Quantum Effects in MOSFET

[kpsr]

Hello to all !

In MOSFET at strong inversion electrons confined to triangular quantum well, electrons occupy only 1 or 2 lowest subbands.
and the Van Dort model gives the quantum mechanical intrinsic carrier density in inversion channel via increased energy band-gap(ΔE).
N_QM = N_CL× Exp^(-ΔE/2kt) this carrier amount is very high.
But density of states for inversion charges in subbads reduced from the higher 3-D density to the lower 2-D density.

Then still HOW the above Van Dort's formula giving that high amount of charge..?

Thank You.

 

[eljose79]

Hello there,

Thank you for bringing up this interesting topic in MOSFETs and the Van Dort model. I would like to provide some insights and explanation to your question.

Firstly, let's understand the concept of strong inversion in MOSFETs. In strong inversion, the gate voltage is high enough to create a triangular quantum well in the channel region of the MOSFET. This well traps the electrons, making them confined to the lowest energy subbands. This is due to the potential energy barrier created by the gate voltage, which restricts the electrons to stay in the lower subbands.

Now, let's move on to the Van Dort model. This model takes into account the increased energy bandgap (ΔE) in the inversion region of the MOSFET. This increased energy bandgap is a result of the gate voltage, which creates a higher potential energy barrier for the electrons. This leads to a higher intrinsic carrier density (NQM) in the inversion channel, as shown in the formula you mentioned.

However, it is important to note that the density of states for inversion charges in the subbands is reduced from the higher 3-D density to the lower 2-D density. This means that the number of available energy states for the electrons is reduced, but the energy bandgap is still high. This results in a higher intrinsic carrier density in the inversion channel.

In conclusion, the Van Dort model takes into account the increased energy bandgap in the inversion region, which leads to a higher intrinsic carrier density. Even though the density of states is reduced in the subbands, the energy bandgap is still high, resulting in a high amount of charge according to the formula. I hope this helps clarify your question.

Thank you.