Understanding Intrinsic Semiconductors

An intrinsic semiconductor is a pure semiconductor material without any significant dopant species present. Its electrical conductivity is primarily determined by the atoms constituting the semiconductor crystal itself. In its pure form, the number of electrons in the conduction band is equal to the number of holes in the valence band. Common examples include Silicon ($\text{Si}$) and Germanium ($\text{Ge}$).

Analyzing the Options

Let's examine each option to determine which one fits the definition of an intrinsic semiconductor:

• Germanium ($\text{Ge}$): Germanium is an element in Group 14 of the periodic table. It has a diamond cubic crystal structure, similar to Silicon. Pure Germanium exhibits semiconductor properties and is a classic example of an intrinsic semiconductor. Its electrical conductivity at room temperature is moderate and highly dependent on temperature.
• Bismuth ($\text{Bi}$): Bismuth is a post-transition metal, located in Group 15. While it exhibits some unusual electronic properties (like being a diamagnetic and having low electron mobility), it is generally classified as a poor metal or metalloid, not typically considered an intrinsic semiconductor in the context of electronic devices like $\text{Si}$ or $\text{Ge}$.
• Boron ($\text{B}$): Boron is a metalloid in Group 13. It has a very large band gap and does not typically function as an intrinsic semiconductor on its own. Instead, Boron is commonly used as a dopant (specifically a p-type dopant) when added to Silicon to create extrinsic semiconductors.
• Antimony ($\text{Sb}$): Antimony is also a metalloid in Group 15. Like Boron, it is primarily used as a dopant in semiconductor manufacturing, typically creating n-type conductivity when added to materials like Silicon or Germanium. It is not an intrinsic semiconductor itself.

Semiconductor Classification Summary

Conclusion

Based on the analysis, Germanium ($\text{Ge}$) is the only material listed that is fundamentally known and used as an intrinsic semiconductor.