Fermi Energy Band Diagrams in PMOS and Applications

 Fermi energy band diagrams in PMOS

Modes:

              

a.Accumulation

               b.Turned off 

               c.Depletion 

               d.Inversion

 a.When a positive voltage is applied at the gate terminal of the p type MOSFET, the opposite charged particles i.e electrons are attracted towards the gateoxide.

Due to which there is increase in concentration of majority charge carriers near the oxide. As the doping intensity of n-type particles increase the energy banbends towards the valence band.

b.When there is no gate voltage applied , there is no bending in the fermi energy bands.

c.When a negative voltage is applied at the gate, electrons are repelled away from the region near the gate oxide - semiconductor interface. Hence the net charge near the gate oxide becomes zero.

As the concentration of majority charge carrier lowers the intrinsic fermi energy shifts away from the valence band . The band bend upwards.

d.When the negative voltage at gate is increased beyond the threshold voltage , minority charge carriers i.e holes are attracted near the gate oxide - semiconductor interface.

Due to increase in concentration of holes,the semiconductor acts as an p-type substrate i.e there is inversion of substrate. Hence the intrinsic fermienergy band crosses the Fermi energy at 0k (Ef) and bends upwards.

Applications Of Fermi Level :

1.Fermi Energy levels finds its use in describing properties of metals,insulators and semiconductors.

2.The way fermi energy level depends on factors such as temperature help in determining properties such as conductivity of the semiconductor.

Interesting Research Going On In the field of Fermi Energy:

1.Fermi Energy of Optoelectronic Devices

2.Quantum Size Effects in Ultra-thin Films

3.Fermi Energy of Organic Semiconductors

Author : Sukhanshu Dukare

References:

1. http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/Fermi.html
2. https://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Semiconductors/Fermi_level#Energy_Band_Diagram
3. https://www.physics-and-radio-electronics.com/electronic-devices-and-circuits/semiconductor/extrinsic-semiconductor/fermi-level-in-extrinsic-semiconductor.html
4. https://www.youtube.com/watch?v=OVnVN0vSXn0&list=PLQms29D1RqeKGBEW8La2a7YuN5_4pSV4k