If fixed positive charges are present in the gate oxide of an n-c
| If fixed positive charges are present in the gate oxide of an n-channel enhancement type MOSFET it will lead to
A. a decrease is the threshold voltage
B. channel length modulation
C. an increase in substrate leakage current.
D. an increase in accumulation capacitance.
Please scroll down to see the correct answer and solution guide.
Right Answer is: A
SOLUTION
Definition:
Concept:
Threshold voltage: It is the minimum gate to source voltage required at which the channel formation takes place and a low resistance conducting path between source and drain is formed.
Consider the n-MOS shown below:
- If we apply a potential source between the drain and the source, no current will flow as there is no conducting path between the drain and the source.
- To provide the conducting path between the drain and the source, we apply a positive potential at the gate.
- On applying positive potential, there is an induced electric field at the semiconductor surface below the oxide, trapping the electrons (minority carrier of the p-type substrate). This results in the formation of a conducting path channel between the drain and the source.
- The channel created is also called as the Inversion layer, and the threshold voltage is the voltage required to form this inversion layer.
- Now, when we already a fixed positive charge is present in the gate oxide, lesser voltage will be required at the gate for the formation of channel, which is nothing but the threshold voltage.
∴ The threshold voltage will decrease if there is already an oxide charge stored.
