Question
Explain electricity conduction in intrinsic semi-conductors.
✓
Answer
→As shown in Fig. (a), Suppose there is a hole at site-1. The movement of holes can be visualised as shown in the Fig (b).
→An electron from the covalent bond at site-2, may jump to the vacant site-1. (hole)
→Thus, after such a jump, the hole is at site-2 and the site-1 has now an electron. Therefore, apparently, the hole has moved from site-1 to site-2. (So, the directions of motion of a hole and an electron are opposite).
→Note that the electron originally set free (Fig. a) is not involved in the process of hole motion.
→The free electron moves completely independently as conduction electron and gives rise to an electron current, I under an applied electric field.
→Remember that the motion of hole is only a convenient way of describing the actual motion of bound electrons, whenever there is an empty bond anywhere in the crystal.
→Under the action of an electric field, these holes move towards negative potential giving the hole current, $I _h$.
→The total current, I is thus the sum of electron current $I _e$ and the hole current $I _h$ :
$\therefore I = I _e+ I _h$ .......(1)
→Apart from the process of generation of conduction electrons and holes, a simultaneous process of recombination occurs in which these electrons recombine with holes.
→At equilibrium, the rate of generation is equal to the rate of recombination of charge carries. The recombination occurs due to an electron colliding with a hole.
→An electron from the covalent bond at site-2, may jump to the vacant site-1. (hole)
→Thus, after such a jump, the hole is at site-2 and the site-1 has now an electron. Therefore, apparently, the hole has moved from site-1 to site-2. (So, the directions of motion of a hole and an electron are opposite).
→Note that the electron originally set free (Fig. a) is not involved in the process of hole motion.
→The free electron moves completely independently as conduction electron and gives rise to an electron current, I under an applied electric field.
→Remember that the motion of hole is only a convenient way of describing the actual motion of bound electrons, whenever there is an empty bond anywhere in the crystal.
→Under the action of an electric field, these holes move towards negative potential giving the hole current, $I _h$.
→The total current, I is thus the sum of electron current $I _e$ and the hole current $I _h$ :
$\therefore I = I _e+ I _h$ .......(1)
→Apart from the process of generation of conduction electrons and holes, a simultaneous process of recombination occurs in which these electrons recombine with holes.
→At equilibrium, the rate of generation is equal to the rate of recombination of charge carries. The recombination occurs due to an electron colliding with a hole.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
More "2 Marks Questions" from SEMICONDUCTOR ELECTRONICS: MATERIALS, DEVICES AND SIMPLE CIRCUITS→SEMICONDUCTOR ELECTRONICS: MATERIALS, DEVICES AND SIMPLE CIRCUITS — all question types→Physics STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→
Similar questions
Two vectors have magnitudes 2m and 3m. The angle between them is 60°. Find:
- The scalar product of the two vectors.
- The magnitude of their vector product.
Name the nucleus for which the binding energy per nucleon is maximum.
How magnetic field lines are drawn? Write their four characteristics.
$\ce{He_2^3}$ and $\ce{He_1^3}$ nuclei have the same mass number. Do they have the same binding energy?a
→What is the importance of binding energy per nucleon ?
A point source is placed at a depth h below the surface of water (refractive index = μ).
- Show that light escapes through a circular area on the water surface with its centre directly above the point source.
- Find the angle subtended by a radius of the area on the source.
The light emitted in the transition $n = 3$ to $n = 2$ in hydrogen is called $\text{H}_\alpha$ light. Find the maximum work function a metal can have so that $\text{H}_\alpha$ light can emit photoelectrons from it.
→Sound with intensity larger than $120\ dB$ appears painful to a person. A small speaker delivers $2.0W$ of audio output. How close can the person get to the speaker without hurting his ears?
→A book is lifted from the floor and is kept in an almirah. One person says that the potential energy of the book is increased by 20J and the other says it is increased by 30J. Is one of them necessarily wrong?
Can virtual image be formed on the retina in a seeing process?