<s>
In	O
semiconductor	O
production	O
,	O
doping	B-Algorithm
is	O
the	O
intentional	O
introduction	O
of	O
impurities	O
into	O
an	O
intrinsic	O
semiconductor	O
for	O
the	O
purpose	O
of	O
modulating	O
its	O
electrical	O
,	O
optical	O
and	O
structural	O
properties	O
.	O
</s>
<s>
When	O
on	O
the	O
order	O
of	O
one	O
dopant	O
atom	B-Language
is	O
added	O
per	O
100	O
million	O
atoms	O
,	O
the	O
doping	B-Algorithm
is	O
said	O
to	O
be	O
low	O
or	O
light	O
.	O
</s>
<s>
When	O
many	O
more	O
dopant	O
atoms	O
are	O
added	O
,	O
on	O
the	O
order	O
of	O
one	O
per	O
ten	O
thousand	O
atoms	O
,	O
the	O
doping	B-Algorithm
is	O
referred	O
to	O
as	O
high	O
or	O
heavy	O
.	O
</s>
<s>
This	O
is	O
often	O
shown	O
as	O
n+	O
for	O
n-type	O
doping	B-Algorithm
or	O
p+	O
for	O
p-type	O
doping	B-Algorithm
.	O
</s>
<s>
(	O
See	O
the	O
article	O
on	O
semiconductors	O
for	O
a	O
more	O
detailed	O
description	O
of	O
the	O
doping	B-Algorithm
mechanism	O
.	O
)	O
</s>
<s>
In	O
the	O
context	O
of	O
phosphors	O
and	O
scintillators	O
,	O
doping	B-Algorithm
is	O
better	O
known	O
as	O
activation	O
;	O
this	O
is	O
not	O
to	O
be	O
confused	O
with	O
dopant	O
activation	O
in	O
semiconductors	O
.	O
</s>
<s>
Doping	B-Algorithm
is	O
also	O
used	O
to	O
control	O
the	O
color	O
in	O
some	O
pigments	O
.	O
</s>
<s>
The	O
effects	O
of	O
impurities	O
in	O
semiconductors	O
(	O
doping	B-Algorithm
)	O
were	O
long	O
known	O
empirically	O
in	O
such	O
devices	O
as	O
crystal	O
radio	O
detectors	O
and	O
selenium	O
rectifiers	O
.	O
</s>
<s>
A	O
doping	B-Algorithm
process	O
was	O
formally	O
developed	O
by	O
John	O
Robert	O
Woodyard	O
working	O
at	O
Sperry	O
Gyroscope	O
Company	O
during	O
World	O
War	O
II	O
.	O
</s>
<s>
Though	O
the	O
word	O
doping	B-Algorithm
is	O
not	O
used	O
in	O
it	O
,	O
his	O
US	O
Patent	O
issued	O
in	O
1950	O
describes	O
methods	O
for	O
adding	O
tiny	O
amounts	O
of	O
solid	O
elements	O
from	O
the	O
nitrogen	O
column	O
of	O
the	O
periodic	O
table	O
to	O
germanium	O
to	O
produce	O
rectifying	O
devices	O
.	O
</s>
<s>
The	O
demands	O
of	O
his	O
work	O
on	O
radar	B-Application
prevented	O
Woodyard	O
from	O
pursuing	O
further	O
research	O
on	O
semiconductor	B-Algorithm
doping	I-Algorithm
.	O
</s>
<s>
In	O
a	O
non-intrinsic	O
semiconductor	O
under	O
thermal	O
equilibrium	O
,	O
the	O
relation	O
becomes	O
(	O
for	O
low	O
doping	B-Algorithm
)	O
:	O
</s>
<s>
Silicon	O
's	O
ni	O
,	O
for	O
example	O
,	O
is	O
roughly	O
1.08	O
×1010	O
cm−3	O
at	O
300	O
kelvins	B-Operating_System
,	O
about	O
room	O
temperature	O
.	O
</s>
<s>
In	O
general	O
,	O
increased	O
doping	B-Algorithm
leads	O
to	O
increased	O
conductivity	O
due	O
to	O
the	O
higher	O
concentration	O
of	O
