The difference between an insulator and a semiconductor is
Right Answer is:
All of the above
The main difference between an insulator and a semiconductor are
- Forbidden gap
- Number of free electrons
- Atomic structure
- An insulator has a wider forbidden gap as compared to semiconductors.
- The number of free electrons is less in insulators.
- The atomic structure of the insulator and conductor is different.
⇒ In an insulator, the lower band is fined with electrons and the higher band is empty at 0 K.
⇒ The lower, filled band is called the valence band, and the upper, empty band is the conduction band.
⇒ In an insulator, the energy gap between the valence band and conduction band is very large and approximately equal to 5 eV.
⇒ Therefore, very high energy is required to push the electrons to the conduction band.
⇒ For these reasons the electrical conductivity of the insulator is extremely small and may be regarded as nil under ordinary conditions (room temperature).
⇒ Semiconductors have the same type of band structure as an insulator; but the energy gap is much smaller, on the order of 1 eV.
⇒ At low temperature, the valence band of a semiconductor is completely filled and the conduction band is completely empty.
⇒ Therefore, a semiconductor virtually behaves like an insulator at low temperatures. However, at room temperature, some electrons cross over to the conduction band giving little conductivity to the semiconductor.
⇒ As the temperature is increased more valence electrons cross over to the conduction band and conductivity increases.
⇒ This shows that the electrical conductivity of a semiconductor increases with the increase of temperature, i.e., a semiconductor has a negative temperature coefficient of resistance.
The degree of conductivity is determined as follows:
1. Atoms with fewer than four valence electrons are good conductors.
2. Atoms with more titian four valence electrons are poor conductors.
3. Atoms with four valence electrons are semiconductors.