Question

How is the metallurgical channel thickness between the gate and the substrate related to the doping concentration of the channel?

(a) Inversely proportional to the square root of the doping concentration

(b) Logarithmically related to the square root of the doping concentration

(c) Directly proportional to the square root of the doping concentration

(d) Exponentially related to the square root of the doping concentration

This question was addressed to me in an interview.

I'm obligated to ask this question of Characteristics of JFET topic in chapter FET Amplifiers of Analog Circuits

Answer 1

The correct answer is (a) Inversely proportional to the square root of the doping concentration

The best explanation: The channel thickness is inversely related to the square root of the doping concentration of the channel. This is because the electric field developed is proportional to the channel doping concentration while the relation between the potential, electric field and doping concentration is visible from the Poisson’s equation.