Extrinsic material, Electrical Engineering

Assignment Help:

Extrinsic Material

  • In addition to thermally generated carriers, it is possible to create carriers in the semiconductor by purposely introducing impurities into the crystal => doping.
  • Most common technique for varying the conductivity of semiconductors.
  • By doping, the crystal can be made to have predominantly electrons (n-type) or holes (p- type).
  • When a crystal is doped such that the equilibrium concentrations of electrons (n0) and holes (p0) are different from the intrinsic carrier concentration (ni), the material is said to be extrinsic.
  • Doping creates additional levels within the band gap.
  • In Si, column V elements of the periodic table (e.g., P, As, Sb) introduce energy levels very near (commonly 0.03-0.06 eV) the conduction band.
  • At 0 K, these levels are filled with electrons, and very little thermal energy (50 K to 100 K) is required for these electrons to get excited to the conduction band.
  • Since these levels donate electrons to the conduction band, they are referred to as the donor levels.
  • Thus, Si doped with donor impurities can have a significant number of electrons in the conduction band even when the temperature is not sufficiently high enough for the intrinsic carriers to dominate, i.e., n0>> ni, p0 => n-type material, with electrons as majority carriers and holes as minority carriers.
  • In Si, column III elements of the periodic table (for example, B, Al, Ga, In) introduce energy levels very near (commonly 0.03-0.06 eV) the valence band.
  • At 0 K, these levels are empty, and very little thermal energy (50 K to 100 K) is required for electrons in the valence band to get excited to these levels, and leave behind holes in the valence band.
  • Since these levels accept electrons from the valence band, they are referred to as the acceptor levels.
  • Thus, Si doped with acceptor impurities can have a significant number of holes in the valence band even at a very low temperature, i.e., p0>> ni, n0 =>, p-type material, along with holes as majority carriers and electrons as minority carriers.
  • The extra electron for column V elements is loosely bound and it can be liberated very Easily => ionization; thus, it is free to participate in current conduction.
  • Similarly, column III elements create holes in the valence band, and they can also participate in current conduction.
  • Rough calculation of the ionization energy can be made based on the Bohr's model for H2 atoms, considering the loosely bound electron orbiting around the tightly bound core electrons. Thus,

    1536_Extrinsic Material.png

Where εr is the relative permittivity of Si.


Related Discussions:- Extrinsic material

Determine the equivalent capacitance, Q. Determine the equivalent capacitan...

Q. Determine the equivalent capacitance at terminals A-B for the circuit configurations shown in Figure.

Explain the working of a photo - transistor with a sketch, Q. Explain the w...

Q. Explain the working of a photo - transistor with a sketch A second optoelectronic device that conducts current when exposed to light is the PHOTOTRANSISTOR. A phototransisto

High voltage distribution system or hvds, High Voltage Distribution System ...

High Voltage Distribution System or HVDS Adoption of HVDS (High Voltage Distribution System) through converting existing LVDS to HVDS reduces the technical losses appreciably.

Kpi for second stage implementation, KPI for Second Stage Implementation ...

KPI for Second Stage Implementation These KPIs deal along with the quality of the relationship among a supplier and a user (customer). They are significant to potential custom

Mention the three transistor configurations, Q. Mention The Three Transisto...

Q. Mention The Three Transistor Configurations? The three transistor configurations are 1)Common emitter configuration 2)Common base configuration 3)Common collector c

What do you mean by nibble, Q. What do you mean by Nibble? The nibble i...

Q. What do you mean by Nibble? The nibble is a collection of bits on a 4-bit boundary. It would not be a particularly interesting data structure except for two items BCD (binar

Formal lab report, I need someone help me to do electronics formal lab repo...

I need someone help me to do electronics formal lab report, I tried many time to submit it but I couldn''t? plz help me

Show how emitter amplifier work as a buffer amplifier, Q. Due to what speci...

Q. Due to what special property does an emitter amplifier work as a buffer amplifier?  The circuit design of the emitter follower is such that it has a high input impedance and

Determine the electric force on each charge, Q. Point charges, each of √4πε...

Q. Point charges, each of √4πε 0 C, are located at the vertices of an equilateral triangle of side a. Determine the electric force on each charge.

Define spectrum of real signals, Define Spectrum of Real Signals? In th...

Define Spectrum of Real Signals? In the real world, we rarely come throughout a pure sine wave. Typical signals have a wide spectrum as displayed in the above diagram. Informat

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