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In 1874, Braun noted the dependency of total resistance on the polarity of the applied voltage and on the surface conditions. By 1904, point contact diodes started coming into practical use. These were known as ‘Cat Whiskers’ used in crystal diode in demodulating the AM Radio Broadcast Signals. In 1931, Wilson gave the transport theory based on the Band Theory of Solids. In 1938, Schottky suggested that contact potential could develop at metal-semiconductor interface. The model based on this is known as Schottky Model. In 1938, Mott gave the model for swept-out Metal-Semiconductor contact. This is known as Mott barrier. In 1957, Henish in his book ‘Rectifying Semiconductor Contacts’ summarized the basic theory and the historical development of rectifying Metal-Semiconductor Contacts.

Table.3.4.1.Position of III and V elements energy states within the band-gap of Silicon.

The energy values refer to the energy below conduction bandedge in case of donor and refer to the energy above valence bandedge in case of acceptor .

[Reference: ‘Semiconductor Devices-basic principles’, by Jasprit Singh, Chapter 2,pp 74, 2007 reprint, Wiley –India Publication]

Semiconductor Impurity(Donor) E d (meV) Impurity(Acceptor) E a (meV)
Si Li 33 B 45
Sb 39 Al 67
P 45 Ga 72
As 54 In 100
Mn(deep EnergyStates) 530 Au(deep EnergyStates) 540
Zn(deep EnergyStates) 550

Deep energy states in the band-gap act as the effective stepping stone for recombination hence they act as the Life-Time killer. Their introduction will lead to reduction in minority carriers storage under forward bias condition.Hence in 70s to reduce the storage delay time, Gold was introduced as the life-time killer. But subsequently this was discarded and Schottky Clamped transistors were used to reduce the minority carrier storage delay. Nowadays Schottky-clamped TTL gates have become the norm of the day. These are available as 74AS series.

3.4.1. physics of schottky diode.

Aluminum layer on N-Type Semiconductor forms a rectifying junction with a built-in barrier potential as shown in Figure 3.27. and Figure 3.28.

In Figure 3.27. Case (a):

Work-function of Metal=qΦ m (eV).

Work-function of Siliconl=qΦ Si (eV).

Electron affinity in Silicon=χ Si (eV).

Barrier Potential Energy seen from metal side = qΦ B =q(Φ m Si ).

Barrier Potential seen from semi-conductor side =V bi = (Φ m Si ).

Built-in Barrier Potential on the semi-conductor side can be expressed as= V bi = (Φ B D ).

These are in ideal condition. In real – life, there are surface states at the interface which complicate the situation and measured values of Φ B are much greater than the theoretical values. Table 3.4.1. gives the measured Schottky Barrier heights for electrons on N-type Silicon Φ B N and the measured Schottky Barrier heights for holes on P-type Silicon Φ B P

Table 3.4.1. Measured Schottky Barrier heights for electrons on N-type Silicon Φ B N and the measured Schottky Barrier heights for holes on P-type Silicon Φ B P .

Metal Mg Ti Cr W Mo Pd Au Pt
Φ M (eV) 3.7 4.3 4.5 4.6 4.6 5.1 5.1 5.7
Φ B N (eV) 0.4 0.5 0.61 0.67 0.68 0.77 0.8 0.9
Φ B N (eV) - 0.61 0.50 - 0.42 - 0.3 -

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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