n-Type Semiconductor, p-Type Semiconductor, Intrinsic, Extrensic
n-Type Semiconductor :-
When a small amount of pentavalent impurity is added to a pure semiconductor, it is called n-type semiconductor. Such an impurity is called donor impurity.
Ex. Arsenic, bismuth, phosphorous and antimony.
For every donor dopant atom (Nd) near the conduction band, there is another free electron (n)
NOTE no change in T is needed as for metals.
Unlike for intrinsic semiconductors, free electron doesn’t leave a mobile free hole behind. Instead, any holes are trapped in donor state and thus will not contribute substantially to conductivity as for intrinsic semiconductors (thus p~0).
N-type: A N-type material is one in which electrons are majority charge carriers i.e. they are negatively charged materials (-----)
p-Type Semiconductor :-
When a small amount of trivalent impurity is added to a pure semiconductor, it is called p-type semiconductor. Such an impurity is called acceptor impurity.
Ex. Gallium, boron or indium.
We can do the same thing with “acceptor dopants.”
Every acceptor generates excess mobile holes (p=Na).
Now holes totally outnumber electrons, so conductivity equation switches to p domination.
P-type: A P-type material is one in which holes are majority carriers i.e. they are positively charged materials (++++)
• Intrinsic:
# electrons = # holes (n = p)
--case for pure Si
• Extrinsic:
--n ≠ p
--occurs when DOPANTS are added with a different
# valence electrons than the host (e.g., Si atoms)
Labels: BE, SSD