<s>
An	O
epitaxial	B-Algorithm
wafer	I-Algorithm
(	O
also	O
called	O
epi	B-Algorithm
wafer	I-Algorithm
,	O
epi-wafer	B-Algorithm
,	O
or	O
epiwafer	B-Algorithm
)	O
is	O
a	O
wafer	B-Architecture
of	O
semiconducting	O
material	O
made	O
by	O
epitaxial	O
growth	O
(	O
epitaxy	O
)	O
for	O
use	O
in	O
photonics	O
,	O
microelectronics	O
,	O
spintronics	O
,	O
or	O
photovoltaics	O
.	O
</s>
<s>
The	O
epi	O
layer	O
may	O
be	O
the	O
same	O
material	O
as	O
the	O
substrate	B-Architecture
,	O
typically	O
monocrystaline	O
silicon	B-Architecture
,	O
or	O
it	O
may	O
be	O
a	O
more	O
exotic	O
material	O
with	O
specific	O
desirable	O
qualities	O
.	O
</s>
<s>
Silicon	B-Architecture
epi	B-Algorithm
wafers	I-Algorithm
were	O
first	O
developed	O
around	O
1966	O
,	O
and	O
achieved	O
commercial	O
acceptance	O
by	O
the	O
early	O
1980s	O
.	O
</s>
<s>
Methods	O
for	O
growing	O
the	O
epitaxial	O
layer	O
on	O
monocrystalline	O
silicon	B-Architecture
or	O
other	O
wafers	B-Architecture
include	O
:	O
various	O
types	O
of	O
chemical	B-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
CVD	O
)	O
classified	O
as	O
Atmospheric	B-Algorithm
pressure	I-Algorithm
CVD	I-Algorithm
(	O
APCVD	B-Algorithm
)	O
or	O
metal	B-Algorithm
organic	I-Algorithm
chemical	I-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
MOCVD	B-Algorithm
)	O
,	O
as	O
well	O
as	O
molecular	B-Algorithm
beam	I-Algorithm
epitaxy	I-Algorithm
(	O
MBE	O
)	O
.	O
</s>
<s>
Two	O
"	O
kerfless	O
"	O
methods	O
(	O
without	O
abrasive	O
sawing	O
)	O
for	O
separating	O
the	O
epitaxial	O
layer	O
from	O
the	O
substrate	B-Architecture
are	O
called	O
"	O
implant-cleave	O
"	O
and	O
"	O
stress	O
liftoff	O
"	O
.	O
</s>
<s>
A	O
method	O
applicable	O
when	O
the	O
epi-layer	O
and	O
substrate	B-Architecture
are	O
the	O
same	O
material	O
employs	O
ion	O
implantation	O
to	O
deposit	O
a	O
thin	O
layer	O
of	O
crystal	O
impurity	O
atoms	O
and	O
resulting	O
mechanical	O
stress	O
at	O
the	O
precise	O
depth	O
of	O
the	O
intended	O
epi	O
layer	O
thickness	O
.	O
</s>
<s>
In	O
the	O
dry	O
stress	O
lift-off	O
process	O
applicable	O
when	O
the	O
epi-layer	O
and	O
substrate	B-Architecture
are	O
suitably	O
different	O
materials	O
,	O
a	O
controlled	O
crack	O
is	O
driven	O
by	O
a	O
temperature	O
change	O
at	O
the	O
epi/wafer	O
interface	O
purely	O
by	O
the	O
thermal	O
stresses	O
due	O
to	O
the	O
mismatch	O
in	O
thermal	O
expansion	O
between	O
the	O
epi	O
layer	O
and	O
substrate	B-Architecture
,	O
without	O
the	O
necessity	O
for	O
any	O
external	O
mechanical	O
force	O
or	O
tool	O
to	O
aid	O
crack	O
propagation	O
.	O
</s>
<s>
It	O
was	O
reported	O
that	O
this	O
process	O
yields	O
single	O
atomic	O
plane	O
