Acceptor Impurity Basics

An acceptor type impurity is added to a semiconductor material (like Silicon or Germanium) to create a p-type semiconductor. These impurities have fewer valence electrons than the semiconductor atoms.

Valency and Acceptor Impurities

• Semiconductor atoms like Silicon (Si) and Germanium (Ge) belong to Group IV, having 4 valence electrons.
• Acceptor impurities typically belong to Group III of the periodic table, possessing 3 valence electrons.
• When a Group III element is added, it forms covalent bonds with semiconductor atoms but lacks one electron to complete a bond, creating an electron deficiency known as a hole. This hole acts as a positive charge carrier.

Analyzing the Options

• Boron (B): Belongs to Group III and has 3 valence electrons. It is a classic acceptor impurity.
• Aluminium (Al): Also belongs to Group III and has 3 valence electrons, making it an acceptor impurity.
• Phosphorous (P): Belongs to Group V and has 5 valence electrons. It acts as a donor impurity, creating n-type semiconductors.
• Iron (Fe): A transition metal, not typically used as a standard Group III or V dopant to create p-type or n-type semiconductors.

Conclusion on Acceptor Type

Both Boron and Aluminium are acceptor impurities. Since Boron is provided as an option and fits the definition perfectly, it is the correct answer for an acceptor type impurity.