What is a semiconductor | What are the types of semiconductor
This page mentions semiconductor definition and describes different types of semiconductor and materials used in semiconductor.
What is a semiconductor?
They are materials whose electrical properties lie between conductors and insulators.
For example: Silicon and Germanium
Conductivity of insulators, semiconductors and conductors are as follows.
Semiconductor materials
Semiconductor materials are categorized as follows. The same have been shown in the periodic table of elements.
• Elemental semiconductors include Si and Ge. They compose of single species of atoms.
• Compound semiconductors include combinations of atoms of column
III and column V and some atoms from column II and VI. Combinations of two atoms
result in binary compounds.
• There are three element (Ternary) compounds e.g. GaAsP and
four element (quaternary) compounds e.g. InGaAsP.
• The wide variety of electronic and optical properties of these semiconductors provides the
device engineer with great flexibility in the design of electronic and opto-electronic functions.
• Ge was widely used in the early days of semiconductor development for transistors and diodes.
• Si is now used for the majority of rectifiers, transistors and integrated circuits.
• Compounds are widely used in high-speed devices and devices requiring the emission or absorption of light.
• The electronic and optical properties of semiconductors are strongly affected by impurities,
which may be added in precisely controlled amounts (e.g. an impurity concentration of one part
per million can change a sample of Si from a poor conductor to a good conductor of electric current).
This process called doping.
| Semiconductor material | Symbol | Atomic Number | Benefits |
|---|---|---|---|
| Carbon | C | 6 | • Very expensive • Band gap large: 6eV • Difficult to produce without high contamination |
| Silicon | Si | 14 | • Cheap • Ultra High purity • Oxide is amazingly perfect for ICs |
| Germanium | Ge | 32 | • High mobility • High purity material • Oxide is porous to water/hydrogen |
| Tin | Sn | 50 | • Only "white tin" is a semiconductor. • Converts to metallic form under moderate heat |
| Lead | Pb | 82 | • Only "White lead" is a semiconductor • Converts to metallic form under moderate heat |
Types of Semiconductor
There are two main types of semiconductor viz. intrinsic and extrinsic.
➤Intrinsic semiconductor: A semiconductor in which there is a balance between the number of electrons in the
conduction band and the number of holes in the valence band is called an intrinsic semiconductor.
Examples: pure carbon and germanium
➤Extrinsic semiconductor Semiconductor material added with other element is known as extrinsic semiconductor.
For example, N-type and P-type materials.
P-type material:
When a trivalent element(e.g. indium, gallium) is added to tetravalent semiconductor
( germanium or silicon) then a deficit of electron is produced for each impurity atom;
such type of material is known as P-type material.
Example: Doping silicon or germanium with phosphorus (having five valence electrons).
N-type material:
When a pentavalent element (e.g. arsenic, antimony) is added to tetravalent semiconductor, then
a surplus electron is produced by each impurity atom; such type of material is known as
N-type material.
Example: Doping silicon or germanium with boron (having three valence electrons).
What is difference between
BJT vs FET
Diac vs Triac
JUGFET vs MOSFET
LED vs Laser
Photo Diode vs Photo Transistor
Halfwave rectifier vs Fullwave rectifier
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