carriers	O
.	O
</s>
<s>
Often	O
superscript	O
plus	O
and	O
minus	O
symbols	O
are	O
used	O
to	O
denote	O
relative	O
doping	B-Algorithm
concentration	O
in	O
semiconductors	O
.	O
</s>
<s>
For	O
example	O
,	O
n+	O
denotes	O
an	O
n-type	O
semiconductor	O
with	O
a	O
high	O
,	O
often	O
degenerate	O
,	O
doping	B-Algorithm
concentration	O
.	O
</s>
<s>
Even	O
degenerate	O
levels	O
of	O
doping	B-Algorithm
imply	O
low	O
concentrations	O
of	O
impurities	O
with	O
respect	O
to	O
the	O
base	O
semiconductor	O
.	O
</s>
<s>
Doping	B-Algorithm
concentration	O
for	O
silicon	O
semiconductors	O
may	O
range	O
anywhere	O
from	O
1013	O
cm−3	O
to	O
1018	O
cm−3	O
.	O
</s>
<s>
Doping	B-Algorithm
concentration	O
above	O
about	O
1018	O
cm−3	O
is	O
considered	O
degenerate	O
at	O
room	O
temperature	O
.	O
</s>
<s>
Degenerately	O
doped	B-Algorithm
silicon	I-Algorithm
contains	O
a	O
proportion	O
of	O
impurity	O
to	O
silicon	O
on	O
the	O
order	O
of	O
parts	O
per	O
thousand	O
.	O
</s>
<s>
This	O
proportion	O
may	O
be	O
reduced	O
to	O
parts	O
per	O
billion	O
in	O
very	O
lightly	O
doped	B-Algorithm
silicon	I-Algorithm
.	O
</s>
<s>
Doping	B-Algorithm
a	O
semiconductor	O
in	O
a	O
good	O
crystal	O
introduces	O
allowed	O
energy	O
states	O
within	O
the	O
band	O
gap	O
,	O
but	O
very	O
close	O
to	O
the	O
energy	O
band	O
that	O
corresponds	O
to	O
the	O
dopant	O
type	O
.	O
</s>
<s>
Because	O
EB	O
is	O
so	O
small	O
,	O
room	O
temperature	O
is	O
hot	O
enough	O
to	O
thermally	B-Algorithm
ionize	I-Algorithm
practically	O
all	O
of	O
the	O
dopant	O
atoms	O
and	O
create	O
free	O
charge	O
carriers	O
in	O
the	O
conduction	O
or	O
valence	O
bands	O
.	O
</s>
<s>
Sometimes	O
the	O
intrinsic	O
Fermi	O
level	O
,	O
Ei	O
,	O
which	O
is	O
the	O
Fermi	O
level	O
in	O
the	O
absence	O
of	O
doping	B-Algorithm
,	O
is	O
shown	O
.	O
</s>
<s>
For	O
low	O
levels	O
of	O
doping	B-Algorithm
,	O
the	O
relevant	O
energy	O
states	O
are	O
populated	O
sparsely	O
by	O
electrons	O
(	O
conduction	O
band	O
)	O
or	O
holes	O
(	O
valence	O
band	O
)	O
.	O
</s>
<s>
an	O
expression	O
which	O
is	O
independent	O
of	O
the	O
doping	B-Algorithm
level	O
,	O
since	O
(	O
the	O
band	O
gap	O
)	O
does	O
not	O
change	O
with	O
doping	B-Algorithm
.	O
</s>
<s>
Some	O
dopants	O
are	O
added	O
as	O
the	O
(	O
usually	O
silicon	O
)	O
boule	B-Algorithm
is	O
grown	O
by	O
Czochralski	O
method	O
,	O
giving	O
each	O
wafer	B-Architecture
an	O
almost	O
uniform	O
initial	O
doping	B-Algorithm
.	O
</s>
<s>
Alternately	O
,	O
synthesis	O
of	O
semiconductor	O
devices	O
may	O
involve	O
the	O
use	O
of	O
vapor-phase	B-Algorithm
epitaxy	I-Algorithm
.	O
</s>
<s>
In	O
vapor-phase	B-Algorithm
epitaxy	I-Algorithm
,	O
a	O
gas	O
containing	O
