Understanding Pentavalent Elements and Semiconductor Doping

Semiconductor doping is a process where impurities are added to an intrinsic (pure) semiconductor material, like silicon or germanium, to alter its electrical conductivity. This process creates extrinsic semiconductors, which can be either p-type or n-type, depending on the type of impurity added.

There are two main types of dopants:

1. Trivalent Impurities: These elements have 3 valence electrons. When added to a tetravalent semiconductor (like silicon with 4 valence electrons), they create a "hole" (absence of an electron) in the crystal lattice, leading to p-type semiconductors. Examples include Boron, Aluminum, Gallium, and Indium (Group 13 elements).

2. Pentavalent Impurities: These elements have 5 valence electrons. When added to a tetravalent semiconductor, four of their valence electrons form covalent bonds with the semiconductor atoms, and the fifth electron is loosely bound and becomes a free electron, increasing conductivity. These impurities "donate" electrons and create n-type semiconductors. Examples include Phosphorus, Arsenic, and Antimony (Group 15 elements).

The question asks to identify a pentavalent element from the given options that is used for doping semiconductors.

Analyzing the Options

Let's examine each option based on its position in the periodic table and its valency:

• Aluminum (Al): Aluminum is in Group 13 (IIIA) of the periodic table. Elements in Group 13 typically have 3 valence electrons. Therefore, Aluminum is a trivalent element.

• Antimony (Sb): Antimony is in Group 15 (VA) of the periodic table. Elements in Group 15 typically have 5 valence electrons. Therefore, Antimony is a pentavalent element.

• Indium (In): Indium is in Group 13 (IIIA) of the periodic table. Elements in Group 13 typically have 3 valence electrons. Therefore, Indium is a trivalent element.

• Boron (B): Boron is in Group 13 (IIIA) of the periodic table. Elements in Group 13 typically have 3 valence electrons. Therefore, Boron is a trivalent element.

We can summarize this information in a table:

From the analysis, Antimony is the only pentavalent element among the given options. Pentavalent elements like Antimony are commonly used as donor impurities to create n-type semiconductors.

Conclusion

Based on the valency and common doping practices, Antimony is a pentavalent element used for doping semiconductors.

Revision Table: Semiconductor Doping Elements

Additional Information: Semiconductor Types

Let's briefly look at the types of semiconductors:

• Intrinsic Semiconductor: This is a pure semiconductor material (like Si or Ge) with no impurities. Its conductivity is low and depends primarily on temperature.

• Extrinsic Semiconductor: This is a semiconductor material that has been doped with impurities to increase its conductivity. There are two types:

  • n-type Semiconductor: Created by doping with pentavalent impurities. The majority charge carriers are electrons, and minority carriers are holes. The extra electron from the pentavalent atom acts as a donor.

  • p-type Semiconductor: Created by doping with trivalent impurities. The majority charge carriers are holes, and minority carriers are electrons. The trivalent atom creates a vacancy (hole) that can accept an electron, thus acting as an acceptor.

The addition of even a small amount of dopant atoms (e.g., 1 atom per $10^6$ or $10^8$ semiconductor atoms) can significantly increase the conductivity of the semiconductor material, which is fundamental to creating electronic devices like diodes and transistors.