thermally stimulated currents method ioana pintilie a) national institute of materials physics,...
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![Page 1: Thermally Stimulated Currents Method Ioana Pintilie a) National Institute of Materials Physics, Bucharest-Magurele, P.O.Box MG-7, Romania b) Institute](https://reader035.vdocument.in/reader035/viewer/2022081813/56649eb55503460f94bbe488/html5/thumbnails/1.jpg)
Thermally Stimulated Currents Method
Ioana Pintiliea)National Institute of Materials Physics,
Bucharest-Magurele, P.O.Box MG-7, Romania
b)Institute for Experimental Physics,
Hamburg University, D-22761, Germany
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Electrical properties of Point Defects in the space charge region
)()(
)()(;
)()(
)()(
TeTe
TeNTn
TeTe
TeNTn
pn
nTE
donorT
pn
pTE
acceptorT
Tk
ETETTe
b
VCapnpn
,,,
)(exp*)(~)(
)()()()()( 00 TnTeqTnTeqT donorTp
acceptorTnE
Defect´ signature – emission rates
2) Leakage current density
1) Effective doping concentration
- given by the steady state occupancy
of the defect/impurity levels in SCR
Effective generation centers (acceptor like)
P+
N+
Electrons in the conduction band
Holes in the valence band
N
NA
ND (+)
(-)/0
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Thermally Stimulated Currents Method
1. cooling the sample
2. filling of the traps:
- during cooling under 0 bias (majority carriers)
- or carrier injection at low T by biasing the diode/ illumination
3. recording the TSCurrent – the current due to charge emission from the traps is recorded as function of temperature during the heating of the sample with constant rate
p+- n – n+ diodes
n+
p+
n
Electrons in the conduction band
Holes in the valence bandI
Current
d
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Tk
EENce
vc
nNp
withdt
dpxAqI
dt
dnxAqI
npcpedt
dp
pncnedt
dndt
dn
dt
dp
penpcpncnedt
dn
B
VCTVCpnpn
pnthpnpn
ttt
vhTSC
ceTSC
tptpv
tntnc
tt
ptptntnt
,,,,
,,,,
exp
;
2
2
``)(`)(1
exp(*)(*)(*2
*)(*)(
0
0 dTTeTeTeTnqTxA
TIT
T
pnnfillte
TSC
nt(Tfill), pt(Tfill):
• electrons injection nt(Tfill) = Nt
• holes injectionpt(Tfill) = Nt
• forward injection/illumination under 0Vpt(Tfill) = Ntcp/(cn+cp)
nt(Tfill) = Ntcn/(cn+cp)
j
jt
i
itDeff
eff
bi
TpTnNTN
dTN
TVV
qTx
)()()(
)(
)(2)(
![Page 5: Thermally Stimulated Currents Method Ioana Pintilie a) National Institute of Materials Physics, Bucharest-Magurele, P.O.Box MG-7, Romania b) Institute](https://reader035.vdocument.in/reader035/viewer/2022081813/56649eb55503460f94bbe488/html5/thumbnails/5.jpg)
20 40 60 80 100 120 140 160 180 200-5
0
5
10
15
20
25
30
35
40electron traps
15e12
7e9e
8e
5
3e1e
TSC
(pA)
Temperature (K)5 10 15 20 25 30
0.1
1
10
100 12 20 min. at 300 C
3e
5
9e
15e 8e
7e
Ha3
=0.095 eVH
a5=0.166 eV
Ha7
=0.22 eVH
a8=0.3 eV
Ha9
=0.32 eVH
a12=0.37 eV
Ha15
=0.45 eV
Log(
TSC
)
1000/T(K)
• Activation enthalpy - the thermal cleanning procedureFor defects with en(T) >> ep(T) (or viceversa) and for constant SCR width (x(T)=d) the increasing part of the TSC peak is ~ exp (Hn (p)/kT)
Hn (p) can be determined from Arrhenius plots
``)(`)(1
exp(*)(*)(*2
*)(*)(
0
0 dTTeTeTeTnqTxA
TIT
T
pnnfillte
TSC
• Concentration of defects – by integrating the TSC peak
• Capture cross sections – by fitting the TSC peaks
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``)(`)(1
exp(*)(*)(*2
*)(*)(
0
0 dTTeTeTeTnqTxA
TIT
T
pnnfillte
TSC
j
jt
i
itDeff
eff
bi
TpTnNTN
dTN
TVV
qTx
)()()(
,)(
)(2)(
x = d
x < dx < d
x < dx < dx =d
Nt >20xNd
Problems - Temperature variation of SCR width (x(T) < d)
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60 80 100 120 140 160 180 200 220
100
200
300
400
500
600 RB = 100 V E&H(147K) protons neutrons
TS
C (
pA)
Temperature (K)
80 100 120 140 160 180 2000
100
200
300
400
500proton irradiated RB= 100 V
SCR
wid
th (
m)
Temperature (K)
130 140 150 160 170 180
0
50
100
150
200
250
300
350neutron irradiated
E&H(165)
E&H(147) RB= 200 V RB= 150 V RB= 100 V fit 200 V fit 150 V fit 100 V
TS
C (
pA)
Temperature (K)80 100 120 140 160 180 200
200
400
600
800neutron irradiated RB= 200 V RB= 150 V RB= 100 V
SCR
wid
th (
m)
Temperature (K)
``)(`)(
1exp(*)(*)(*)(~)(
0
i
T
T
ip
in
infill
it dTTeTeTeTnTxTITSC
j
jt
i
itDeff
eff
bi
TpTnNTN
dTN
TVV
qTx
)()()(
,)(
)(2)(
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Evaluation of temperature dependent capture cross sections
Diodes with initial doping of Nd = 5·1011 cm-3, Nt ~ 2·1013 cm-3
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P+
N+
Electrons in the conduction band
Holes in the valence band
N
NA
ND (+)
(-)/0
Steady state occupancy in the SCREmission from the filled traps
Deep acceptors acting like Generation centers
N+
P+
N
Electrons in the conduction band
Holes in the valence band
I
Current
nT (T) ~ 80%NT
what can be detected is
20% NT emission of electrons
80% NT emission of holes
``)(`)(1
exp(*)(*)(*2
**)(
0
0 dTTeTeTeTnqdA
TIT
T
pnnfillte
TSC
![Page 10: Thermally Stimulated Currents Method Ioana Pintilie a) National Institute of Materials Physics, Bucharest-Magurele, P.O.Box MG-7, Romania b) Institute](https://reader035.vdocument.in/reader035/viewer/2022081813/56649eb55503460f94bbe488/html5/thumbnails/10.jpg)
Thermally Stimulated Currents Method
• limitation:
- TSCmin > 0.1 pA
- TSCmax – given by the possibility of depleting the diodes thickness (RBmax=500 V) during T scan
- no direct measurement of the capture cross sections possible
• advantage:
- investigation of diodes with high traps concentration
NT >ND-NA
- determination of ionisation energy (Thermal cleaning procedure)
- suitable for the detection of donor activity (Poole-Frenkel effect)
• disadvantage:
- no direct defect identification possible
- combination with other methods (e.g. EPR, FTIR)