A diode is made up of two words i.e., “Di “ means Two, and “Ode “
means Electrodes which means that a device or component has two
electrodes. (i.e., cathode and anode). A diode is an electronic device
having a two-terminal unidirectional power supply. A semiconductor
diode is the first diode that forms in semiconductor electronic devices,
after that there were lots of new innovations takes place. but the most
common diode used is a semiconductor diode.
A p-n junction is known as a Semiconductor Diode. as it conducts only
in one direction therefore it is used for the purpose of rectification. As it
is made of a crystal-like Silicon or Germanium. It is also known as a
crystal diode. the symbol of the diode is as:
Construction of Diode
We know that there are two types of semiconductor materials: Intrinsic
and Extrinsic semiconductors. In intrinsic semiconductors number of
electrons and holes concentration are equal at room temperature. In an
extrinsic semiconductor, impurities are added to the semiconductor to
increase the number of electrons or the number of holes. These
impurities are pentavalent (Arsenic, Antimony, phosphorous) or tri-
valent (boron, indium, aluminium).
A semiconductor diode has two layers. one layer is of p-type and the
other is of n-type semiconductor.
If we add trivalent impurities in a semiconductor (Silicon and
germanium), a greater number of holes are present and it is a positive
charge. therefore this type of layer is known as the p-type layer.
If we add pentavalent impurities in semiconductors (silicon or
germanium), due to excess electrons there is a negative charge.
therefore this type of layer is known as the n-type layer.
Working of Diode
In the N-type region, the majority charge carriers are electrons and the
minority charge carriers are holes. Whereas, In the P-type region, the
majority of charge carriers are holes and negative charge carriers are
electrons. Because of the concentration difference, the diffusion takes
place in majority charge carriers and they recombine with the opposite
charge. It makes a positive or negative ion. they collect near the
junction. and this region is known as the depletion region.
When anode or p-type of the diode is connected with a negative
terminal and n-type or cathode is connected with the positive terminal of
a battery, this type of diode is connected in reverse bias.
when anode or p-type terminal is connected with a positive terminal and
n-type or cathode is connected with the negative terminal of the battery,
this type of diode is connected in forward bias.
Forward Bias
Reverse Bias
Types of Semiconductor Diode
There are different types of semiconductor diodes:-
LED – The term LED is Light Emitting Diode, it is the most useful kind of diode,
when the diode is attached in forwarding bias, the then-current that flows through
the junction produces light.
Zener diode – Zener diode is a type of diode, it allows the flow of current in
forwarding direction, it can also work in the reverse breakdown but in breakdown
condition, Zener diode has an application in voltage regulation, The Zener diode
uses p-n junction in reverse bias mode, to give Zener effect.
Tunnel diode – The tunnel diode is used for microwave application.
Variable capacitance diode – This kind of diode are also called VARICAP diode,
even though the output of variable capacitance can exhibit the general p-n
junction diode but this diode is approved of giving the preferred capacitance
change as they are different type of diode.
Photodiode – This kind of diode that produces current at a certain amount of light
energy falls over it, In the condition of forwarding bias current transfer from p to n,
while in reverse direction photocurrent flow in the reverse direction, there are two
types of photodiode i.e., PN photodiode and PIN photodiode.
Switching diode etc.
Applications of Semiconductor Diode
Applications of semiconductor diode are as follow:
Rectifier diode – Rectifier diode is a kind of diode that is used for the rectification
of alternating current (A.C).
LED – LED is used for emitting an infrared light spectrum.
Zener diode – Zener diode is used for the stabilization of current and voltage in
electronic systems.
Photodiode – works as a photodetector.
Switching diode- which is used for fast switching requirements.
A tunnel diode – A tunnel diode is a special type of diode which is used in the
negative resistance region.