Conductivity

Definition

Conductivity is a measure of a material's ability to conduct electric current, often represented by the symbol $$ au$$. In semiconductors, conductivity is influenced by the concentration and mobility of charge carriers such as electrons and holes. Understanding conductivity is essential for differentiating between intrinsic and extrinsic semiconductors, analyzing how temperature affects carrier concentration, and designing effective ohmic contacts for device performance.

5 Must Know Facts For Your Next Test

1. Intrinsic semiconductors have a low level of conductivity due to the limited number of charge carriers at absolute zero, which increases with temperature as more electrons are thermally excited.
2. Extrinsic semiconductors are doped with impurities to increase conductivity by introducing additional charge carriers, either electrons (n-type) or holes (p-type).
3. Temperature has a significant impact on conductivity; as temperature increases, the thermal energy can promote more charge carriers into the conduction band, enhancing conductivity.
4. Ohmic contacts are crucial for ensuring that the conductivity of a semiconductor device is maintained across junctions without introducing significant resistance.
5. The relationship between conductivity, carrier concentration, and mobility can be expressed with the formula $$ au = n imes q imes ext{mobility}$$, where $$n$$ is the carrier concentration and $$q$$ is the charge of an electron.

Review Questions

• How does the difference in conductivity between intrinsic and extrinsic semiconductors impact their applications in electronic devices?
  • Intrinsic semiconductors have lower conductivity due to fewer charge carriers, making them less suitable for many applications unless modified by temperature changes. In contrast, extrinsic semiconductors, which are doped to increase charge carrier concentration, offer much higher conductivity and are critical for designing devices like transistors and diodes. Understanding this difference helps in selecting materials for specific functions in electronics.
• What role does temperature play in influencing the conductivity of semiconductor materials, and how does this relate to practical applications?
  • Temperature significantly affects the conductivity of semiconductors by increasing the energy available to electrons, allowing more of them to jump into the conduction band. This increased carrier concentration enhances conductivity, which is vital for devices like sensors and thermistors that rely on temperature variations. Understanding this relationship helps engineers design systems that operate effectively across different temperatures.
• Evaluate how the concept of ohmic contacts relates to overall device performance in semiconductor technology, especially regarding conductivity.
  • Ohmic contacts play a crucial role in semiconductor devices by ensuring low-resistance pathways for current flow between the semiconductor and metal contacts. If these contacts are not well-designed, they can introduce significant resistance that hampers performance, reducing the effectiveness of the device. This relationship underscores the importance of achieving high conductivity not only in the semiconductor material itself but also at all interfaces within the device.

Related terms

Carrier Concentration:

The number of charge carriers (electrons or holes) per unit volume in a semiconductor, directly affecting its conductivity.

Mobility:

The measure of how quickly charge carriers can move through a semiconductor when an electric field is applied, impacting overall conductivity.

Ohmic Contact:

A type of electrical junction that allows current to flow easily in both directions, ensuring low resistance and efficient charge transfer.