-type GaAs DLTS spectra
E1 E2 E3 E7
E6 E9
Model : E1..E5 Frenkel pairs VAs-Asi E1,E2 distant pairs E3,E4,E5 closer pairs
Temperature (K)
D.Pons et al, J.Phys.C.Solid State Phys.18,3839 (1985)
Annealing of VAs-Asi pairs
E1…E5 defects anneal thermally at 500K with EA=1.55eV
Current injection allows their annealing at much lower temperatures for E3,E5 centers
GaAs: the Frenkel pair annealing via the interstitial mobility Defect concentration vs t at T=330K DLTS spectra vs tanneal T=330K, I=0.5Acm-2
E3 E5 E5 275
Temperature (K)
375 Annealing time (min)
1015/cm3
D.Stievenard et al, Phys.Rev.B33,8410(1986)
1st order kinetics: c(t,T)=c0exp(-νt)+c1 ν annealing rate
Annealing rates of E3 and E5 vs J and T
Exponential temperature dependence: E3
ν ( J , T ) = ν 0 ( J ) ⋅ exp E5
−
∆E ( J ) kT
∆E
E3, E5 center: Activation energy vs J at 300,330,355K
J Activation energy ∆E changes linearly with J: 0.388eV 0.250eV 0.188eV
Energy release model Eth=1.55eV ET(E3)=0.30eV ET-EVB=1.25eV ∆E=0.30eV
Mechanism is not energy release but Bourgoin mecanism!
Models: D.V.Lang,L.C. Kimmerling, J.Appl.Phys.47,3587(1976)
Energy release mecanism by phonon emission K =ν
H m − ∆E k ⋅T ⋅ exp
CB ∆E=ET-EV
−
VB
J.C.Bourgoin,J.W.Corbett,Radiation effects 36,157(1978)
Bougoin mechanism
M.Lannoo,J.C.Bourgoin Point Defects in Semiconductors Springer Series,Solid StateSciences 22
Successive e- and h+ Capture
Model: Bourgoin mecanism (two alternating charge states) Defect concentration Annealing rate ν(J,T)
N (t ) = N 0 ⋅ e −ν ⋅t ν ( J , T ) = ν 0 ( J ) ⋅ exp
−
∆E ( J ) kT
Deduction of the annealing rate ν from the rate of change of charge state Γ 2 charge states: empty (s) and full (b)
Rate of change of charge state:
For J=1A/cm 2 we have Γ=1010s-1
D.Stievenard et al, Phys.Rev.B33,8410(1986)
k capture rates g emission rates
Quantitative simulation of the annealing results (J,T) D.Stievenard et al, Phys.Rev.B33,8410(1986)
Recombination enhanced athermal diffusion of vacancies and interstitials
C diamond Si Ge GaAs GaN
Effects can be purposely used for device regenration
Regeneration of degraded InGaP solar cells by minority carrier injection
electron irradiation (1MeV): H2 trap in p-InGaP
Anneals by energy release mecanism
25°C
∆Ethermal=1.68eV ∆Einj=0.51eV ET=1.17eV
A.Khan et al, IEEE 1105(2002)
Conclusion:
Recombination (ionization) enhanced diffusion is a common process in all group IV and III-V semiconducors
It concerns mainly Vacancy and interstitial defects with particular carrier capture properties E3,E5 but not E1,E2 in GaAs But also impurities (Al) Models are phenomelogical (rate equations) Interesting technological applications (degradation/regeneration)
