optical emission from semiconductor using energy band structure.

1. Optical Emission
From Semiconductor
Md
Presented
Manzar
By
Nezami

2. Point Of Discussion
Explain with the help of energy band
structure, the process of optical emission from
semiconductor.

3. To allow consideration of semiconductor optical
sources it is necessary to review some of the
properties of semiconductor
materials, especially with regard to p-n junction.

4. semiconductor
Intrinsic Extrinsic

5. Intrinsic Semiconductor: A perfect
semiconductor crystal containing no impurities
and lattice effect.
Extrinsic Semiconductor: A semiconductor
crystal which is made up by the process of
doping, i.e. adding impurity to it.

7. For a semiconductor in thermal equilibrium the
energy level occupation is described by fermi
dirac distribution function.
 Consequently the probability p(E) that an
electron gains sufficient thermal energy at an
absolute temperature T such that it will be found
occupying a particular energy level E, is given by
the fermi-dirac distribution.
 P(E)=1/{1+exp(E-Ef )/kT}

9. • To create an extrinsic semicondutor the material
is doped with impurity atoms which creates
either more free electrons (donor impurity) or
holes(acceptor impurity)

11. The p-n junction diode
The p-n junction diode is formed by creating
adjoining p and n type semiconductor layers in
single crystal.
A thin depletion region is formed at the junction
through carrier recombination.
This establishes a potential barrier between the p
and n type regions which restricts the inter diffusion
of majority carriers from their respective regions.
An external applied voltage form current flow
through the device as they continuously diffuse away
from the interface.
However, this situation in suitable semiconductor
allows carrier recombination with the emission of
light.