An excellent question! In short, the electronic
properties (particularly the electrical
conductivity) of semiconductors can be engineered
and controlled. See below for the more materials
You've probably learned that metals conduct
electricity easily, semiconductors less easily,
and insulators not at all. This is partially
true, but it really depends on the temperature and
even the material you are talking about. Most of
the time we talk about room temperature because
that's the temperature we and our computers
operate in. However, it's possible to make a
semiconductor conduct electricity or a metal turn
into an insulator depending on the temperature.
The most basic level a computer processes
information is in binary (long strings
of 0's and 1's). This system of 0's and 1's is
encoded in the hardware of the computer as no
current (== 0) or some current (==1). This also
works with voltages, polarized light, magnetism,
or any signal/material property that can have two
Semiconductors are the basis of many electronic
devices because we can control the electronic
conductivity (specifically around room
temperature). Silicon has been the material of
choice, mostly because it is cheap, abundant, and
has good enough electronic properties, though
there is active research in looking for alternate
semiconducting materials. We control the
conductivity via doping, or intentionally
Depending on the impurity incorporated, the
resulting semiconductor is called either p-type
or n-type. The naming is based on if the
carriers responsible for the conductivity are
electrons or holes (which can be thought of
as the lack of an electron).
In materials science, we have a more stringent
definition for whether a material is a metal,
semiconductor, or insulator based on whether or
not it has a band gap. When we talk about material
properties, we are mostly concerned with
electrons and the energy levels they can live
in. In metals, there is overlap between the
energy levels with electrons and those without.
This is basically the physics for why electrons
are able to conduct so easily in metals.
In semiconductors and insulators, there is a
range of energies for which no electrons can
exist, aka a band gap. Semiconductors have
smaller band gaps compared to insulators.
Electrons can jump over the gap with sufficient
amount of energy. This can be thermal (i.e., heat)
or electromagnetic (i.e., light). For an
here . For any practical purposes, you
can't really "turn off" the conductivity in a
metal, and the amount of energy to make insulators
conductive is too high.
For silicon, the p-type or n-type doping
introduces carriers that can conduct at room
temperature. The main unit for most electronic
devices is the p-n junction , which consists
of putting p-type silicon together with n-type
silicon into once device. This configuration lets
you control current depending on the bias voltage
you put on the device. Other electronic elements
like the transistor, LED, solar cells are simply
more complicated designs, but all operate using
the same principles as the pn-junction. More info
here on the
if you're curious.
Hope this helps!
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