Understanding Semiconductor diodes

Understanding Semiconductor diodes

1. Conductors are materials which allow current to flow through them easily. This is because conductors have free electrons which can drift between their atoms.
2. Insulators are materials which do not conduct electrical current.
3. Semiconductor is a material whose resistance is between those of good conductors and those of good insulators.


1. The conductivity of a semiconductor can be increased by adding a small amount of certain substances (impurities).
2. DOPING is the process of adding a small amount of impurities into the crystalline lattice of semiconductors.


1. There are 2 types of semiconductors: p-type and n-type.
2. p-type semiconductor:
i. the holes (positive charge) are the majority carriers.
ii. The trivalent atoms are called acceptor atoms because they accept any free electrons to fill the holes.
iii. E.g. boron, indium and gallium.
3. n-type semiconductor:
i. the free electrons (negative charge) are the majority carriers.
ii. The pentavalent atoms are called donor atoms because they supply free electrons.

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