Metal–oxide–semiconductor structure, Electrical Engineering

Metal-Oxide-Semiconductor Structure

A traditional metal-oxide-semiconductor abbreviated as MOS structure is acquired by growing a layer of silicon dioxide (SiO2) on top of a silicon substrate and depositing a layer of metal or polycrystalline silicon (the latter is typically used). Since the silicon dioxide is a dielectric material, its structure is equal to a planar capacitor, along with one of the electrodes replaced by a semiconductor.

While a voltage is applied across a MOS structure, it changes the distribution of charges in the semiconductor. If we refer a P-type semiconductor (along with NA the density of acceptors, p the density of holes; p = NA in neutral bulk), a positive (+ive) voltage, VGB, from gate to body (see figure) forms a depletion layer by forcing the positively charged holes away from the gate-insulator or semiconductor interface, leaving exposed a carrier-free region of immobile, negatively charged acceptor ion. If VGB is sufficiently high, a high concentration of negative charge carriers forms in an inversion layer situated in a thin layer next to the interface in between the semiconductor and the insulator. Not like the MOSFET, in which the inversion layer electrons are supplied fast from the source or drain electrodes, in the MOS capacitor they are generated much more slowly by thermal generation by carrier generation and recombination centers in the depletion region.

145_Metal–oxide–semiconductor structure.png

                                      Figure: MOSFET structure and channel formation

Usually, the gate voltage at which the volume density of electrons in the inversion layer is similar as the volume density of holes in the body is called the threshold voltage. This structure along with p-type body is the basis of the N-type MOSFET that needs the addition of an N-type source and drain regions.

Posted Date: 1/11/2013 1:13:56 AM | Location : United States

Related Discussions:- Metal–oxide–semiconductor structure, Assignment Help, Ask Question on Metal–oxide–semiconductor structure, Get Answer, Expert's Help, Metal–oxide–semiconductor structure Discussions

Write discussion on Metal–oxide–semiconductor structure
Your posts are moderated
Related Questions
Q . Explain the working of Positive Clamper? Positive Clamper: The circuit for a positive clamper is shown in the figure. During the negative half cycle of the input signal,

Q. Consider a series-carry synchronous counter with T flip-flops shown in Figure in which the AND gates carry forward the transitions of the flip-flops, thereby improving the speed

Define and explain Numerical aperture? Figure shown below shows an incident ray to the fibre, The light bends at two interfaces, one at the air- core interface and the

Q. (a) In the circuit shown in Figure the zener diode (with zero zener resistance) operates in its reverse breakdown region while the voltage across it is held constant at VZ and t

Speed  Control of Three  Phase Induction Motors Three  phase  induction motors are invariably used in the application where in speed in  required to be  constant  or adjustabl

Q. A 20-kVA, 2200:220-V, 60-Hz, single-phase transformer has these parameters: Resistance of the 2200-V winding R1 = 2.50  Resistance of the 220-V winding R2 = 0.03  Lea

Q. How speech is transmitted in digital switching environment by using PCM/TDM? Ans: A digital carrier system is a communications system which uses digital pulses instead of

Explain Synchronisation and Parallel Operation Generation, transmission and distribution of electric power have to be conducted in an efficient and reliable way at a reasonable

UJT as relaxation oscillator: The UJT relaxation oscillator is shown in fig. it consist of a UJT and a capacitor C which is charged through a variable resistance R when VBB is