Before the advent of semiconductors, all solids were divided into two groups. They are conductors and insulators.
Conductors:
The basic definition of conductor is which metal have very low resistance called conductors. Example of conductors is aluminum which is most repeatedly used, has a very low resistivity of about 10-6Ω-cm at room temperature.
Insulators:
The basic definition of insulators is which material have very high resistance called insulators. Ex: Silicon do oxide has a very high resistivity of about 1016Ω-cm.The resistivity of conductors lies below 10-2Ω whereas the materials having resistivity greater than 105Ω-cm are called insulators.
A new class of materials was found which could not lie in either of these groups. This materials having resistivity in the intermediate region are known as semiconductors. It is also called as half conductors. These gradually acquired much important because the resistivity can be varied by design under precise control. It was also found that effect of room temperature on conductivity of conductors and semiconductors is quite opposite. In conductors the conductivity decreases with increase in temperature whereas the conductivity of semiconductor is increasing with temperature. Another important property of semiconductor is sharp increase in conductive by the interlocution of negligibly small amount of certain impurities. Bombardment of semiconductors by a beam of light also casus rapid increase its conductivity because of these types of peculiar prosperities, the semiconductors materials are used in the construction of all solid state electric devices.
Semiconductors:
It is the combination of conductors and insulators. There are classified into 2 types – 1) Intrinsic, 2) extrinsic or doped semiconductors
- Intrinsic Semiconductors: These are very pure in these the properties of crystal determined only by the properties of atoms of the semiconductor material itself.
- Extrinsic Semiconductors: If an extremely small (approximately 1 in 108 atoms) carefully controlled amount of an impurity element (generally trivalent or pentavalent atoms) is introduce into the intrinsic semiconductors, say Ge, each of the impurity atom take the place of one of the Ge atoms in the lattice. Since the impurities atoms are very small in number as compare to the Ge atoms, it can be assumed the lattice remains undisturbed and that each impurity atom is surrounded by four Ge atoms. This process of introducing impurity atoms into intrinsic semiconductors are known as doping and the crystals thus obtained is called doped or extrinsic semiconductors.
These extrinsic semiconductors are of two types.
1. N-Type Semiconductors: If the doping is done by any pentavalent substance belonging to group V of the periodic table of the elements (arsenic, antimony or phosphors ) , four valance electrons of the impurity atoms form covalent bonds with four electrons of the Ge atoms and the fifth electrons of the impurity atom becomes free to dander in the lattices since each impurity atom has donated one free electron to the critical these pentavalent impurity is known as donor the crystal is said to be n-type semiconductor as the number of electrons in the crystal is much greater than the number of holes produced by thermal agitation.
2. P-Type Semiconductors: If the doping is done by any trivalent substance belonging to group III of the periodic table of the elements (Indium, aluminum or gallium), three valance electrons of the impurity atoms form covalent bonds with the three electrons of neighboring Ge atoms. The fourth covalent bond has a missing electron, thus a hole is introduced for each impurity atom. In p-type semiconductor holes are majority.
The N-type and P-type semiconductors are electrically neutral because each impurity atom is itself .neutral. In n-type semiconductor, the electrons are the majority charge carriers and the holes are the minority charge carriers. In p-type semiconductor, the electrons are the minority charge carriers and the holes are the majority charge carriers.
Electronic Semiconductor Components:
These are of two types – 1. Active components, 2. Passive components
1. Active Components: These devices can be used for the amplification, rectification of energy from one to another.
Example: Transistor, Diode.
For example LED converts electrical energy into light energy.
2. Passive Components: These devices can be used to complete a circuit with voltage and current sources and active components.
Example: Resistor, Capacitor, Inductor and Transformer.
Different Types of Electronic Components Made by Semiconductors:
- Diodes
- Transistors
- Resistor
- Capacitor
- Fuse
- Inductor
Now let us know about the above components briefly.
1. Diodes:
As the name indicates, the semiconductors diode is constructed from a semiconductor material like Ge or Si. The semiconductor is an electronic device which has a high resistance to the flow of current in one direction and a low resistance in opposite direction. These diodes are used widely now days like rectifiers, doubles, limiters, clippers, modulators, demodulators logic gates, etc.
These diodes are consists of p-n junctions formed in either Ge or Si crystals. In order to obtain a p-n junction diode a Si or Ge crystal is doped with donor atoms at one end and acceptor atoms at the other. This semiconductors crystal had both p-type and n-type regions. Free electrons and holes are represented as – and + respectively. Initially, holes are present in the majority to the junction, and electrons in the majority to the right of the junction. These holes and electrons are freely moved randomly in the lattice. Since there are more electrons at left side, there is a density gradient across the junction. Therefore, more holes diffuse to the right of the junction and more electrons diffuse to left side. As a result of the electrons leaving the n-material, donor ions are produced on the n-side of the junction. When these electrons fill holes on the p side of the junction, the acceptor ions are produced. The space occupied between these ions is called space charge region. In this two types of biasing they are forward bias and reverse bias.
Different types of Diodes are P-N junction diode, Zener diode, Avalanche, etc.
2. Resistors:
It offers resistance to flow of current. The two main characteristics of resistor are its Resistance(R) in ohm and power rating (W) in watts. In electronic circuits, the resistors with higher ‘R’ values have lower wattage rating because they have less current. Units are ohms (Ω).
Different types of Resistors are Carbon resistors, Carbon composite type of resistor, Wire wound Resistors, Film type Resistor, Metal film resistor.
For more information about resistors, read the post: Resistors Color Code and Types of Resistors.
3. Fuse:
It can be stated that the fuse is a device used to prevent over heating due to excessive current. This intern protects the insulation of the wire, machine or the appliances from overheating and damage.
4. Capacitors:
Capacitor is another important passive component commonly observed in electrical and electronic circuits. Some time it also called condenser. Basically it is used to store electrical energy (by charging) and to supply this stored energy when required (by discharging). This component has property of strong charge across its two plates; hence it is also named as capacitor. They are available in fixed and variable types; their capacity is measured in units ‘Farad’. Typically they are available in micro Farads. The capacitor utilization is very high in any analog circuit.
Also get an idea about Different Types and Applications of Capacitors.
5. Inductors:
Induced voltage is the result of flux cutting across a conductor. The action can be produced by physical motion of either magnetic field or the conductor. The device which stops the flow of current known as inductor.
Get some more detailed information in the post: Semiconductor Diodes Characteristics
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