the	O
dopant	O
precursor	O
can	O
be	O
introduced	O
into	O
the	O
reactor	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
case	O
of	O
n-type	O
gas	O
doping	B-Algorithm
of	O
gallium	O
arsenide	O
,	O
hydrogen	O
sulfide	O
is	O
added	O
,	O
and	O
sulfur	O
is	O
incorporated	O
into	O
the	O
structure	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
semiconductors	O
in	O
general	O
,	O
only	O
a	O
very	O
thin	O
layer	O
of	O
the	O
wafer	B-Architecture
needs	O
to	O
be	O
doped	O
in	O
order	O
to	O
obtain	O
the	O
desired	O
electronic	O
properties	O
.	O
</s>
<s>
To	O
define	O
circuit	O
elements	O
,	O
selected	O
areas	O
—	O
typically	O
controlled	O
by	O
photolithography	B-Algorithm
—	O
are	O
further	O
doped	O
by	O
such	O
processes	O
as	O
diffusion	O
and	O
ion	O
implantation	O
,	O
the	O
latter	O
method	O
being	O
more	O
popular	O
in	O
large	O
production	O
runs	O
because	O
of	O
increased	O
controllability	O
.	O
</s>
<s>
Spin-on	O
glass	O
or	O
spin-on	O
dopant	O
doping	B-Algorithm
is	O
a	O
two-step	O
process	O
of	O
applying	O
a	O
mixture	O
of	O
SiO2	O
and	O
dopants	O
(	O
in	O
a	O
solvent	O
)	O
onto	O
a	O
wafer	B-Architecture
surface	O
by	O
spin-coating	O
and	O
then	O
stripping	O
it	O
and	O
baking	O
it	O
at	O
a	O
certain	O
temperatue	O
in	O
the	O
furnace	O
at	O
constant	O
nitrogen+oxygen	O
flow	O
.	O
</s>
<s>
Neutron	O
transmutation	O
doping	B-Algorithm
(	O
NTD	O
)	O
is	O
an	O
unusual	O
doping	B-Algorithm
method	O
for	O
special	O
applications	O
.	O
</s>
<s>
Most	O
commonly	O
,	O
it	O
is	O
used	O
to	O
dope	O
silicon	O
n-type	O
in	O
high-power	O
electronics	O
and	O
semiconductor	B-Algorithm
detectors	I-Algorithm
.	O
</s>
<s>
It	O
is	O
based	O
on	O
the	O
conversion	O
of	O
the	O
Si-30	O
isotope	O
into	O
phosphorus	O
atom	B-Language
by	O
neutron	O
absorption	O
as	O
follows	O
:	O
</s>
<s>
As	O
neutrons	O
continue	O
to	O
pass	O
through	O
the	O
silicon	O
,	O
more	O
and	O
more	O
phosphorus	O
atoms	O
are	O
produced	O
by	O
transmutation	O
,	O
and	O
therefore	O
the	O
doping	B-Algorithm
becomes	O
more	O
and	O
more	O
strongly	O
n-type	O
.	O
</s>
<s>
NTD	O
is	O
a	O
far	O
less	O
common	O
doping	B-Algorithm
method	O
than	O
diffusion	O
or	O
ion	O
implantation	O
,	O
but	O
it	O
has	O
the	O
advantage	O
of	O
creating	O
an	O
extremely	O
uniform	O
dopant	O
distribution	O
.	O
</s>
<s>
Phosphorus	O
is	O
typically	O
used	O
for	O
bulk-doping	O
of	O
silicon	B-Architecture
wafers	I-Architecture
,	O
while	O
arsenic	O
is	O
used	O
to	O
diffuse	O
junctions	O
,	O
because	O
it	O
diffuses	O
more	O
slowly	O
than	O
phosphorus	O
and	O
is	O
thus	O
more	O
controllable	O
.	O
</s>
<s>
By	O
doping	B-Algorithm
pure	O
silicon	O
with	O
Group	O
V	O
elements	O
