Quantum Physics
To study this - we will review
- Simple quantum mechanics
- Energy band theory
- Density of states for carriers
- Recombination and generation of carriers
- Carrier transport
Quantum Theory
Started in 1901 when Max Planck explained blackbody radiation.
Solid objects emit radiation when heated.
Black body radiation curves showing peak wavelengths at various temperatures:-
For more insight, play with Java Applets of Black body radiation from the following links:
- http://www.lon-capa.org/~mmp/applist/blackbody/ black.htm
- http://webphsics.davidson.edu/alummi/MiLee/java/_mjl.htm
Many attempts were made to explain the Black Body radiation pattern i.e, Rayliegh-Jeans, Wiens.
Finally Planck solved it.
Vibrating atoms in material could only radiate or absorb energy in discrete packets.
For a given atomic oscillator vibration at a frequency  Hz. Planck postulated that the energy of the oscillator was restricted to quantized values.
 and  is the circular frequency
h = Planck's constant = 
One quantum of energy  , where  = Wavelength (m) and 'c' is the velocity of light in free space.
Bohr's theory of atoms
To explain why atoms when energized (heat, electric discharge) emit discrete spectral lines  , i = integer as shown in Fig.1.7
Bohr said that electrons in an atom move in well defined orbits, each orbit has a fixed energy level and angular momentum.
Hydrogen atoms, atomic No. = 1, and has only one electron
Angular momentum of this atom
 = electron rest mass,  = linear electron velocity
 = radius of the orbit for a given n
Now at equilibrium, centrifugal force = electric force
Total energy
Light energy emitted by a Hydrogen atom when heated or excited
discrete in nature and equal to
as shown in Fig .1.8
|
for n th orbit 
