Structural Properties of Semiconductors.
Structural properties of semiconductors -we know that the basic elements of an atom are three
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- Electrons
- Protons
- Neutrons
From the Bohr model, we see that the protons and
neutrons in the center of the atom are called nuclei in one of them and the
electrons are rotating in a fixed orbit around it.
In the upper chi, the silicon bore model has 14
electrons and germanium have 32 electrons. The last orbits of silicon and
germanium have four electrons each. The electrons in this last orbit are called
Valance Electrons.
The energy required to move these electrons is comparatively
less than that of other electrons.
I have known about an atom for so long but if it is a
silicon or germanium crystal then what will be the structure?
In pure silicon or germanium crystals, four valance
electrons are bonded to each other. The formation of a bond between electron
shares in this way is called a covalent bond.
We know that covalent bonds have
no free electrons. How will electricity flow if there are no free electrons?
Although the covalent bond is strong when the required kinetic energy is
received from an external source, the bond is broken and the electrons are
released.
Now let's talk about energy levels.
We know that the molecular structure of solid, liquid,
and gaseous substances is different. Particles are very far apart in the field
of gaseous matter.
Some are close to the liquid field and some are close to the
solid field. We know from the Bohr model that every energy level of an atom has
a value of energy.
The energy level of electrons located at different
energy levels of an atom is expressed through Chi which is called Energy Level
Diagram or Energy Band Diagram.
When a whole crystal moves in the place of an
atom, the energy levels are called energy bands.
Conduction Band
When free electrons conduct electricity to a
substance, they are called conduction electrons. The band in which these
electrons move is called the conduction band.
Forbidden Gap
There are some gaps in the middle of one band after
another. These are called Forbidden Gap.
There are no electrons here. More
space between the two bands means more energy is needed to transfer the
electrons in the v-lens band.
Valance Band
The electrons in the last orbit of an atom are called
valence electrons. The band in which these electrons move is called the v-lens
band.
The electrons in this bond are released when they get enough energy to
reach the conduction band and conduct electricity.
Semiconductor
A certain amount of electricity flows through a semiconductor. The valence band is fairly full of valence electrons while the
conduction band has no electrons. The amount of space between the v-lens band
and the conduction band is very small.
It is almost equal to (1 eV). When a small amount of external energy is given, the electron is released and enters
the conduction band, resulting in an electric current.
Conductor
Electricity can flow through a conductive substance
because the conduction band of a conductive substance contains a large number
of free electrons.
From the upper chi, it can be seen that there is no space
between the v-lens and the conduction band.
Insulator
No electricity flows through the non-conductive
material, because the conduction band of the non-conductive material has no
free electrons.
From the upper chi, the amount of space between the vane-lens
and the conduction band in the field of non-conductive matter is much greater
than (15 eV). So a lot of energy is needed to release electrons.