Donor impurities

Definition

Donor impurities are foreign atoms added to a semiconductor material that provide extra electrons, enhancing its electrical conductivity. These impurities, typically from group V elements, create energy levels within the band gap that facilitate the movement of electrons, effectively increasing the number of charge carriers in the semiconductor. This doping process is crucial for the performance of various electronic devices, allowing for better control of electrical properties.

5 Must Know Facts For Your Next Test

1. Common donor impurities include phosphorus (P), arsenic (As), and antimony (Sb), which donate extra electrons to the conduction band of silicon or germanium semiconductors.
2. When donor impurities are added, they create additional energy states close to the conduction band, making it easier for electrons to jump into the conduction band at room temperature.
3. The level of doping can significantly affect the carrier concentration, allowing for tailored electrical properties for specific applications in electronics.
4. Donor impurities enable the creation of n-type semiconductors, where the majority charge carriers are negatively charged electrons, contrasting with p-type semiconductors created by acceptor impurities.
5. Understanding donor impurities is essential for designing and fabricating semiconductor devices such as diodes, transistors, and integrated circuits.

Review Questions

• How do donor impurities affect the electrical conductivity of semiconductors?
  • Donor impurities enhance the electrical conductivity of semiconductors by introducing extra electrons into the material. When foreign atoms like phosphorus are added, they provide energy levels close to the conduction band, allowing electrons to easily move into that band. This increase in free charge carriers leads to improved conductivity and is essential for developing efficient electronic devices.
• Compare and contrast donor and acceptor impurities in terms of their effects on semiconductor properties.
  • Donor impurities add extra electrons to a semiconductor, creating n-type materials with negative charge carriers as the majority. In contrast, acceptor impurities create holes by accepting electrons, leading to p-type materials where holes are the majority charge carriers. Both types of doping are vital for controlling electrical properties, but they influence conductivity in opposite ways—donors increase electron concentration while acceptors increase hole concentration.
• Evaluate the role of donor impurities in modern electronic devices and how they influence their functionality.
  • Donor impurities play a critical role in modern electronic devices by enabling precise control over semiconductor behavior. The ability to adjust carrier concentrations through doping allows engineers to design components like transistors and diodes with specific characteristics needed for applications in computing and telecommunications. This manipulation directly influences device efficiency, switching speeds, and overall performance, making understanding donor impurities fundamental in electronics engineering.

Related terms

Acceptor impurities: Acceptor impurities are foreign atoms that create 'holes' by accepting electrons, which can also increase the conductivity of a semiconductor but in a different way compared to donor impurities.

Doping: Doping is the intentional introduction of impurities into a semiconductor to modify its electrical properties, such as enhancing conductivity through donor or acceptor types.

Band gap: The band gap is the energy difference between the valence band and the conduction band in a semiconductor, which determines its electrical and optical properties.