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#band gap

3 public questions tagged with this topic.

Semiconductors, Types and Energy Bands

Which property distinguishes insulators from semiconductors?

**Semiconductor properties** distinguish from conductors and insulators by temperature dependence and doping response. At 0 K intrinsic acts as insulator, conductivity due to thermally generated electron-hole pairs, number of outer electrons 4 for Si/Ge forming covalent bonds, each atom shares electrons, crystal with N atoms has 4N valence electrons, 2N bonds. Insulators have a large energy gap ( E_g > 3 eV ), preventing electron excitation, while semiconductors have a smaller gap ( 0.2 eV to 3 eV ), allowing some conduction. Substituting values gives Energy gap, which matches expected behavio

Ref: NCERT > Physics Book > Electronic Devices > Semiconductors, Types and Energy Bands

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Semiconductors, Types and Energy Bands

Which of the following has the highest energy gap?

**Energy bands in semiconductors** consist of valence band filled at 0 K and conduction band empty, gap E_g small ~1 eV (Si 1.1 eV, Ge 0.7 eV), insulators large gap >3 eV (C diamond 5.4 eV), conductors overlapping. Intrinsic semiconductor at 0 K behaves as insulator because no thermal excitation, at T>0 K electrons jump to conduction band leaving holes, conductivity increases with temperature. Energy gaps: C (diamond) = 5.4 eV, Si = 1.1 eV, Ge = 0.7 eV, Sn = 0 eV (metal). Carbon has the highest energy gap among these, making it an insulator. Substituting values gives C, which matches expected

Ref: NCERT > Physics Book > Electronic Devices > Semiconductors, Types and Energy Bands

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Semiconductors, Types and Energy Bands

Why is carbon an insulator while silicon and germanium are semiconductors?

**Types of semiconductors** elemental Si, Ge group IV with 4 valence electrons, compound GaAs, InP etc. Intrinsic has n_e = n_h, extrinsic doped with pentavalent donors (P, As) gives n-type excess electrons, trivalent acceptors (B, Al) gives p-type excess holes, resistivity range semiconductors 10⁻⁵ to 10⁶ Ω·m vs insulators 10¹¹ Ω·m. Carbon (diamond) has a large energy gap (5.4 eV), preventing electron excitation at room temperature, while Si (1.1 eV) and Ge (0.7 eV) have smaller gaps, allowing thermal excitation and conduction. Substituting values gives Carbon has a larger energy gap, which m

Ref: NCERT > Physics Book > Electronic Devices > Semiconductors, Types and Energy Bands

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