Advertisements
Advertisements
Question
Distinguish between 'intrinsic' and 'extrinsic' semiconductors
Solution
| Intrinsic Semiconductor | Extrinsic Semiconductor |
| It is a pure semiconductor material with no impurity atoms in it. | It is prepared by doping a small quantity of impurity atoms to the pure semiconductor. |
| The number of free electrons in the conduction band and the number of holes in valence band is exactly equal. | The number of free electrons and holes is never equal. There is an excess of electrons in n-type semiconductors and an excess of holes in p-type semiconductors. |
APPEARS IN
RELATED QUESTIONS
Semiconductors formed by doping germanium (Ge) with aluminium (Z = 13) and antimony (Z = 51) are ______.
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.
Two crystals C1 and C2, made of pure silicon, are doped with arsenic and aluminium respectively.
Identify the extrinsic semiconductors so formed.
- 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.
