A semiconductor is formed by ________ bonds.

Question

Examoogle · Accepted Answer

Covalent

Explanation: Semiconductors like Silicon and Germanium are Group-IV elements that attain stable octet configurations by sharing valence electrons with neighboring atoms. This process of electron sharing between atoms results in the formation of covalent bonds, which create the crystalline lattice structure.

Working Principle: In a crystal lattice (e.g., Diamond structure), each semiconductor atom has 4 valence electrons. It shares each of these with 4 adjacent atoms to form 4 strong covalent bonds. At $T = 0 K$, all covalent bonds are intact, behaving as insulators. As temperature increases or energy is supplied, some covalent bonds break, releasing charge carriers (electrons and holes) that allow for electrical conduction.

Key Formulas: $E_g = E_c - E_v$ — Energy gap between Conduction Band ($E_c$) and Valence Band ($E_v$); $n_i^2 = n cdot p$ — Mass Action Law for semiconductor carrier concentration

Key Points: Group-IV elements (Si, Ge) form stable crystals via covalent bonding.; Breaking a covalent bond generates an electron-hole pair.; Covalent bonds are essential for maintaining the semiconductor crystal geometry.; Intrinsic semiconductors conduct only when thermal energy exceeds the bandgap energy.

Advantages: Provides structural stability to the crystalline lattice.; Allows control over charge carrier density via doping.

Disadvantages: At absolute zero temperature ($0 K$), the covalent bond structure acts as a perfect insulator.; High thermal sensitivity compared to metals due to bond-breaking energy requirement.

Applications: Fabrication of P-N junction diodes.; Development of Transistors (BJT, FET) and Integrated Circuits (ICs).

Additional Info: Electrovalent (Ionic) bonds occur due to electrostatic attraction between ions, typically seen in salts like $NaCl$.. Co-ordinate bonds involve a shared pair of electrons donated by only one of the participating atoms, which is not the primary mechanism in pure semiconductor crystals.

Answer: A is correct — Semiconductor crystals are held together by covalent bonds formed through the sharing of valence electrons between adjacent atoms.

Exam Tip: Remember that intrinsic semiconductors act as insulators at $0 K$ because all covalent bonds are completely filled, leaving no free electrons for conduction.

Related Questions

Discussion (0)