1. Donor-Acceptor Complexes in ZnO
M. Türker, M. Deicher, H. Wolf, and Th. Wichert
Universität des Saarlandes
Technische Physik, Saarbrücken
The ISOLDE Collaboration
CERN, Geneva, Switzerland

2. Zinc Oxide EG = 3.37 eV at RT Eexciton binding = 60 meV Bulk crystal
Easy to dope n-type
Difficult to dope p-type Zn NO O
Bulk crystal
c-axis
N-typ ZnO Anwendung Transparent Conducting Oxide
Exziton Bindungsenergy von ZnO is größer als von GaN und hat daher eine höhere Wahrscheinlichkeit zu lasen (laser)
ZnO ist günstiger in der Herstellung als GaN
EG=3,37eV bei RT
gut n-typ, schwer p-typ 2

3. How to enhance p-type doping?
possible
In-N2 complex
Donor-Acceptor Codoping
Yamamoto and Katayama-Yoshida
Physica B 302 (2001) 155
Donor-Acceptor Cluster-Doping
Wang and Zunger
Physical Review Letters 90 (2003) Zn O NO
InZn
Inwiefern ist das Bilden solcher Komplexe verantwortlich für die bessere p-Dotierung?
Reaktives Sputtern
N-doped Resistivity 9x103 OHMcm
In-N codoped Resistivity 23.7 OHMcm 3

4. How to enhance p-type doping?
possible
In-N2 complex
Donor-Acceptor Codoping
Yamamoto and Katayama-Yoshida
Physica B 302 (2001) 155
Donor-Acceptor Cluster-Doping
Wang and Zunger
Physical Review Letters 90 (2003) Zn O NO
Electrical properties of ZnO films
Sample
Carrier
type
concentration
InZn
N doped p
3.25  1014 cm-3
In-Nx codoped
3.51  1017 cm-3
increase by
factor 1000
Chen, Lu, Ye, Lin, Zhao, Ye, Li, and Zhu
Applied Physics Letters 87 (2005)
Inwiefern ist das Bilden solcher Komplexe verantwortlich für die bessere p-Dotierung?
Reaktives Sputtern
N-doped Resistivity 9x103 OHMcm
In-N codoped Resistivity 23.7 OHMcm 3

5. Codoping with In and N by implantation
possible
In-N2 complex
SIMS depth profiling as
implanted
TA=1073K
t=60min
1020
1019
1018
1017
1016 Zn
Concentration [ions/cm3] O NO N In
I n
InZn In
I n N
depth [μm]
Park, Sakaguchi, Ohashi, Hishita, and Haneda
Applied Surface Science (2003) 359
Eine Methode, die sensitiv auf die mikroskopisch lokale Umgebung auf atomarer Ebene ist
rb112 4 5

6. Perturbed Angular Correlation (PAC)
Electrical
field gradient Vij
strength Vzz
symmetry η =
orientation
EFG ~ r – 3
- microscopic local Zn Zn
Vxx - Vyy
Vzz O O NO
111InZn
111InZn
EFGlattice
EFGdefect
Sensitive to microscopic environment
d.h. sensitiv auf Störungen in unmittelbarer Nachbarschaft der Sonde, also sensitiv auf In-Defekt Komplexe
Proportional to r-3 5 6

7. Perturbed Angular Correlation (PAC)
Donor-acceptor
interaction
111In
T1/2 = 3 d EC 1
Observation
T1/2 = 85 ns Q 2
111Cd
Rb112_2
ct002 6 7

8. Perturbed Angular Correlation (PAC)
Donor-acceptor
interaction
111In
EFG ≠ 0 ω1 ω3 ω2
T1/2 = 3 d EC 1
Observation
T1/2 = 85 ns Q 2
111Cd
Q = w1=
e Q Vzz h 10
3 p
Q: quadrupole coupling constant 6 8

9. Intrinsic EFGlattice of ZnO
111In implantation; TA = 1100K tA = 30min
c-axis :
R(t) Fourier transforms
EFGlattice
Q = 31MHz
 = 0
f = 86%
detector
t [ns] w [Mrad/s]
45°-geometry
detector
rb112 7 9

10. Codoping of ZnO Indium penetration in ZnO depth 974 Å depth 3368 Å
111In implantation; TA = 1100K tA = 30min
R(t) Fourier transforms
depth 974 Å
EFGlattice
Q = 31MHz
 = 0
f = 86%
E = 400 keV
(atoms/cm3) / (atoms/cm2) In
t [ns] w [Mrad/s]
depth 3368 Å
Group V energy penetration depth
N keV Å
P keV Å As
Sb keV Å
E = 220 keV
(atoms/cm3) / (atoms/cm2) N
rb112 8 10

11. Indium-Nitrogen codoping of ZnO
N (220keV) + 111In (400keV); TA = 1000K tA = 20min
Q2
Q1
R(t)
FT(ω)
Q2
Q1
R(t)
FT(ω)
t [ns] w [Mrad/s]
Rb137_06
Rb137_05 9 11

