A semiconductor is formed by?

1. Analyze the question

The question asks for the type of chemical bonding responsible for the structure of a semiconductor. Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator.

2. Explain the concept

Semiconductors, such as Silicon (Si) and Germanium (Ge), belong to Group IV of the periodic table. Each atom in a semiconductor crystal has four valence electrons. To achieve a stable octet configuration, each atom shares its four valence electrons with four neighboring atoms. This sharing of electrons creates a strong, stable lattice structure known as a covalent bond.

In these materials, the electrons are held firmly in these bonds at absolute zero temperature, making the material an insulator. However, as temperature increases or through a process called "doping," these covalent bonds can be broken, releasing electrons that allow the material to conduct electricity.

3. Show the solution

• Electrovalent (Ionic) bonds involve the transfer of electrons, which is characteristic of salts like NaCl, not semiconductors.
• Co-ordinate (Dative) bonds involve one atom donating a lone pair of electrons to another, which is not the primary structure of elemental semiconductors.
• Covalent bonds involve the sharing of electron pairs between atoms. In a silicon crystal, every silicon atom is covalently bonded to four other silicon atoms, forming the tetrahedral structure that defines the semiconductor.

Therefore, the crystalline structure of a semiconductor is held together by covalent bonds.

4. Identify the answer

The correct option is D.

5. Exam Tip

When you see questions about semiconductors in JAMB, always remember the "Group IV" rule. Elements in Group IV (Silicon, Germanium) are the most common semiconductors, and they always form covalent bonds to create their crystal lattice. If you are asked about "doping," remember that it involves adding impurities to these covalent structures to increase conductivity!