Advertisements
Advertisements
प्रश्न
In a semiconductor,
(a) there are no free electrons at 0 K
(b) there are no free electrons at any temperature
(c) the number of free electrons increases with temperature
(d) the number of free electrons is less than that in a conductor.
उत्तर
(a) there are no free electrons at 0 K
(c) the number of free electrons increases with temperature
(d) the number of free electrons is less than that in a conductor
In semiconductors, the valence band is full at 0 K, but the conduction band is empty. So, no free electron is available for conduction at 0 K.
As the temperature increases, covalent bonds that provide free charge carriers for conduction in a semiconductor break.
As the conduction band in metals is already partially filled at 0 K, many free electrons below the Fermi level acquire energy from an external source or temperature, jump to the conduction band and start behaving like free electrons. Hence, metals contain more free electrons than semiconductors.
APPEARS IN
संबंधित प्रश्न
Distinguish between a conductor and a semi conductor on the basis of energy band diagram
What is the resistance of an intrinsic semiconductor at 0 K?
A p-type semiconductor is
An incomplete sentence about transistors is given below:
The emitter−..... junction is __ and the collector−..... junction is __. The appropriate words for the dotted empty positions are, respectively,
A semiconductor is doped with a donor impurity.
Let ΔE denote the energy gap between the valence band and the conduction band. The population of conduction electrons (and of the holes) is roughly proportional to e−ΔE/2kT. Find the ratio of the concentration of conduction electrons in diamond to the in silicon at room temperature 300 K. ΔE for silicon is 1.1 eV and for diamond is 6.1 eV. How many conduction electrons are likely to be in one cubic metre of diamond?
With reference to Semiconductor Physics,
Draw a labelled energy band diagram for a semiconductor.
Hydrogen atom in n = 3 state has a lifetime of 10-10 sec. The number of revolutions an electron makes in the n = 3 state before returning to the ground state is ______.
Useful data
`1/(4pi∈_0) = 8.99 xx 10^-34`N m2 C-2; e = 1.60 10-19 C; h = 6.63 10-34 Js; me = 9 × 10-3 kg
An n-type semiconductor is
For germanium crystal, the forbidden gas energy gap
A semiconductor is cooled from T.K to T2K its resistance will
The valance of an impurity added to germanium crystal in order to convert it into p-type semiconductor is
In a common base configuration Ie = 1 mA α = 0.95 the value of base current is
The reaction between α and β parameter of a transistor is given by
Hole are majority charge carrier in
Draw the energy band diagrams for conductors, semiconductors and insulators. Which band determines the electrical conductivity of a solid? How is the electrical conductivity of a semiconductor affected with rise in its temperature? Explain.
Which one of the following elements will require the highest energy to take out an electron from them?
Pb, Ge, C and Si
With reference to semiconductor physics, answer the following question.
What is meant by “Forbidden band" of energy levels?
