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Chapter III Semiconductor Devices. 半導體元件. Basic Building Blocks of Semiconductor Devices. ( a) M-S Junction (b) P-N Junction (c) Heterojuction (d) MOS structure. Metal-Semiconductor Contact. Schottky contact Rectifying contact Schottky Barrier M-S devices Unipolar devices

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Chapter iii semiconductor devices

Chapter IIISemiconductor Devices

半導體元件


Basic building blocks of semiconductor devices
Basic Building Blocks of Semiconductor Devices

(a) M-S Junction (b) P-N Junction (c) Heterojuction (d) MOS structure


Metal semiconductor contact
Metal-Semiconductor Contact

  • Schottky contact

    • Rectifying contact

    • Schottky Barrier

    • M-S devices

    • Unipolar devices

    • High-speed devices

  • Ohmic contact

    • Non-rectifying contact

    • Specific contact resistance

    • The apace charge width in a M-S contact is inversely proportional to the square root of the semiconductor doping.The probability of tunneling through the barrier increases with the increasing doping concentration.

    • Electrodes

Energy-band diagram of a heavily doped n-semiconductor-to-metal junction


Schottky barrier diode
Schottky-Barrier Diode

  • M-S junction device

  • Unipolar device

  • Majority-carrier device

  • Without minority- carrier-storage effect

  • III-V compound semiconductors (GaAs)

  • Properities of devices:

    • High operation speed

    • Lower cut-in voltage

    • Higher saturation current


The p n diode under thermal equilibrium
The P-N Diode --- Under Thermal Equilibrium

P-type and N-type semiconductors before and after the junction formed

A p-n junction with abrupt doping charges at the metallurgical junction


The p n diode under biasing conditions
The P-N Diode --- Under Biasing Conditions

Current-voltage characteristics of a typical Si p-n junction

  • Thermal equilibrium

  • Forward-bias condition.

  • Reverse-bias condition


Classification of semiconductor devices
Classification of Semiconductor Devices

  • Bipolar Devices

    • P-N Junction Diode

    • Bipolar Junction Transistor (BJT)

    • Heterojunction Bipolar Transistor (HBT)

    • Thyristor and related power devices

  • Unipolar Devices

    • Schottky-barrier diode (SBD)

    • Junction Field Effect Transistor (JFET)

    • Metal-Oxide-Semiconductor FET (MOSFET)

    • MOS Diode (Capacitor)

    • Complementary MOS (CMOS)  BiMOS and BiCMOS

    • Power MOS

  • High-Speed Devices

    • Metal-Semiconductor FET (MESFET)

    • Modulation-Doped FET (MODFET), High-Electron-Mobility Transistor (HEMT)


Semiconductor devices continued
Semiconductor Devices (continued)

  • Microwave Devices

    • Tunnel diode

    • IMPATT diode

    • Transferred-Electron Device (TED)

    • Quantum-Effect Devices

    • Hot-Electron Devices

  • Photonic Devices

    • Light Emitting Diode (LED)

    • Semiconductor Laser (Laser Diode, LD)

    • Photodetector

      • Photodiode (PD), Avalanche Photodiode (APD)

      • Phototransistor (PT)

    • Solar Cell

    • Display Devices

      • Thin-Film Transistor LCD (TFT-LCD)

      • Organic Electroluminescence Display (OELD) or Organic Light Emitting Diode (OLED)


Semiconductor devices continued1
Semiconductor Devices (continued)

  • Integrated Devices

    • Passive Components

      • IC Resistor, IC Capacitor, IC Inductor

    • MOS Menory

      • Dynamic Random Access Memory (DRAM)

      • Static Random Access Memory (SRAM)

      • Nonvolatile Memory

      • Erasable-Programmable Read-Only Memory (EPROM)

      • Electrically Erasable-Programmable Read-Only Memory (EEPROM)

      • Flash Memory

      • Single-Electron Memory

  • MEMS devices





MESFET

Schottky Contact

Ohmic Contact

To minimize parasitic capacitances

Mesa Structure


MODFET

  • Modulation Doped FET

    • A thin undoped well bounded by two wider bandgap doped barrier

  • HFET (Heterojunction FET)

  • 2DEG FET or TEGFET,

  • SEDFET (Separately Doped FET)

  • Advantages:

    • Extremely high cutoff frequency and fast access time


HEMT

  • HEMT:

    • High Electron Mobility Transistor

    • 250,000 cm2/V-s at 77K

    • 2,000,000 cm2/V-s at 4K

  • Why HEMT?

    • In conventional MESFET:

      Channel doping carrier number 

      But mobility (impurity scattering)

       conductivity is limited (  = q n )

    • For HEMT:

      Sheet carrier density is as high as 1012 cm-2 (~1020cm-3 for 10-nm thick channel layer)


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