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(High Electron Mobility Transistor)
A REVOLUTION FOR HIGH SPEED DEVICES
•SCHOOL OF MATERIAL SCIENCE
AND
NANOTECHNOLOGY
•BRIEF HISTORY
•LIMITATIONS OF CONVENTIONAL
TRANSISTORS
•HEMT INTRODUCTION
•HETEROJUNCTION REQUIREMENT
•BAND STRUCTURE AND...
• 1960 GaN small crystals was made.
• 1980 Takashi Mimura, Fujitsu laboratories
designed the features of the first HEMT.
•...
•Short channel effects
•Gate leakage current
•Gate power dissipation
•Ionizing Impurities
•Lattice and impurities scatteri...
HIGH ELECTRON MOBILITY TRANSISTORS (HEMT)
•High speed device
•Referred to as heterojunction field effect transistors.
•Two...
•Two disimmilar semiconductor having
different band energies.
•Lattice match between them.
Alx Ga(1-x)As/GaAs have excelle...
= 1.798 eV= 1.424 eVEg1
EC1
EF1
EV1
EC2
EF2
EV2
Eg2
p-type GaAs
Heavily doped
n-type Al0.3Ga0.7As
Moderately doped
Eg1
EC1
Evac
qfm1
EF1
EV1
qc1
Evac
qfm2qc2
EC2
EF2
EV2
Eg2
Electron affinities qc1 for GaAs and qc2 AlxGa1-xAs
Eg1
EC1
Evac
qfm1
EF1
EV1
qc1
Results so far: EC1 and EC2 band-bending:
J
AlGaASaGaAs
Evac
qfm2qc2
EC2
EF2
EV2
Eg2
Eg1
EC1
Evac
qfm1
EF1
EV1
qc1
Keeping the electron affinities correct resulted in a triangula...
We have got electron which
have got a high mobility, put a
contact between two ends.
If we apply a vltage between
them the...
Originally for high speed applications
•High power/ high temperature microwave
applications
•Power amplifiers
•Oscillators...
• Fantastic mobility. 2,50,000cm2/Vsec at 77K and
20,00,000cm2/Vsec at 4K. APROX 200-300 times more than
conentional trans...
ppt Hemt(high electron mobility transistor)
ppt Hemt(high electron mobility transistor)
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ppt Hemt(high electron mobility transistor)

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high electron mobility transistor

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ppt Hemt(high electron mobility transistor)

  1. 1. (High Electron Mobility Transistor) A REVOLUTION FOR HIGH SPEED DEVICES •SCHOOL OF MATERIAL SCIENCE AND NANOTECHNOLOGY
  2. 2. •BRIEF HISTORY •LIMITATIONS OF CONVENTIONAL TRANSISTORS •HEMT INTRODUCTION •HETEROJUNCTION REQUIREMENT •BAND STRUCTURE AND BAND BENDING •HOW THEY WORK?? •SWITCHING IN HEMT •APPLICATIONS •CONCLUSIONS •REFERENCES
  3. 3. • 1960 GaN small crystals was made. • 1980 Takashi Mimura, Fujitsu laboratories designed the features of the first HEMT. • 1985 HEMT was announced the lowest noise device. • 1994 the first AlGaN/GaN HEMT was demonstrated . • After 2010 it is widely used for high speed devices.
  4. 4. •Short channel effects •Gate leakage current •Gate power dissipation •Ionizing Impurities •Lattice and impurities scattering •Less mobility •Less transconductance
  5. 5. HIGH ELECTRON MOBILITY TRANSISTORS (HEMT) •High speed device •Referred to as heterojunction field effect transistors. •Two layer of different semiconductor with different band gap energies. 2-D ELECTRON GAS LESS ELECRON COLLISION LESS NOISE+HIGH MOBILITY
  6. 6. •Two disimmilar semiconductor having different band energies. •Lattice match between them. Alx Ga(1-x)As/GaAs have excellent match.
  7. 7. = 1.798 eV= 1.424 eVEg1 EC1 EF1 EV1 EC2 EF2 EV2 Eg2 p-type GaAs Heavily doped n-type Al0.3Ga0.7As Moderately doped
  8. 8. Eg1 EC1 Evac qfm1 EF1 EV1 qc1 Evac qfm2qc2 EC2 EF2 EV2 Eg2 Electron affinities qc1 for GaAs and qc2 AlxGa1-xAs
  9. 9. Eg1 EC1 Evac qfm1 EF1 EV1 qc1 Results so far: EC1 and EC2 band-bending: J AlGaASaGaAs
  10. 10. Evac qfm2qc2 EC2 EF2 EV2 Eg2 Eg1 EC1 Evac qfm1 EF1 EV1 qc1 Keeping the electron affinities correct resulted in a triangular quantum well in EC (for this heterojunction combination): J In this region: a triangular quantum well has developed in the conduct DEC GaAs AlGaAs
  11. 11. We have got electron which have got a high mobility, put a contact between two ends. If we apply a vltage between them the electron gets tansported. Electrons locked up here can be used up by tranporting them. ee ee e
  12. 12. Originally for high speed applications •High power/ high temperature microwave applications •Power amplifiers •Oscillators •Cell Phones •Radar •Most MMIC’s radio frequency •Comaptible for nano devices
  13. 13. • Fantastic mobility. 2,50,000cm2/Vsec at 77K and 20,00,000cm2/Vsec at 4K. APROX 200-300 times more than conentional transistors. •Its two main features are low noise and high frequency capability. •A heterojunction is two layers different semiconductors with different band gap energies. •The 2-D electron gas is essential to the low noise feature. •AlGaAs and GaAs are the most common materials for heterojunction.

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