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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

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
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a perfect square v²+2v+_
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algebra 2 Inequalities:If equation 2 = 0 it is an open set?
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or infinite solutions?
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The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
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ramon Reply
Kristine 2*2*2=8
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Differences Between Laspeyres and Paasche Indices
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No. 7x -4y is simplified from 4x + (3y + 3x) -7y
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J, combine like terms 7x-4y
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Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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Cied
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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AMJAD
preparation of nanomaterial
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
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AMJAD
what is system testing
AMJAD
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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?
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Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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the Beer law works very well for dilute solutions but fails for very high concentrations. why?
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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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