12. Indium-Nitrogen codoping of ZnO
N (220keV) + 111In (400keV); TA = 1000K tA = 20min
Q2
2 axial symmetrical
EFGdefect:
Q1
R(t)
FT(ω)
c-axis oriented
Q1=209(1)MHz
=0
f=2%
Q2
Q1
basal plane oriented
Q2=234(1)MHz
≤0
f=5%
R(t)
FT(ω)
t [ns] w [Mrad/s]
w [Mrad/s]
Rb137_06
Rb137_05 9 12

13. Indium-Nitrogen codoping of ZnO
Isochronic annealing f0 f2 f1
Rb166: T_M-Reihe
Ct009: T_A-Reihe 10 13

14. Indium-Phosphorus codoping of ZnO
P (400keV) + 111In (400keV); TA = 800K tA = 60min
Q2
2 axial symmetrical
EFGdefect:
Q1
R(t)
FT(ω)
c-axis oriented
Q1=153(1)MHz
=0
f=2%
Q1
Q2
basal plane oriented
Q2=176(1)MHz
≤0
f=10%
R(t)
FT(ω)
t [ns] w [Mrad/s]
Rb161_02
Rb161_03 11 14

15. Formation of Indium-Acceptor-Pairs in II-VI semiconductors
wurtzite
cubic
theoretical
ZnO
*ZnSe
*ZnTe
*CdTe
111In – N
209
234
271
262
280
111In – P
153
176
219
222
212
111In – As
196
199
186
111In – Sb
169
156
167
**CdTe
274
224
190
162
* Ostheimer, Jost, Filz, Lauer, Wolf, and Wichert
Applied Physics Letters 69 (1996) 2840
* * Lany, Ostheimer, Wolf, and Wichert
Hyperfine Interactions 136/137 (2001) 619 12 15

16. Formation of Indium-Acceptor-Pairs in Zinc Oxide
Q [MHz]
f [%] η
Orientation
111In – N
209 (1)
239 (1) 2 5
≤0.1
c-axis
basal plane
111In – P
155 (1)
175 (1) 10
111In – Sb
169 (1) / 9 13 16

17. Possible configurations of In-NX Complexes
≠0
=0
≤0.1
In-N3
≠0
=0
=0
In-N4 14

18. Summary Donor–acceptor codoping of ZnO by ion implantation
Aim: analysis of the microscopic environment on atomic level
Tool: Perturbed Angular Correlation to obtain structural information
PAC
In-N1: 2 EFG
In-P1: 2 EFG 15

19. Work in progress Li Na 77Br K Group VII Group I Donor Acceptor
77Br/ 77Se (60keV); TA = 1100K
77Br
Group VII
Donor
ISOLDE
CERN
Group I
Acceptor Li Na K
Q=403 MHz
Implantations: Michael Uhrmacher and Daniel Jürgens (U Göttingen)
Financial support by BMBF 05KK7TS1 16

21. InN1-Komplex PAC-Messungen: - 2 axialsymmetrische EFGDefekt
=0
≤0
In-N-Komplex
In-P-Komplex
- 1 axialsymmetrisches EFGDefekt
In-Sb-Komplex

22. Intrinsic EFGlattice of ZnO
111In diffusion; T = 1400K; t = 4d
R(t) Fourier transforms
output
frequency Q
fraction f
symmetry
orientation
c-axis :
EFGlattice
Q = 31MHz
= 0
f = 95%
detector
45°-geometry
detector
ct002 22 7 22

23. Indium-Nitrogen codoping of ZnO
TAnneal-sequence
TMeasure-sequence
T = 1000K
t = 30min
Q2
Q2
Q1
Q1
Q0
Q0 f0 f0 f2 f2 f1 f1
Rb166: T_M-Reihe
Ct009: T_A-Reihe 10 23

24. Perturbed Angular Correlation (PAC)
111In
PAC time spectra R(t) using the example
of polycrystalline ZnO sample
T1/2 = 3 d EC
R(t) Fourier transforms
EFG ≠ 0 ω1 ω3 ω2 1
T1/2 = 85 ns Q 2
111Cd
Q = w1=
e Q Vzz h 10
3 p
Q: quadrupole coupling constant
η=0; w1:w2:w3=3:2:1
η: asymmetry parameter
Ct021_04 6 24

25. Indium-Antimon codoping of ZnO
Sb (400keV) + 111In (400keV); TA = 900K tA = 30min
Q2
1 axial symmetrical
EFGdefect:
R(t)
FT(ω)
Q2
basal plane oriented
Q2=169(1)MHz
≈0
f=9%
R(t)
FT(ω)
t [ns] w [Mrad/s] 12 25

26. Perturbed Angular Correlation (PAC)
111In diffusion; T = 1400K; t = 4d
R(t) Fourier transforms
EFGlattice
Q = 31MHz
= 0
f = 95%
Ct002
rb125 6 26

27. polykristallin einkristallin Detektor c-Achse Probe
c-Achse ^ Detektor Ebene
45°-Geometrie
polykristallin
einkristallin 27

28. Implantation 111In (400 keV) 14N (55 keV) 14N (220 keV) 14N (110 keV)
TA=1073K
t=30min
t=60min as
implanted
TA=1073K
t=30min
t=60min as
implanted
111In (400 keV)
Park, Sakaguchi, Ohashi, Hishita und Haneda
Applied Surface Science (2003)
14N (55 keV)
14N (220 keV)
14N (110 keV) 28