such	O
as	O
phosphorus	O
,	O
extra	O
valence	O
electrons	O
are	O
added	O
that	O
become	O
unbounded	O
from	O
individual	O
atoms	O
and	O
allow	O
the	O
compound	O
to	O
be	O
an	O
electrically	O
conductive	O
n-type	O
semiconductor	O
.	O
</s>
<s>
Doping	B-Algorithm
with	O
Group	O
III	O
elements	O
,	O
which	O
are	O
missing	O
the	O
fourth	O
valence	O
electron	O
,	O
creates	O
"	O
broken	O
bonds	O
"	O
(	O
holes	O
)	O
in	O
the	O
silicon	O
lattice	O
that	O
are	O
free	O
to	O
move	O
.	O
</s>
<s>
Such	O
effect	O
is	O
used	O
for	O
instance	O
in	O
sensistors	B-Algorithm
.	O
</s>
<s>
Lower	O
dosage	O
of	O
doping	B-Algorithm
is	O
used	O
in	O
other	O
types	O
(	O
NTC	O
or	O
PTC	O
)	O
thermistors	O
.	O
</s>
<s>
Common	O
in	O
CMOS	B-Device
technology	O
.	O
</s>
<s>
Gallium	O
is	O
a	O
dopant	O
used	O
for	O
long-wavelength	O
infrared	O
photoconduction	O
silicon	B-Algorithm
detectors	I-Algorithm
in	O
the	O
8	O
–	O
14	O
μm	O
atmospheric	O
window	O
.	O
</s>
<s>
Gallium-doped	O
silicon	O
is	O
also	O
promising	O
for	O
solar	O
cells	O
,	O
due	O
to	O
its	O
long	O
minority	O
carrier	O
lifetime	O
with	O
no	O
lifetime	O
degradation	O
;	O
as	O
such	O
it	O
is	O
gaining	O
importance	O
as	O
a	O
replacement	O
of	O
boron	O
doped	O
substrates	B-Architecture
for	O
solar	O
cell	O
applications	O
.	O
</s>
<s>
Indium	O
is	O
a	O
dopant	O
used	O
for	O
long-wavelength	O
infrared	O
photoconduction	O
silicon	B-Algorithm
detectors	I-Algorithm
in	O
the	O
3	O
–	O
5	O
μm	O
atmospheric	O
window	O
.	O
</s>
<s>
It	O
diffuses	O
fast	O
,	O
so	O
is	O
usually	O
used	O
for	O
bulk	O
doping	B-Algorithm
,	O
or	O
for	O
well	O
formation	O
.	O
</s>
<s>
Bulk	O
doping	B-Algorithm
can	O
be	O
achieved	O
by	O
nuclear	O
transmutation	O
,	O
by	O
irradiation	O
of	O
pure	O
silicon	O
with	O
neutrons	O
in	O
a	O
nuclear	O
reactor	O
.	O
</s>
<s>
Heavy	O
doping	B-Algorithm
with	O
antimony	O
is	O
important	O
for	O
power	O
devices	O
.	O
</s>
<s>
Heavily	O
antimony-doped	O
silicon	O
has	O
lower	O
concentration	O
of	O
oxygen	O
impurities	O
;	O
minimal	O
autodoping	O
effects	O
make	O
it	O
suitable	O
for	O
epitaxial	O
substrates	B-Architecture
.	O
</s>
<s>
Bismuth	O
is	O
a	O
promising	O
dopant	O
for	O
long-wavelength	O
infrared	O
photoconduction	O
silicon	B-Algorithm
detectors	I-Algorithm
,	O
a	O
viable	O
n-type	O
alternative	O
to	O
the	O
p-type	O
gallium-doped	O
material	O
.	O
</s>
<s>
Lithium	O
is	O
used	O
for	O
doping	B-Algorithm
silicon	O
for	O
radiation	O
hardened	O
solar	O
cells	O
.	O
</s>
<s>
Germanium	O
bulk	O
doping	B-Algorithm
suppresses	O
large	O
void	O
defects	O
,	O
increases	O
internal	O
gettering	O
,	O
and	O
improves	O
wafer	B-Architecture
mechanical	O
strength	O
.	O
</s>
