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Under no bias, there is equal current flowing across the potential barrier from two sides. Hence there is detailed charge balance is maintained and net current across the Schottky Barrier is zero.

The Barrier Potential seen from the metal side is Φ B and remains unchanged even under bias condition. Hence current from Metal to Semiconductor is kept at -I 0 under forward as well as reverse biased condition..

But the Barrier Potential from the semiconductor side is (V bi -V F ) under forward bias condition just as in Classical Diode and as shown in Figure 3.29. Hence carrier diffuses across the forward biased junction with a greater ease and the current from Semiconductor to Metal is I 0 Exp[V F /V Th ]. Therefore net current across the junction under forward bias condition is:

Under reverse bias condition, the barrier potential from Metal-side is unchanged but from the Semiconductor-side it is (V bi +V F ) as shown in Figure 3.30. Hence electron diffusion across the enhanced potential barrier is completely stopped and net current across the junction is:

Equation 3.4.1 and Equation 3.4.2 show that Schotky diode behaves exactly like a classical Diode except for a lower knee Voltage at 0.1V because of a reduced barrier potential.

Detailed analysis of Schittky Diode will be done in Supplementary Sheets.

3.4.2. data-sheet of schottky diode.

As shown in Section 3.4.1, there is no minority carrier involved in the diode action. It is electron bothways. Hence there is no minority carrier storage and hence as we will see in the switching transients we are never confronted with mionority carrier storage delay in switching transients. Therefore Schottky Diode is known as ‘Hot-Electron Diode’.

It has a lower cut-in voltage of 0.1V because of lower barrier potential. And it has much lower junction plus diffusion capacitance. In Table 3.4.2.1. comparative data sheets of a Schottky Diode 1N5711 and Classical Diode 1N4001 are given.

Low fotward voltage drop and fast switching makes it ideal for protection of MOS devices, steering, biasing and coupling diodes for fast switching and low logic level application. It has higher cut-off frequency, it is reproducible and it has ease of fabrication.

In Figure 3.31, its symbol and I-V characteristics in comparison to I-V characteristics of a classical diode is shown.

Table 3.4.2.1. Comparative Data Sheets of Schottky Diode 1N5711 and Classical Diode 1N4001.

1N5711(Schottky Diode) 1N4001(Classical Diode)
PIV 70V PIV 50V
P D 400mW P D 500mW
I D0 200nAAt V R =-50V I D0 5μAAt V R =-50V
V γ 0.1V At 10μA V γ 0.5V At 10μA
V F 0.4V At 1mA V F 0.65V At 1mA
C Tot 2pF 20pF
t rr (ReverseRecovery time) 1ns 3μs

3.4.3. application of schottky diode in ttl gates.

TTL Gate (Transistor-Transistor Logic)74Series is the most commonly used Saturating Logic Family. It suffered from a serious drawback and that was of SPEED. TTL under HIGH conditiont is in cut-off region and in LOW condition it is in deep-saturation. While switching from LOW to HIGH, it suffered from considerable storage delay because of deep-saturation and because of excessive minority carrier storage in the BASE in saturation mode. But if we put a Schottky Diode in parallel to BC Juncttion then even before BC junction is fully forward biased Schottky Diode is turned on.This prevents the BJT from going into deep saturation. A Schottky Clamped Transistor as shown in Fig 3.32. is barely saturated when it goes to LOW condition. Therefore it quickly comes out of Saturation Region and moves to Cut-Off region.This considerably improves the switching speed and toggle rate. The cross-section and the symbol of a Schottky Clamped Transistor used in TTL gate is shown in Figure 3.32. Such a TTL gate is known as Schottky Clamped TTL in 74AS series.

3.5. Ohmic Contact.

Aluminum contact pad to P-Type semiconductor is an ohmic contact but Aluminum contact pad to N-Type semiconductor is a rectifying contact which we have seen to be Schottky Diode as seen in Figure 3.32. In Si-ICs, ohmic contact to N-Type Collector is never made directly. First a N+ contact region is diffused in N Collector and then Al contact pad is deposited on N+ contact region as shown in Figure 3.33.

In nanotechnology era, greater care is taken in making contact with N-semiconductor as show in Figure 3.34.

As seen in Figure 3.34. upper layer of heavily doped N+ region is converted into Titanium Silicide. Over this Silicide layer, Oxide layer is deposited. A contact hole is made in Oxide Layer to reach Titanium Silicide. A thin layer of Titamium Nitride is deposited lining the contact hole. This prevents the reaction and inter-diffusion between Silicide and Tungsten Plug.Tungsten Plug is deposited by CVD to fill the contact hole. Over the Tungsten Plug a layer of Metal(Al with some minute quantity of Cu) is deposited to make contact with the underlying N+ region via the tungsten Plug. This gives an ideal ohmic contact.

Questions & Answers

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
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it is a goid question and i want to know the answer as well
Maciej
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Abigail
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 ?
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
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
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Cied
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Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
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Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
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what is nanomaterials​ and their applications of sensors.
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what is nano technology
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what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
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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