Customer Service Chat
Get quote & make Payment
Electrons and holes, Electrical Engineering
ons and Holes
For T> 0 K, there would be some electrons in the otherwise empty conduction band, and some empty states in the otherwise filled valence band.
The empty states in the valence band are referred to as holes.
If the conduction band electron and the valence band hole are created by thermal excitation of a valence band electron to the conduction band, then they are called electron-hole pair (EHP).
After excitation to the conduction band, an electron is surrounded via a large number of empty states, for example the equilibrium number of EHPs at 300 K in Si is ∼10
, whereas the Si atom density is ∼10
Thus, the electrons in the conduction band are free to move about via the many available empty states.
Corresponding problem of charge transport in the valence band is slightly more complex.
Current transport in the valence band can be accounted for by keeping track of the holes themselves.
In a filled band, all available energy states are occupied.
For every electron moving with a given velocity, there is an equal and opposite electron motion somewhere else in the band.
Under an applied electric field, the net current is zero, since for every electron j moving with a velocity V
, there is a corresponding electron j moving with a velocity - V
In a unit volume, the current density J can be given by
(filled band) (2)
where N is the number of electrons/cm
in the band, and q is the electronic charge.
Now, if the j
electron is removed and a hole is created in the valence band, after that the net current density
Thus, the current contribution of the empty state (hole), obtained by removing the jth electron, is equivalent to that of a positively charged particle with velocity V
Note that actually this transport is accounted for by the motion of the uncompensated electron j having a charge of q and moving with a velocity V
Its current contribution (-q) (-V
) is equivalent to that of a positively charged particle with velocity + V
For simplicity, therefore, the empty states in the valence band are called holes, and they are assigned positive charge and positive mass.
The electron energy increases as one move up the conduction band, and electrons gravitate downward towards the bottom of the conduction band.
On the other hand, hole energy increases as one moves down the valence band (since holes have positive charges), and holes gravitate upwards towards the top of the valence band.
Posted Date: 1/11/2013 4:30:30 AM | Location : United States
Ask an Expert
Electrons and holes, Assignment Help, Ask Question on Electrons and holes, Get Answer, Expert's Help, Electrons and holes Discussions
Write discussion on Electrons and holes
Your posts are moderated
Write your message here..
Dc electric motors, T h er e are three main types - The Shu...
T h er e are three main types - The Shunt Connected DC motor in which the armature coils are connected in parallel with the field coils The Serie
Give examples of natural insulating materials, Give four examples of natura...
Give four examples of natural insulating materials. Illustrations of the natural insulating materials are rubber, cotton, wood and mica.
Draw an electrical relay diagram, Draw an electrical relay diagram rung sho...
Draw an electrical relay diagram rung showing a N/O contact of CR1(coil) in series witha N/C contact of CR2(Coil), operating a lamp L1. A delay-on (TON) relay has a preset of 5.
Show output characteristic of common emitter configuration, Q. Show output ...
Q. Show output Characteristic Of Common Emitter Configuration? Output characteristics: This family of curves may be divided into three regions just as was done for common base
Determine transformer turns ratio, A flyback converter is to be designed so...
A flyback converter is to be designed so that it operates in continuous "current" (flux) mode with a duty cycle of D = 0.45 when input voltage V s = 48 V, output voltage V o = 30
Explain sahf instructions in 8086 family, Explain SAHF instructions in 80...
Explain SAHF instructions in 8086 family with example and their effect on flag. SAHF: Store AH register in flag register, this is an instruction utilized to store the data i
Find the duration t of the pulse, By a simple time multiplexing of natural ...
By a simple time multiplexing of natural samples over a single line, a large radar site transmits 85 analog signals, each with 200-Hz bandwidth. If the sampling is done at twice th
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
Explain shunt-field control process, Q. Explain Shunt-field control process...
Q. Explain Shunt-field control process? Shunt-field control, armature-resistance control offers a constant-torque drive because both flux and, to a first approximation, allowab
Determine the output resistance of the circuit, Q. (a) Consider the ampl...
Q. (a) Consider the amplifier block in the circuit configuration of Figure. Find an expression for v 2 /v 1 in terms of R i , R o , and A of the amplifier. (b) Determine the
Accounting Assignment Help
Economics Assignment Help
Finance Assignment Help
Statistics Assignment Help
Physics Assignment Help
Chemistry Assignment Help
Math Assignment Help
Biology Assignment Help
English Assignment Help
Management Assignment Help
Engineering Assignment Help
Programming Assignment Help
Computer Science Assignment Help
Why Us ?
~24x7 hrs Support
~Quality of Work
~Time on Delivery
~Privacy of Work
Human Resource Management
Literature Review Writing Help
Follow Us |
T & C
Copyright by ExpertsMind IT Educational Pvt. Ltd.