How do semiconductors work? (with animation) | Intermediate Electronics


Today, we are going to discuss the
basics of semiconductors and their role in the field of electronics. Before semiconductor devices even existed,
vacuum tubes were the only devices available for signal amplification,
switching and other applications. Though vacuum tubes are functional,
they’re bulky, require a high operating voltage
and are completely inefficient. When semiconductor devices like
transistors were invented, semiconductors started to acquire a dominating
role in electronics. Semiconductors are materials that are in
between conductors and insulators when it comes to the ability to conduct electrical current,
which explains the name, semiconductors. The most commonly used semiconductor
material in the electronics industry is silicon. After that, it’s a compound known asgallium arsenide. Semiconductor materials have two
current carriers, free electrons and holes. In an intrinsic semiconductor material,
free electrons are produced when the material receives sufficient
thermal energy that provides valence electrons from
the valence band enough energy to jump to the conduction
band and turn it into free electrons. When valence electrons jump
to the conduction band, they leave vacancies in the valence band. And these vacancies are called holes. The number of holes in the valence band
is just equal to the number of free electrons in the conduction band
in this undoped, intrinsic material. A semiconductor material becomes
a useful electronic component by controlling its conductivity. However, semiconductor materials,
in their intrinsic state, do not conduct current well. This is because of the limited number
of free electrons and holes in it. But through a process known as doping,
the conductivity of a semiconductor can be increased. Doping increases the number of current
carriers by adding impurities with either more free electrons or free holes
to the intrinsic semiconductor material. The number of free electrons in an
intrinsic semiconductor material is increased in the doping process
by adding pentavalent impurity atoms or atoms with five valence electrons
such as arsenic, phosphorus, bismuth, or antimony. To visualize this, let’s examine an
antimony atom covalently bonded with four adjacent silicon atoms. As we can see, only four valence electrons
of the antimony atom are used to form covalent bonds with the silicon atoms,
leaving an extra electron that becomes a free electron. So by adding pentavalent impurity atoms
to an intrinsic semiconductor material, the number of free electrons
can be increased as well as the conductivity of the
semiconductor material. Semiconductors doped with pentavalent
atoms are N-type semiconductors since the majority of its current
carriers are electrons. In order for an intrinsic semiconductor
material to have more holes, they are doped with trivalent
impurity atoms. These are atoms with three valence
electrons in their valence shell like boron, indium, and gallium. To understand how trivalent impurity atoms
increase the number of holes in an intrinsic semiconductor material,
let’s see a boron atom form covalent bonds with four
adjacent silicon atoms. In this case, when the boron covalently bonds with the four silicon atoms, a hole is produced. This is because, each of the four silicon
atoms requires one electron from the boron atom, but it only
has three valence electrons. In this case, we can say that by adding
more trivalent impurity atoms to an intrinsic semiconductor material,
it increases the number of holes and improves the conductivity of
the semiconductor material. Semiconductors doped with trivalent
atoms are P-type semiconductors since the majority of its current
carriers are holes. The doping process converts an intrinsic
semiconductor material into extrinsic and produces either an N-type or a P-type
semiconductor material. Combining the N-type and P-type
semiconductor materials, creates a boundary known as P-N junction. This P-N junction is the basis for different
semiconductor devices widely used today like diodes, transistors, and thyristors. In this video, we talked about the
basics of semiconductors, the intrinsic semiconductor and
its poor conductivity, how doping increases the number
of current carriers in a semiconductor material and
improves its conductivity. We also briefly mentioned how different
semiconductor devices were created based on the P-N junction. If you have any questions,
leave it in the comments below. And if you’ve found this interesting
or helpful Please subscribe to our channel
and like this video!

3 comments on “How do semiconductors work? (with animation) | Intermediate Electronics”

  1. Ingrid Vos says:

    The element Boron is represented by B, not by Bo

  2. Soulimane Mammar says:

    Great videos…Thanks a lot

  3. NAIDHILA BINTI JUNAIDI - says:

    You explain better than my lecturer. Thank you

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