<s>
Silicon	O
,	O
germanium	O
and	O
xenon	O
can	O
be	O
used	O
as	O
ion	O
beams	O
for	O
pre-amorphization	O
of	O
silicon	B-Architecture
wafer	I-Architecture
surfaces	O
.	O
</s>
<s>
Gold	O
introduces	O
a	O
donor	B-Algorithm
level	I-Algorithm
0.35	O
eV	O
above	O
the	O
valence	O
band	O
and	O
an	O
acceptor	B-Algorithm
level	I-Algorithm
0.54	O
eV	O
below	O
the	O
conduction	O
band	O
.	O
</s>
<s>
Platinum	O
introduces	O
a	O
donor	B-Algorithm
level	I-Algorithm
also	O
at	O
0.35	O
eV	O
above	O
the	O
valence	O
band	O
,	O
but	O
its	O
acceptor	B-Algorithm
level	I-Algorithm
is	O
only	O
0.26	O
eV	O
below	O
conduction	O
band	O
;	O
as	O
the	O
acceptor	B-Algorithm
level	I-Algorithm
in	O
n-type	O
silicon	O
is	O
shallower	O
,	O
the	O
space	O
charge	O
generation	O
rate	O
is	O
lower	O
and	O
therefore	O
the	O
leakage	O
current	O
is	O
also	O
lower	O
than	O
for	O
gold	O
doping	B-Algorithm
.	O
</s>
<s>
If	O
an	O
equal	O
number	O
of	O
donors	O
and	O
acceptors	O
are	O
present	O
in	O
the	O
semiconductor	O
,	O
the	O
extra	O
core	O
electrons	O
provided	O
by	O
the	O
former	O
will	O
be	O
used	O
to	O
satisfy	O
the	O
broken	O
bonds	O
due	O
to	O
the	O
latter	O
,	O
so	O
that	O
doping	B-Algorithm
produces	O
no	O
free	O
carriers	O
of	O
either	O
type	O
.	O
</s>
<s>
Conductive	B-Algorithm
polymers	I-Algorithm
can	O
be	O
doped	O
by	O
adding	O
chemical	O
reactants	O
to	O
oxidize	O
,	O
or	O
sometimes	O
reduce	O
,	O
the	O
system	O
so	O
that	O
electrons	O
are	O
pushed	O
into	O
the	O
conducting	O
orbitals	O
within	O
the	O
already	O
potentially	O
conducting	O
system	O
.	O
</s>
<s>
There	O
are	O
two	O
primary	O
methods	O
of	O
doping	B-Algorithm
a	O
conductive	B-Algorithm
polymer	I-Algorithm
,	O
both	O
of	O
which	O
use	O
an	O
oxidation-reduction	O
(	O
i.e.	O
,	O
redox	B-Operating_System
)	O
process	O
.	O
</s>
<s>
Chemical	B-Algorithm
doping	I-Algorithm
involves	O
exposing	O
a	O
polymer	O
such	O
as	O
melanin	O
,	O
typically	O
a	O
thin	O
film	O
,	O
to	O
an	O
oxidant	O
such	O
as	O
iodine	O
or	O
bromine	O
.	O
</s>
<s>
Electrochemical	O
doping	B-Algorithm
involves	O
suspending	O
a	O
polymer-coated	O
,	O
working	O
electrode	O
in	O
an	O
electrolyte	O
solution	O
in	O
which	O
the	O
polymer	O
is	O
insoluble	O
along	O
with	O
separate	O
counter	O
and	O
reference	O
electrodes	O
.	O
</s>
<s>
An	O
electric	O
potential	O
difference	O
is	O
created	O
between	O
the	O
electrodes	O
that	O
causes	O
a	O
charge	O
and	O
the	O
appropriate	O
counter	O
ion	O
from	O
the	O
electrolyte	O
to	O
enter	O
the	O
polymer	O
in	O
the	O
form	O
of	O
electron	O
addition	O
(	O
i.e.	O
,	O
n-doping	O
)	O
or	O
removal	O
(	O
i.e.	O
,	O
p-doping	B-Algorithm
)	O
.	O
</s>
<s>
N-doping	O
is	O
much	O
