<< Chapter < Page Chapter >> Page >

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

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
Bharti
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
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Solid state physics and devices-the harbinger of third wave of civilization' conversation and receive update notifications?

Ask