If an element with
five valence electrons,
like phosphorus,
is mixed in with a
siliconcrystal...
...the phosphorus
and silicon bond,
and one valence
electron escapes.
It becomes a
fr electron,
right?
Fr electron
That's right!
This causes the
electricalconductivity
of this semiconductor
toincrease.
This semiconductor
is caed an n-type
semiconductor
because the electron,
which has a negative
electrical property,
becomes a caier
ofelectricity.
What's
this n ?
...What's
wrong?
The n stands
for negative.
Ah...!
Negative
Silicon
Phosphorus
Silicon
Silicon
Phosphorus
Sigh...
166 Chapter 5 How Can You Conveniently Use Electricity?
Now, let's say we
mixed in a lile of the
element boron, which
has thr valence
electrons.
The boron and silicon
bond, but there is an
empty seat left in the
space that doesn't have
an electron.
Empty seat?
This empty
seat iscaed
a hole.
Holes are places
electrons are
vacant in covalent
bonds.
You can think
ofthe hole as
a fr electron
with a positive
charge.
Okay...
Boron
Hole
Hole
Drift
Drift
Hole
Hole
Semiconductors 167
Therefore,
electrical
conductivity also
increases for this
semiconductor.
This kind of
semiconductor is caed
a p-type semiconductor
because the hole, which
has a positive electrical
property, becomes a
caier of electricity.
What's the p
stand for?
What's the
oosite of
negative?
Oosite...
!!
The p stands for
positive, right?
Right!
The substance
formed by mixing
an element such
as phosphorus or
boron into a pure
silicon crystal is
caed an extrinsic
semiconductor.
I get it!
Electricity
n-type P-type
Extrinsic semiconductor
168 Chapter 5 How Can You Conveniently Use Electricity?

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