less	O
common	O
because	O
the	O
Earth	O
's	O
atmosphere	O
is	O
oxygen-rich	O
,	O
thus	O
creating	O
an	O
oxidizing	O
environment	O
.	O
</s>
<s>
Thus	O
,	O
chemical	O
n-doping	O
must	O
be	O
performed	O
in	O
an	O
environment	O
of	O
inert	O
gas	O
(	O
e.g.	O
,	O
argon	O
)	O
.	O
</s>
<s>
Electrochemical	O
n-doping	O
is	O
far	O
more	O
common	O
in	O
research	O
,	O
because	O
it	O
is	O
easier	O
to	O
exclude	O
oxygen	O
from	O
a	O
solvent	O
in	O
a	O
sealed	O
flask	O
.	O
</s>
<s>
However	O
,	O
it	O
is	O
unlikely	O
that	O
n-doped	O
conductive	B-Algorithm
polymers	I-Algorithm
are	O
available	O
commercially	O
.	O
</s>
<s>
Molecular	O
dopants	O
are	O
preferred	O
in	O
doping	B-Algorithm
molecular	O
semiconductors	O
due	O
to	O
their	O
compatibilities	O
of	O
processing	O
with	O
the	O
host	O
,	O
that	O
is	O
,	O
similar	O
evaporation	O
temperatures	O
or	O
controllable	O
solubility	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
relatively	O
large	O
sizes	O
of	O
molecular	O
dopants	O
compared	O
with	O
those	O
of	O
metal	O
ion	O
dopants	O
(	O
such	O
as	O
Li+	O
and	O
Mo6+	O
)	O
are	O
generally	O
beneficial	O
,	O
yielding	O
excellent	O
spatial	O
confinement	O
for	O
use	O
in	O
multilayer	O
structures	O
,	O
such	O
as	O
OLEDs	B-Device
and	O
Organic	O
solar	O
cells	O
.	O
</s>
<s>
However	O
,	O
similar	O
to	O
the	O
problem	O
encountered	O
in	O
doping	B-Algorithm
conductive	B-Algorithm
polymers	I-Algorithm
,	O
air-stable	O
n-dopants	O
suitable	O
for	O
materials	O
with	O
low	O
electron	O
affinity	O
(	O
EA	O
)	O
are	O
still	O
elusive	O
.	O
</s>
<s>
Recently	O
,	O
photoactivation	O
with	O
a	O
combination	O
of	O
cleavable	O
dimeric	O
dopants	O
,	O
such	O
as	O
[RuCp∗Mes]2,	O
suggests	O
a	O
new	O
path	O
to	O
realize	O
effective	O
n-doping	O
in	O
low-EA	O
materials	O
.	O
</s>
<s>
Research	O
on	O
magnetic	O
doping	B-Algorithm
has	O
shown	O
that	O
considerable	O
alteration	O
of	O
certain	O
properties	O
such	O
as	O
specific	O
heat	O
may	O
be	O
affected	O
by	O
small	O
concentrations	O
of	O
an	O
impurity	O
;	O
for	O
example	O
,	O
dopant	O
impurities	O
in	O
semiconducting	O
ferromagnetic	O
alloys	O
can	O
generate	O
different	O
properties	O
as	O
first	O
predicted	O
by	O
White	O
,	O
Hogan	O
,	O
Suhl	O
and	O
Nakamura	O
.	O
</s>
<s>
Electrons	O
or	O
holes	O
introduced	O
by	O
doping	B-Algorithm
are	O
mobile	O
,	O
and	O
can	O
be	O
spatially	O
separated	O
from	O
dopant	O
atoms	O
they	O
have	O
dissociated	O
from	O
.	O
</s>
<s>
This	O
technique	O
is	O
called	O
modulation	B-Algorithm
doping	I-Algorithm
and	O
is	O
advantageous	O
owing	O
to	O
suppressed	O
carrier-donor	O
scattering	O
,	O
allowing	O
very	O
high	O
mobility	O
to	O
be	O
attained	O
.	O
</s>
