Semiconductor Physics
Energy bands, intrinsic and extrinsic material, doping and charge carriers.
In a solid, electron energies form bands. The valence band is full; the conduction band above it is where electrons can move freely. The gap between them is the band gap :
| Material | (eV) |
|---|---|
| Germanium | 0.67 |
| Silicon | 1.12 |
| Gallium arsenide | 1.42 |
| Silicon carbide (4H) | 3.26 |
| Gallium nitride | 3.4 |
Insulators have large gaps, conductors have overlapping bands, and semiconductors sit in between — heat or light can lift some electrons across the gap.
Sub-topics (2)
Intrinsic and Extrinsic Semiconductors
Pure silicon conducts poorly; adding dopant atoms creates n-type or p-type material with many more carriers.
Drift and Diffusion Current
Carriers move by drift (pushed by an electric field) and diffusion (spreading from high to low concentration).
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