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Why is boron added to germanium semiconductors?

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A labeled diagram of the periodic table entry for boron shows its atomic number 5, symbol B, electron configuration, atomic weight range, and classification as a solid, weakly acidic, other nonmetal with a rhombohedral crystal structure at room temperature. — boron Properties of boron.

Boron is added to germanium semiconductors as a dopant to modify the material's electrical conductivity.12

Because boron atoms have only three electrons available for bond formation—compared to the four electrons shared by germanium atoms in a crystalline lattice—the addition of boron creates a positively charged site known as a "hole". This hole acts as a charge carrier, allowing electrical conduction to occur through the migration of these positive sites. Consequently, germanium doped with boron is classified as p-type (positive-type) semiconductor material.1