Graphene has potential applications in future semiconductor devices due to its unique electrical and thermal properties. It has minimum electrical resistance and high thermal conductivity, making it a promising semiconductor material. Graphene is produced through exfoliation, chemical vapor deposition, and other methods. Its application in radio frequency transistors could allow for fast switching speeds and high "on" currents. Graphene may help overcome limitations of traditional semiconductors like silicon in dissipating heat from densely-packed devices.

1. GRAPHENE
FUTURE OF SEMICONDUCTOR DEVICES
MONIKUNTALA BHATTACHARYA
ROLLNO:001730701021
DEPARTMENT OF NANO SCIENCE
AND TECHNOLOGY
JADAVPUR UNIVERSITY
1Monikuntal Bhattacharya

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 Semiconductor:
Semiconductor=Semi+conductor
A semiconductor material has an electrical conductivity value falling between that of a conductor, such as copper,
and an insulator, such as glass.
Electrical Conductivity: Electrical conductivity is the measure of a material's ability to allow the transport of
an electric charge. Its SI is the siemens per meter (named after Werner von Siemens), Sm−1. It is the ratio of the
current density to the electric field strength.
 Semiconductor materials:
1. Silicon
2. Germanium
3. Gray tin
4. Silicon Carbide
5. Grey Selenium, Tellurium
 Difference of semiconductor from a conductor and importance of semiconductor:

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 Basic working principle of semiconductor
Monikuntal Bhattacharya
PURE
SILICON/GERMANIUM
IMPURITIES DOPED
SEMICONDUCTOR
IMPURITIES
P-TYPE
ex: boron and gallium
N-TYPE
ex :phosphorus and
arsenic

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A 1 cm3 specimen of a metal or semiconductor has of the order of 1022 atoms. In a metal, every atom donates at
least one free electron for conduction, thus 1 cm3 of metal contains on the order of 1022 free electrons, whereas a
1 cm3 sample of pure germanium at 20 °C contains about 4.2×1022 atoms, but only 2.5×1013 free electrons
and 2.5×1013 holes. The addition of 0.001% of arsenic (an impurity) donates an extra 1017 free electrons in the same
volume and the electrical conductivity is increased by a factor of 10,000.

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 PN JUNCTION DIODE

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 Drawbacks of semiconductors:
Semiconductor shows certain disadvantages which doesn’t make it suitable very sophisticated applications.
One major drawback of semiconductor is that they heat up quickly and cannot dissipate the heat. This is a
major problem because it could lead to the meltdown of the entire computer chip. So it becomes very
important to find some other material which can dissipate heat faster.
 Introduction to GRAPHENE era:
 named by Hanns-Peter Boehm, who described single-layer carbon foils in 1962
 The term graphene first appeared in 1987 to describe single sheets of graphite.
 Ultimate two-dimensional, atomic-scale, hexagonal lattice in which one atom forms each vertex

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 Properties of Graphene:
1. Minimum resistance to electron making it a great semiconductor
2. Great thermal conductivity; heat can move ten times faster through graphene.
 Structure of graphene:

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 Graphene production method:

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There are different methods of Graphene production , namely
1. Exfoliation
2. Reduction
3. Electrochemical synthesis
4. Tang-Lau Method
5. Chemical Vapor Deposition (CVD) Method

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• Exfoliation
• US 8747623 B2
• Inventors:Aruna Zhamu, Bor Z. Jang
Liquid
Intercalating
agent
Suspension
Exfoliated
Graphite or
Graphene
Microwave for
30sec-5min
• Liquid Intercalating Agent:: Dilute acids or weaker acids, such as acetic acid and formic acid.
• Microwave Frequency: 2 and 10 GHz (Domestic Microwave 2.45GHz)
Graphite
powder

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• Chemical Vapor Deposition (CVD) Method
• Ni film is cooled from 900°C to 725°C

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 Futuristic Application:
• Radio Frequency(RF) Transistor
P-N-P Configuration

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• Semiconductor device which is used in order to amplify and switch electronic signals and power
• Three terminals for connection.
• A transistor can use a small signal applied between one pair of its terminals in order to control a much larger
signal at another pair of terminals. This is called gain.
• Working frequency: low frequency (up to 5GHz) and medium frequency applications (up to 14GHz) (Infineon
RF transistors)
• Radio-frequency transistor performance is characterized by two parameters: the cutoff frequency (fT)
(the frequency at which the current gain is unity) and the maximum oscillation frequency (fmax)
(the frequency at which the power gain is unity).
• Mathematically,
𝑓 𝑇=
𝑔 𝑚
2𝜋𝐶 𝐺
Where CG represents gate capacitance, gD is the channel conductance, RG is the gate resistance and RSD is the
source–drain resistance
𝑓
𝑚𝑎𝑥 =
𝑓 𝑇
2 𝑔 𝐷 𝑅 𝐺+𝑅 𝑆𝐷 +2𝜋𝑓 𝑇 𝑅 𝐺 𝐶 𝐺

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Application of Graphene in RF Transistor
• Obtaining fast switching and a high ‘on’ current
• Zero bandgap induces a large ‘off’ current, results in on/off current ratios for graphene transistors are about
100, much lower than the required for mainstream logic applications.
• Highest measured fT has been 300 GHz with Co2Si-nanowire gates using exfoliated graphene.
• Low output resistance is one of the key factors in increasing fmax. Because fmax measures transmitted
power), it can be increased by minimizing gD attained at channel saturation.

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 References:
• Tudor Jenkins, “A brief history of ... semiconductors” , IOPScience, Vol-40,No-5
• Gianluca Fiori, Francesco Bonaccorso, Giuseppe Iannaccone, Tomás Palacios, Daniel Neumaier, Alan Seabaugh, Sanjay
K. Banerjee & Luigi Colombo, “Electronics based on two-dimensional materials”, Nature Nanotechnology, 9, P: 768–779
(2014)
• Kinam Kim, Jae-Young Choi, Taek Kim, Seong-Ho Cho & Hyun-Jong Chung, “A role for graphene in silicon-based
semiconductor devices”, Nature 479,P: 338–344 (17 November 2011)
• Brian Standley, Wenzhong Bao, Hang Zhang, Jehoshua Bruck,Chun Ning Lau and Marc Bockrath, “Graphene-Based
Atomic-Scale Switches”, Nano Letters,2008,Vol. 8, No. 10, P: 3345-3349
• Dr. Angela Hullmann,” The economic development of nanotechnology - An indicators based analysis”, European
Commission, DG Research, Unit “Nano S&T - Convergent Science and Technologies”
• AasgeirHelland & HansKastenholz, “Development of nanotechnology in light of sustainability”, Journal of Cleaner
Production,Volume 16, Issues 8–9, May–June 2008, P:885-888
• Norman Dye &Helge Granberg, “Radio Frequency Transistors, Principles and Practical Applications”, Second Edition,
Newnes
• https://en.wikipedia.org
• http://www.futureelectronics.com/en/wireless-rf-radio-frequency/rf-transistors.aspx
• https://www.google.co.in

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