Valence Band Anticrossing in III-Bi-V Alloys

36 Pages·2010·2.06 MB·German

by  Kirstin Alberi

Wladek Walukiewicz
Lawrence Berkeley National Laboratory, Berkeley CA
In collaboration with EMAT-Solar group
http://emat-solar.lbl.gov/
Valence Band Anticrossing in III-Bi-V Alloys
J. Ager, K. M. Yu, Liliental-Weber, J. Denlinger, O. Dubon,
E. E. Haller, J. Wu
LBNL and UC Berkeley
K. Alberi, X. Li, D. Speaks, M. Mayer, R. Broesler, A.
Levander
Students, UC Berkeley
Collaborations
• J. Geisz, NREL (InGaAs(N))
• C. Tu, UCSD (GaP(N), InP(N))
• C. Skierbiszewski, Unipres (InGaAs(N))
• A. Ramdas, Purdue University (ZnTe(Se), ZnTe(S)..)
• I. K. Sou, UST, Hong Kong (ZnSe(Te), ZnS(Te))
• I. Suemune, (Hokkaido University) (InGaAs(N))
• T. Kuech, University of Wisconsin (GaN(As))
• Y. Nabetani, University of Yamanashi (ZnSe(O), ZnTe(O))
• J. A Gupta, NRC, Canada (GaAs(Sb))
• S. Watkins, Simon Frasier (GaAs(Sb))
• A. Krotkus, SRI, Vilnius (GaAs(Bi)
• J. Blacksberg, JPL (Ge(Sn))
• T. Foxon, S. Novikov, University of Nottingham (GaN(As))
• J. Furdyna, University of Notre Dame (GaAs(Mn))
Outline

Highly Mismatched Semiconductor Alloys

Conduction and Valence Band Anticrossing

Key examples of highly mismatched alloys (HMAs)

GaN As
x 1-x

ZnO Se
x 1-x

Group III-Bi-V highly mismatched alloys

Electronic Band Structure Engineering of HMAs

Potential applications of HMAs (including bismides)

Conclusions and outlook
Normal alloying: well matched alloys
2.8
3.6
2.6 GaAs P
1-y y ZnSe S
3.4 1-y y
2.4 )
V
e
(

) y
V 2.2 g 3.2
e r
( e
y n
g E E
re 2 X p
n a 3
E G

d
1.8 n E
a
E B 
 2.8
1.6
1.4
2.6
0 0.2 0.4 0.6 0.8 1
0 0.2 0.4 0.6 0.8 1
GaAs GaP
Composition, y ZnSe Composition, y ZnS
Relatively easy to grow in the whole composition range
Small deviations from linear interpolation between end point compounds
Anion Site Alloys
Electronegativities, X and atomic radii, R
IV V VI
• A large variety of
C N O
potential alloys.
2.6 X=3.0 X=3.4
R=0.075 nm R=0.073 nm • Well matched alloys:
Si P S replacing atoms with
1.9 X=2.2 X=2.6
similar properties
R=0.12 nm R=0.11 nm
• What happens when As
Ge As Se
is replaced with very
X=2.2 X=2.6
1.9
much different N or Se
R=0.13 nm R=0.12 nm
with O?
Sn Sb Te
2.0 2.1 2.1
R=0.14 nm R=0.14 nm
III-Vs and II-VIs HMAs
2.70
ZnO Se
2.68 x 1-x
VCA 295 K
VCA )
V 2.66
e
(
2.64
y
g
r 2.62
e
n
E 2.60

p
a 2.58
g
-
d 2.56
n
a Exp.Data
2.54
B
BAC
2.52
2.50
0.000 0.005 0.010 0.015 0.020
Oxygen Concentration (x)
Drastic deviation from linear interpolation between end point
compounds
W. Shan, et. al., J. Phys.: Condens Matter, 16 S3355 (2004)
W. Shan, et. al., Appl. Phys. Lett., 83, 299 (2003)
Band Anticrossing in HMA:
Dilute nitride alloys: GaAs N
1-x x
• Interaction of
localized N levels
with extended
states of the
conduction band.
• Homogenous
broadening within
coherent potential
approximation
1    
   C  L C  L 2 2 
E k  E k  E  E k  E  4C x
 
 NM
2  
W. Shan etl al., Phys. Rev. Lett. 82, 1221-1224 (1999);
J. Wu et al. Semicon. Sci. Technol. 17, 862 (2002).
Highly mismatched Alloys
Electronegativities, X and atomic radii, R
IV V VI
• A large variety of potential
C N O
highly mismatched alloys.
2.6 X=3.0 X=3.4
III-N -V
R=0.075 nm R=0.073 nm x 1-x
II-O -VI
Si P S x 1-x
• Compared to normal alloys,
1.9 X=2.2 X=2.6
they are difficult to synthesize
R=0.12 nm R=0.11 nm
• Require non-equilibrium
Ge As Se
synthesis
X=2.2 X=2.6
1.9
R=0.13 nm R=0.12 nm
Sn Sb Te
2.0 2.1 2.1
R=0.14 nm R=0.14 nm
Synthesis of HMAs by ion implantation and pulsed
laser melting (II-PLM)
N ions Time Resolved Reflectivity
ion induced damage
GaAs
Pulsed laser melting (PLM)
Homogenized excimer laser pulse
(=248 nm, 30 ns FWHM, ~0.2-0.8 J/cm2)
ion indGuLcaiqeNudAi ddsamage
GaAs
RTA
 Lliquid phase epitaxy at submicrosecond time scales
GaNAs
 Supersaturation of implanted species
GaAs
 Suppression of secondary phases
Alloys with local level below the direct CBE
III-V II-VI
E
oxy
E
N
E
FS
G G I Z Z M C
n
a a P n n n d
P A S T T T
s e e e e
Oxygen level in ZnTe and MnTe is ~0.2 eV
below the conduction band (CB) edge
Can it be used to form a sparate band?