Amir Abdurahim EE4611 04112016 Introduction Is a FET Uses Heterojunction instead of PN junction Uses high mobility m aterials GaAs AlGaAs GaN AlGaN IIIV ID: 934083
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Slide1
High electron mobility transistors (HEMT)
Amir
Abdurahim
EE4611
04/11/2016
Slide2Introduction
Is a
FET
Uses Hetero-junction
instead of
PN
junction
Uses
high mobility
m
aterials (
GaAs
/
AlGaAs
,
GaN
/
AlGaN
, III-V)
Small gate-to-channel separation to keep capacitance and drift time to minimum
Slide3Introduction (continue)Optimum performance at 30– 300GHZ
Often used in high gain, low noise applications
Works best under high temperature (269c)
GaN
HEMT
works best for high power
applications due to its high band gap
InP
is super low noise transistor. Fastest transistor in the world (Cut off at 500GHZ)
Slide4Potential ApplicationsSatellite communication
Wireless communication
TV signals
Cellphones
Radars
radio astronomy
Slide5Before HEMT (GaAs MESFET)
GaAs
MESFET
Used in high frequency applications
GaAs
preferred due to its high carrier mobility
Si was replaced by
GaAs
Was used in application such as RF amplifiers
Slide6GaAs MESFET
GaAs
semiconducting layer has to be doped to ensure that the electrons are mobile
This
created a problem of
electrons
collision with impurities
The collision degraded the high mobility
of
GaAs
Slide7HEMTGaAs
/
AlGaAs
Hetero-
juction
: junction between two materials with 2 different band gap
forms a two
dimensional
electron gas (2-deg)
along the
GaAs
Conduction Channel along
GaAs
Slide8HEMT
Slide9HEMT (energy band interface)Electrons trapped in the quantum well due to band gap difference
It can accumulate up to 10^12/cm^2 in a thin layer of <900nm
No depletion since
AlGaAs
is fully depleted under normal condition
Slide10HEMT (energy band interface)Creation of quantum well
Slide11Summary and ConclusionHEMT uses Hetero-junction instead of PN junction Used in high bandwidth, low noise and high power applications
Small
gate-to-channel separation to keep capacitance and drift time to minimum
Electrons accumulate in the conduction channel as 2 dimensional
electron gas (
2-DEG)
HEMT has the ability to locate a
large electron density in a thin layer
(<900nm)
High
electron mobility
and
maximum electron
velocity in
GaAs
makes
more applicable than MESFET
Slide12Work citedPal, Gyan Prakash, and Anuj
Kumar
Shrivastav
. "International Journal of Scientific and Engineering Research."
International Journal of Scientific Research Engineering &Technology (IJSRET)
(2012): 43+. Web. 08 Apr. 2016
.
Poole, Ian. "HEMT, High Electron Mobility Transistor Tutorial."
What Is a HEMT. Adrio
Communications Ltd. Web. 08 Apr. 2016
.
Poole, Ian. "
GaAs
FET MESFET Tutorial."
MESFET /
GaAs
FET| MEtal
Semiconductor FET / Gallium Arsenide
.
Adrio
Communications Ltd. Web. 08 Apr. 2016
.
Zhaojun
Liu,
Tongde
Huang,
Qiang
Li, Xing Lu, and
Xinbo
Zou
Synthesis
Lectures on Emerging Engineering Technologies 2016 2:3, 1-73
Slide13Five conceptsHEMT is a Field transistorHEMT uses Hetero-junction rather than PN junction
Small gate-to-channel separation to keep capacitance and drift time to
minimum
HEMT used for high gain and low noise applications
Works best under high temperature