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Here N C = effective density of states at E C (the lower edge of Conduction Band) ~10 19 /cc for all the three semiconductors namely Ge,Si and GaAs.

Here N V = effective density of states at E V (the upper edge of Valence Band) ~10 19 /cc for all the three semiconductors namely Ge,Si and GaAs.

E g = Band-Gap(eV), k = Boltzmann Constant, T = Absolute Temperature in Kelvin.

Table gives the intrinsic concentration of electrons and holes in Ge,Si and GaAs at Room Temperature (300K).

Table Intrinsic Concentration of electrons and holes in Ge,Si and GaAs at Temperature 300K.

Semiconductor Band-Gap Temperature Effective Density of States n i = p i
Ge 0.67eV 300K ~10 19 /cc 2.4×10 13 /cc
Si 1.12eV 300K ~10 19 /cc 4×10 9 /cc
GaAs 1.4eV 300K N C ~5×10 17 /cc, N V ~7×10 18 /cc 3.3×10 6 /cc

Figure 2.2.24 in the previous section illustrates how the EHP are thermally generated and why they are always equal.

Equation clearly shows that intrinsic concentration is very temperature sensitive.

Table. Concentration of Si from 300K to 360K

Temperature 300K 310K 320K 330K 340K 350K 360K
Intrinsic Conc(per cc) 4×10 9 8×10 9 1.5×10 10 2.8×10 10 5×10 10 9×10 10 1.45×10 11

From Table it is evident that for an increment of 60K above Room Temperature, intrinsic concentration has increased by two-orders of magnitude i.e. nearly 100 times. Because of this undesirable feature of intrinsic concentration, Si suffers from a very serious drawback namely: the reverse leakage current in a reverse biased diode doubles for every 10K rise in temperature.

In Figure 2.2.26, the exponential rise in intrinsic concentration with temperature is plotted.

2.2.5. Extrinsic Semi-conductor, space-charge neutrality and compensation .

Electronic Grade Semiconductor with no doping is called Intrinsic Semiconductor and that with doping is called Extrinsic Semiconductor.

Semiconductor is Group IV element or compound semi-conductor is Group (III+V) Compound.

For Group IV element, Group III(namely B, Al) is acceptor or P-Type dopent and Group V(P, As) is donor or N-Type dopent.

For Group (III+V)Compound semiconductor, Group II is acceptor or P-Type dopent and Group VI is donor or N-Type dopent.

In Figure 2.2.27, the consequence of introducing a donor atom or the consequence of introducing an acceptor atom in a Silicon Crystalline Lattice is shown.

In case of Donor doped Silicon where doping density is N D donor atoms/cc , the octave condition is completed by 4 valence electrons of donor atom hence 5 th valence electron beomes the odd-man out and hence is very loosely held by the host donor atom. At Room Temperature, the 5 th valence electron is broken loose from the donor and becomes a wanderer in Si-lattice. In effect Donor atom gets (+)ve ly ionized and donates its negatively charged 5 th valence electron to the Si-lattice.Hence overall space-charge neutrality is maintained. Plus there are thermally generated EHP also.Overall thermal equilibrium is achieved and we have thermal equilibrium concentration value(n n -bar) of conducting electron and thermal equilibrium value (p n -bar) of holes. Here conducting electrons are many orders of magnitude larger than holes hence electrons are referred to as majority carriers and holes are referred to as minority carriers.

Questions & Answers

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Damian Reply
absolutely yes
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Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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Mostly, they use nano carbon for electronics and for materials to be strengthened.
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s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
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for screen printed electrodes ?
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s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
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silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
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how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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