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प्रश्न
Sn, C, and Si, Ge are all group XIV elements. Yet, Sn is a conductor, C is an insulator while Si and Ge are semiconductors. Why?
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उत्तर
The conduction level of any element depends on the energy gap between its conduction band and valence band.
In conductors, there is no energy gap between the conduction band and valence band. For insulators, the energy gap is large and for semiconductors the energy gap is moderate.
The energy gap for Sn is 0 eV, for C is 5.4 eV, for Si is 1.1 eV and for Ge is 0.7 eV related to their atomic size.
Therefore Sn is a conductor, C is an insulator, and Ge and Si are semiconductors.
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संबंधित प्रश्न
Distinguish between 'intrinsic' and 'extrinsic' semiconductors
Distinguish between intrinsic and extrinsic semiconductor. (Give any two points).
In a p-type semiconductor, the acceptor impurity produces an energy level ______
A donor impurity results in ______.
In n-type semiconductor majority carriers and minority carriers are respectively ______.
The electron and hole concentration in a semiconductor in thermal equilibrium is given by ______.
State how a p-type semiconductor will be obtained from a pure crystal of a semiconductor.
Explain the following term:
Extrinsic semiconductor
Distinguish between n-type and p-type semiconductors.
The conductivity of a semiconductor increases with increase in temperature because ______.
Why are elemental dopants for Silicon or Germanium usually chosen from group XIII or group XV?
Suppose a ‘n’-type wafer is created by doping Si crystal having 5 × 1028 atoms/m3 with 1 ppm concentration of As. On the surface 200 ppm Boron is added to create ‘P’ region in this wafer. Considering n i = 1.5 × 1016 m–3, (i) Calculate the densities of the charge carriers in the n and p regions. (ii) Comment which charge carriers would contribute largely for the reverse saturation current when diode is reverse biased.
The figure shows a piece of pure semiconductor S in series with a variable resistor R and a source of constant voltage V. Should the value of R be increased or decreased to keep the reading of the ammeter constant, when semiconductor S is heated? Justify your answer
Two crystals C1 and C2, made of pure silicon, are doped with arsenic and aluminium respectively.
Identify the extrinsic semiconductors so formed.
Name the extrinsic semiconductors formed when pure germanium is doped with a trivalent impurity. Draw the energy band diagram of extrinsic semiconductors so formed.
Name the extrinsic semiconductors formed when pure germanium is doped with a Pentavalent impurity. Draw the energy band diagram of extrinsic semiconductors so formed.
- Statement I: By doping silicon semiconductor with pentavalent material, the electrons density increases.
- Statement II: The n-type semiconductor has net negative charge. In the light of the above statements, choose the most appropriate answer from the options given below:
Pieces of copper and of silicon are initially at room temperature. Both are heated to temperature T. The conductivity of ______.
- Assertion (A): Putting the p-type semiconductor slab directly in physical contact with the n-type semiconductor slab cannot form the pn junction.
- Reason (R): The roughness at contact will be much more than inter atomic crystal spacing and continuous flow of charge carriers is not possible.
