Notes about intrinsic and extrinsic semiconductor?

- Intrinsic semiconductors are pure semiconducting materials, such as silicon or germanium, with no added impurities. They have a low conductivity at room temperature.
- Extrinsic semiconductors are doped with impurities to increase their conductivity. This can be done by adding elements like phosphorus or boron to silicon or germanium.
- Intrinsic semiconductors have an equal number of electrons and holes, resulting in a low conductivity. Extrinsic semiconductors have an excess of either electrons (n-type) or holes (p-type), which increases their conductivity.
- The conductivity of intrinsic semiconductors can be increased by heating them, which generates more electron-hole pairs. Extrinsic semiconductors have a higher conductivity due to the presence of dopant atoms.
- Extrinsic semiconductors are commonly used in electronic devices, as their conductivity can be easily controlled by adjusting the doping level. Intrinsic semiconductors are used in some specialized applications, such as high-temperature sensors.

Intrinsic Semiconductor

- Pure semiconductor material with no impurities or defects
- Electrons and holes are generated in equal numbers by thermal energy
- Conductivity due to intrinsic carriers
- Number of electron-hole pairs increases with temperature
- No external bias required
- Example: Silicon at room temperature

Extrinsic Semiconductor

- Semiconductor material doped with impurities
- Impurities create additional energy levels within the semiconductor
- Two types:

N-Type Extrinsic Semiconductor

- Impurities are dopants with pentavalent atoms (e.g., arsenic, phosphorus)
- Donates extra electrons to the semiconductor
- Majority carriers are electrons
- Minority carriers are holes

P-Type Extrinsic Semiconductor

- Impurities are dopants with trivalent atoms (e.g., boron, indium)
- Creates electron deficiency or holes in the semiconductor
- Majority carriers are holes
- Minority carriers are electrons

Characteristics of Extrinsic Semiconductors:

- Increased conductivity compared to intrinsic semiconductors
- Conductivity is influenced by the type and concentration of impurities
- Can be controlled by external bias
- Used in electronic devices such as diodes and transistors

Comparison:

| Feature | Intrinsic Semiconductor | Extrinsic Semiconductor |
|---|---|---|
| Impurities | None | Dopants present |
| Conductivity | Due to intrinsic carriers | Due to extrinsic carriers |
| Carrier Concentration | Equal number of electrons and holes | Majority carriers dominate |
| Temperature Dependence | Conductivity increases with temperature | Conductivity decreases with temperature |
| External Bias | Not required | Required for majority carrier flow |
| Applications | Research, semiconductor physics | Electronic devices