3.11 Light Emitting Diode
2/16
A. Homojunction
1.
Fermi level E aligns from p- to n-type.
F
2.
Depletion region appear from p- to n-type, W > W if N < N .
p
n
A
D
3.
Built in voltage V
(V ) becomes a barrier.
bi
o
4.
Barrier lowers with forward bias V and becomes V ­ V .
bi
5.
When carriers cross the barrier, spontaneous emission happens.
Mainly emits in p-type
Generation in p-type or n-type again

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