Metal–oxide–semiconductor structure, Electrical Engineering

Assignment Help:

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.


Related Discussions:- Metal–oxide–semiconductor structure

Explain about zener diodes, Q. Explain about Zener Diodes? Most diodes ...

Q. Explain about Zener Diodes? Most diodes are not intended to be operated in the reverse breakdown region. Diodes designed expressly to operate in the breakdown region are cal

Complete instruction set of 8085 microprocessor , Complete Instruction Set ...

Complete Instruction Set of 8085 Microprocessor There are  total 256 instructions in  8085 microprocessor. These instructions are classified  into  seven categories  according

Laws of magnetic induction, The observations from these experiments led to ...

The observations from these experiments led to 'The Laws of Electromagnetic Induction' 1)  'If the magnetic flux threading through an electrical circuit changes, then an e.m.f.

Difference between write-through and write-back caches, The comparison can ...

The comparison can be made out of two feature 1) Performance and 2) Integrity of Data Write through is better in integrity as it will flush for every writes. Write b

Define electric current, Define Electric current If an electric pressur...

Define Electric current If an electric pressure or voltage is applied across any material there is a tendency for electrons to move in a certain direction. This movement of fre

How to reduce cost in embedded systems, Question: a) Give three ways h...

Question: a) Give three ways how to reduce cost in embedded systems. b) What is a microcontroller? How is it different to a microprocessor? c) Briefly comment on the "A

Pins and signals , Pins  and Signals As  discussed  earlier that  808...

Pins  and Signals As  discussed  earlier that  8085  microprocessor  chip has 40 pins shown  various  pins  and signals of 8085  microprocessor. All  these  signals can be   c

Define the time constant of the circuit, A coil of inductance 0.04 H and re...

A coil of inductance 0.04 H and resistance 10? is connected to a 120 V, d.c. supply. Verify (a)  The final value of current     (b)  The time constant of the circuit (c)

Threshold switching voltage, Analogue Threshold switching a) Include a...

Analogue Threshold switching a) Include a variable potential divider to the schematic diagram to control the transistor base voltage b) Include the potential divider compon

Ac-dc voltages , To do the basic laboratory experiments related to the elec...

To do the basic laboratory experiments related to the electrical engineering course, students need to have some basic understanding about the measuring tools, apparatus, components

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd