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High Electron Mobility Transistor (HEMT)
Flament Benjamin
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PLAN Presentation Fabrication
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Presentation 1980 at Fujitsu TEGFET, MODFET, HFET
Goal->transportation in a doped material
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Presentation Heterojunction: 2 layers
Highly doped layer with grand gap Non-doped layer with small gap
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Energy band diagram
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Transfert des charges Source Gate Drain CAP small doped gap
CAP small doped gap Schottky contact grand gap non doped Carrier donor layer grand gap doped Spacer grand gap non doped Canal small gap non doped Buffer grand gap non doped Substrat Transfert des charges
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PLAN Presentation Fabrication
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Plan Cleaning Deposition, MBE Ohmic contacts
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Fabrication Cleaning of the wafer
GaAs wafer->more complicated than Si wafer Difficulties to remove the oxide of Ga and As We use the electron cyclotron resonance (ECR)
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Fabrication As oxide is removed by heating and :
x=1, 3, 5 stands for the various oxides of arsenic Ga oxide is removed by:
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Fabrication Becomes volatile at 200°C so we choose a
temperature of 400°C
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Fabrication We grow the different layer by molecular beam epitaxy (MBE)
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30 periods of AlGaAs/GaAs superlattice buffer
Buffer grand gap non doped Substrat 30 periods of AlGaAs/GaAs superlattice buffer 30 periods of AlGaAs/GaAs superlattice buffer
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120 Å of In(0.2)Ga(0.8)As Canal small gap non doped
Buffer grand gap non doped Substrat 120 Å of In(0.2)Ga(0.8)As
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35 Å of Al(0.23)Ga(0.77)As Spacer grand gap non doped
Canal small gap non doped Buffer grand gap non doped Substrat 35 Å of Al(0.23)Ga(0.77)As
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Carrier donor layer grand gap doped
Spacer grand gap non doped Canal small gap non doped Buffer grand gap non doped Substrat
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250 Å of Al(0.23)Ga(0.77)As Schottky contact grand gap non doped
Carrier donor layer grand gap doped Spacer grand gap non doped Canal small gap non doped Buffer grand gap non doped Substrat 250 Å of Al(0.23)Ga(0.77)As
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Wafer and others layers
Fabrication photoresist Wafer and others layers
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Wafer and others layers
Fabrication Mask Photoresist Wafer and others layers
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Fabrication Mask photoresist
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Fabrication metal GaAs photoresist Layers
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Source Drain CAP small doped gap Schottky contact grand gap non doped Carrier donor layer grand gap doped Spacer grand gap non doped Canal small gap non doped Buffer grand gap non doped Substrat
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Fabrication 3 layers: PPMA(polypropylmethacrylate)
PPMA for the bottom layer PMIPK for the middle layer PPMA for the top layer PPMA(polypropylmethacrylate) PMIPK(polymethylisopropenylketone)
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Fabrication Using deep UV lithography
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Research Lattice matching
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