Electron
and hole are the two charge carriers that are present in a semiconductor
material. The electron is the majority carrier in an N-type semiconductor and hole
is the majority carrier in P-type Semiconductor. The N-type and P-type
semiconductors are called as extrinsic semiconductors as these are doped with
the external impurities i.e., P-type has trivalent impurities while N-type has
penta-valent impurities. The intrinsic semiconductor (pure form of
semiconductor) is doped with impurities to form P type and N type
semiconductors. The intrinsic semiconductor is said to behave as an Insulator
at absolute zero (0 deg c). The electron and hole have same mass and charge but
electron has negative charge while hole has positive charge.
- Electron is negatively charged and its value is given as 1.6022 x 10-19 Coulomb.
- Hole is positively charged and its value is given as 1.6022 x 10-19 Coulomb.
- Mass of electron and hole: 9.1 x 10-31 kg.
A hole is said to be absence of electron
in the valence band, then how will a physically non existing element have mass
and charge. This can be understood as follows. Consider the diagram below in
the valence band of a P-Type semiconductor.
Assume
semiconductor at room temperature there will be continuous breakdown and
creation of covalent bonds in the valence band which is generation and
recombination of electrons and holes consider a bond breakage takes place and
electron will move from one location and occupy another vacant location in the
valence band as follows. In the series of diagrams the location of electron
moving from right to left can be seen which resembles as if a hole is moving
from left to right.
From
the above series of diagrams an electron movement in the valence band is
considered as hole movement in opposite direction and thus a physically non
existing material has mass and charge. In semiconductor materials hole is always considered on valence band and electron is always considered in conduction band.
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