Fermi Level and Work Function Quiz: Semiconductor Fundamentals

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Questions and Answers

Where is the Fermi level typically located in a n-type and p-type semiconductor?

Only in the valence band

Between the conduction and valence bands (correct)

Only in the conduction band

Far away from the conduction and valence bands

What is the work function represented as in metals?

ECBM

Фs

Фm (correct)

What is the energy difference between the conduction band minimum and the vacuum energy level?

Work function

Conduction band maximum

Electron affinity (correct)

Fermi level

What is the purpose of the Schottky diode when used as a rectifier contact?

To allow current flow in one direction Signup and view all the answers

What type of semiconductors can form the Schottky contact?

Both n-type and p-type semiconductors Signup and view all the answers

What is the unit of measurement for the work function and electron affinity?

Volts Signup and view all the answers

What is the result of aligning the Fermi energy of the metal and the semiconductor?

Formation of a depletion layer Signup and view all the answers

What is the energy difference between the band edge with majority carriers and the Fermi energy of the metal?

Barrier height Signup and view all the answers

What is the direction of electron transfer under equilibrium condition when a metal and n-type semiconductor are brought together?

From semiconductor to metal Signup and view all the answers

What is the relationship between the work function of semiconductors and the electron affinity?

The work function is related to the electron affinity, conduction band, and Fermi energy Signup and view all the answers

What happens to the electron affinity and metal work function during the contacting process?

They are invariant fundamental properties Signup and view all the answers

What is the purpose of overcoming the Schottky barrier in a metal-semiconductor junction?

To allow electron flow across the diode Signup and view all the answers

What is the primary characteristic of the Schottky barrier?

Schottky barrier height Signup and view all the answers

What prevents further electron flow from the semiconductor conduction band into the metal in an unbiased Schottky diode?

Built-in-potential Signup and view all the answers

In an unbiased Schottky diode, where is the built-in-potential or built-in-voltage primarily present?

In the n-type semiconductor Signup and view all the answers

What is the result of the net loss of electrons in the semiconductor and metal?

A depletion region and a growing barrier Signup and view all the answers

What is the energy required by the free electrons to overcome the barrier in an unbiased Schottky diode?

Energy greater than the built-in-voltage Signup and view all the answers

What is the width of the region over which electrons move into the metal compared to the width inside the n-type semiconductor?

Negligibly thin Signup and view all the answers

Study Notes

Forming an Ideal MS Contact

When a metal and a semiconductor material are brought together, an instant ideal MS contact is formed, resulting in a mismatch of the Fermi energy (EFM) in the metal and the Fermi energy in the semiconductor (EF).
The electron affinity χ and the metal work function ΦM are invariant fundamental properties that remain unaffected by the contacting process.

Schottky Barrier Contact

A Schottky barrier is a depletion layer formed at the junction of a metal and n-type semiconductor.
It is a potential energy barrier formed at the metal-semiconductor junction when the Fermi energy of the metal and the semiconductor are aligned together.
The barrier height ΦB is defined as the energy difference between the band edge with majority carriers and the Fermi energy of the metal.

Equilibrium Condition (VA=0)

Electrons transfer from the semiconductor to the metal due to their greater energy until the equilibrium condition is established.
The net loss of electrons creates a negative charge in the metal and a positive charge in the semiconductor, resulting in a depletion region and a growing barrier at the semiconductor surface.

Characteristics of the Schottky Barrier

The surface potential-energy barrier ΦB is characterized by the Schottky barrier height, which is a function of the metal and the semiconductor: ΦB=ΦM−χ, for n-type semiconductor.
The built-in-potential or built-in-voltage is primarily present inside the n-type semiconductor and prevents further electron flow from the semiconductor conduction band into the metal.