III V Semiconductor

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III / V Semiconductor
Common Building Block for X-Band T/R Modules
GaAs Wafers
ME J.V.D007
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Electron Energy Bands
Partially filled band
Conduction Band
Small Energy Gap
Large Energy Gap relative to kT
Valence Band
Conductor
Insulator
Semiconductor

• Energy Bands in materials determine the energy
  required to make electrons available for current
• Semiconductors are special materials that can be
  made to act as an insulator or a conductor
• Concept leads to Solid State Switches and
  Transistors

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Periodic Table
Number ofe- in outer shell
Filling Shells
K
L
M
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Velocity vs. Field for Some Semiconductors
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Current Flow In Semiconductor

• Current is just the net flow of charged
  particles, which we can express in one dimension
  for low fields as

q Electronic Charge m Mobility n Electron
Concentration p Hole Concentration D
Diffusion Constant e Electric Field

• With no concentration gradients, this leads us
  back to Ohms Law (VIR)

Interesting concept Holes
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Diode

• RF switching can be performed using high
  performance P-I-N diodes

ID a exp( VA )
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Transistors

• Types of Transistors
• Field Effect Trans. (FETs)
• Bipolar Transistors

• Transistor Applications
• Logic
• Amplification (Low Noise, Driver, Power)
• Freq. Mixing / Doubling
• Signal Generation
• A/D D/A conversion
• Signal Processing

General FET Characteristics
DRAIN-SOURCE VOLTAGE
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Transistor Gate Metal
Key take away is how small this gate structure
really is lt 250nm
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T/R Module Made of Small Things