cleavage	O
,	O
reducing	O
the	O
need	O
for	O
post	O
lift-off	O
polishing	O
,	O
and	O
allowing	O
multiple	O
reuses	O
of	O
the	O
substrate	B-Architecture
up	O
to	O
10	O
times	O
.	O
</s>
<s>
Solar	O
cells	O
,	O
or	O
photovoltaic	O
cells	O
(	O
PV	O
)	O
for	O
producing	O
electric	O
power	O
from	O
sunlight	O
can	O
be	O
grown	O
as	O
thick	O
epi	B-Algorithm
wafers	I-Algorithm
on	O
a	O
monocrystalline	O
silicon	B-Architecture
"	O
seed	O
"	O
wafer	B-Architecture
by	O
chemical	B-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
CVD	O
)	O
,	O
and	O
then	O
detached	O
as	O
self-supporting	O
wafers	B-Architecture
of	O
some	O
standard	O
thickness	O
(	O
e.g.	O
,	O
250μm	O
)	O
that	O
can	O
be	O
manipulated	O
by	O
hand	O
,	O
and	O
directly	O
substituted	O
for	O
wafer	B-Architecture
cells	O
cut	O
from	O
monocrystalline	O
silicon	B-Architecture
ingots	O
.	O
</s>
<s>
Solar	O
cells	O
made	O
with	O
this	O
technique	O
can	O
have	O
efficiencies	O
approaching	O
those	O
of	O
wafer-cut	O
cells	O
,	O
but	O
at	O
appreciably	O
lower	O
cost	O
if	O
the	O
CVD	O
can	O
be	O
done	O
at	O
atmospheric	O
pressure	O
in	O
a	O
high-throughput	O
inline	O
process	O
.	O
</s>
<s>
The	O
surface	O
of	O
epitaxial	B-Algorithm
wafers	I-Algorithm
may	O
be	O
textured	O
to	O
enhance	O
light	O
absorption	O
.	O
</s>
<s>
In	O
April	O
2016	O
,	O
the	O
company	O
of	O
Santa	O
Clara	O
,	O
California	O
,	O
in	O
collaboration	O
with	O
the	O
European	O
research	O
institute	O
IMEC	O
announced	O
that	O
they	O
achieved	O
a	O
22.5	O
%	O
cell	O
efficiency	O
of	O
an	O
epitaxial	O
silicon	B-Architecture
cell	O
with	O
an	O
nPERT	O
(	O
n-type	O
passivated	O
emitter	O
,	O
rear	O
totally-diffused	O
)	O
structure	O
grown	O
on	O
6-inch	O
(	O
150mm	O
)	O
wafers	B-Architecture
.	O
</s>
<s>
In	O
September	O
2015	O
Hanwha	O
Q	O
Cells	O
presented	O
an	O
achieved	O
conversion	O
efficiency	O
of	O
21.4	O
%	O
(	O
independently	O
confirmed	O
)	O
for	O
screen-printed	O
solar	O
cells	O
made	O
with	O
Crystal	O
Solar	O
epitaxial	B-Algorithm
wafers	I-Algorithm
.	O
</s>
<s>
In	O
June	O
2015	O
,	O
it	O
was	O
reported	O
that	O
heterojunction	O
solar	O
cells	O
grown	O
epitaxially	O
on	O
n-type	O
monocrystalline	B-Architecture
silicon	I-Architecture
wafers	I-Architecture
had	O
reached	O
an	O
efficiency	O
of	O
22.5	O
%	O
over	O
a	O
total	O
cell	O
area	O
of	O
243.4cm	O
.	O
</s>
<s>
In	O
2016	O
,	O
a	O
new	O
approach	O
was	O
described	O
for	O
producing	O
hybrid	O
photovoltaic	O
wafers	B-Architecture
combining	O
the	O
high	O
efficiency	O
of	O
III-V	O
multi-junction	O
solar	O
cells	O
with	O
the	O
economies	O
and	O
wealth	O
of	O
experience	O
associated	O
with	O
silicon	B-Architecture
.	O
</s>
