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Since CVPD is carried out at 1270ºC, there is the problem of out-diffusion of Arsenic from the substrate into the epitaxial layer. Arsenic is used as buried layer to reduce the series collector resistance of Vertical NPN transistor. Arsenic has very low diffusion coefficient still at the elevated temperature of 1270ºC, some out-diffusion is inevitable. To prevent this out-diffusion altogether, we use Liquid Phase Epitaxy which is shown in Figure 12.


The Liquid Phase Epitaxy set up is shown in Figure 12.This is carried out at 900ºC hence the problem of out-diffusion is completely prevented but Silane which is used for LPE is highly toxic. As seen in Figure 12, there is a super saturated solution of Silane kept at 900ºC. By Graphite Slider, the silicon substrate is brought directly underneath the well containing Silane. As Substrate comes in contact with Silane , latter is dissociated into Silicon and Hydrogen and Silicon precipitates onto the substrate forming an epitaxial film on the substrate.


Due to explosive demand of Wireless Communication Equipment there has been a sudden spurt in demand of MBE equipments particularly of multiple wafer MBE equipment which can give a high throughput of epitaxilly prepared wafers.

There are two kinds of epitaxial film growth: Homoepitaxy (same composition) and Heteroepitaxy (different composition). By Molecular Beam Epitaxy, multi-layered thin films of single crystals of different compositions and of atomic dimension can be grown. In effect we can achieve heteroepitaxy which is the hallmark of compound semiconductor devices such as Photonic Devices and GaAs MESFET.

MBE is a process for making compound semiconductor materials with great precision and purity. These materials are layered one on top of the other to form semiconductor devices such as transistors and lasers. These devices are used in such applications as fiber-optics, cellular phones, satellites, radar systems, and display devices. MBE is used for fabrication of Super-lattices and hetero-junction MESFET. Super lattices are periodic structures of alternating Ultra-thin layers of compound semiconductor.

MBE growth produces complex structures of varying layers which are further processed to produce a range of electronic and optoelectronic devices, including high speed transistors, light-emitting diodes, and solid state lasers. MBE is a powerful technique both for research into new materials and layer structures, and for producing high-performance devices.

Referring to Figure 13:

The walls of the chamber cooled with liquid nitrogen. This cryogenic screening around the substrate minimizes the spurious flux of contaminating atoms and

Sample Exchange Load Lock-this permits maintenance of Ultra High Vacuum while changing the substrate.

Effusion Cells- this contains the solid source to be evaporated and deposited on the substrate. Temperature of the effusion oven is adjusted to give desired evaporation rate.

Rotating Substrate Holder- rotation of substrate ensures less than ±1% doping variation and ±0.5% in thickness variation.

Questions & Answers

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
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
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
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
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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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