Discuss the formulation of energy band for single electron atom or hydrogen atom.

1. What is Solid State Device?

Answer:  Electronic device in which electricity flows through solid semiconductor crystals ( Silicon, Gallium, Arsenide, Germanium) rather then though vacuum bobs. 

2.Semiconductor in Equilibrium

         • Energy bands,

         • Intrinsic and Extrinsic Semiconductor,

         • Fermi levels,

         • Electron and Hole concentrations,

         • Temperature Dependence of Carrier concentrations and Invariance of  Fermi level.

3. Define Wave Function.

Answer: Wave function is define as the probability of finding particular at a particular position at a particular instance of time. 

 Wave function is a complex function and donated as Ψ,

                                Ψ =A+iB

As it a complex function  I Ψ l  will give the real value at position,

                       l Ψ l² = Ψ. Ψ^*

                                 =(A+iB)(A-iB)

                                =A²-(iB)²

                                =A²-i².B²

                                     =A²+B²

4. Discuss the formulation of energy band for single electron atom or hydrogen atom.

Ans: The formulation of energy band for single electron atom or hydrogen atom.

Figure a shows the radial probability density function for the lowest electron energy state of the single, noninteracting hydrogen atom, and Figure b shows the same probability curves for two atoms that are in close proximity to each other. The wave functions of the electrons of the two atoms overlap, which means that the two electrons will interact. This interaction or perturbation results in the discrete quan- tized energy level splitting into two discrete energy levels, schematically shown in Figure c. The splitting of the discrete state into two states is consistent with the Pauli exclusion principle.

since no two electrons can have the same quantum number, the discrete energy must split into a band of energies in order that each electron can occupy a distinct quantum state.

5. Define the Fermi Level.

Answer: The highest energy level that an electron can occupy at absolute zero temperature is known as the Fermi level. The Fermi level is located between the valence band and the conduction band as the electrons are in the lowest energy state at absolute zero temperature.

6. Classification of materials based on Energy band

Answer: 

• Based on the ability of various materials to conduct current, the materials are classified as conductors,                 insulators and the semiconductors.

• A metal which is very good carrier of electricity is called conductor. The copper and Aluminum are                 good examples of a conductor.

• A very poor conductor of electricity is termed as insulator. The glass, wood, mica, diamond are the                 examples of an insulator.

• A metal having conductivity which is between conductors and insulators is called Semiconductor.

• The silicon and germanium are the examples of semiconductors. This does not conduct current at low                 temperatures but as temperature increases these materials behave as good conductors.