If gate is directly in contact with dielectric material (insulator), how can we define the work function of gate. Please assist me with this.
Dear friend Nudrat Sufiyan
The work function of a gate refers to the amount of energy required to remove an electron from the gate material and move it to the vacuum level. In a MOSFET (metal-oxide-semiconductor field-effect transistor), the gate is typically made of a conductive material, such as doped polysilicon, metal or metal alloy.
When the gate is in direct contact with the dielectric material, the work function of the gate can be determined by measuring the energy difference between the Fermi level of the gate material and the vacuum level. The Fermi level is the energy level at which there is a 50% probability of finding an electron in a material at absolute zero temperature.
In practical terms, the work function of the gate is typically determined by measuring the threshold voltage of the MOSFET. The threshold voltage is the gate voltage at which the transistor just starts to conduct. By measuring the threshold voltage and knowing the properties of the dielectric material, the work function of the gate can be calculated using the following equation:
work function of gate = threshold voltage - (dielectric constant x electron charge x channel doping concentration)/(gate capacitance x oxide thickness)
In this equation, the dielectric constant, electron charge, channel doping concentration, gate capacitance, and oxide thickness are all known quantities that can be measured or determined based on the design and fabrication of the MOSFET.
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