In a semiconductor either it may be p-type or n-type there exists some of the majority and the minority charge carriers. As the p-type and n-type present on a single crystal at the center, there is the formation of the p-n junction. The basic device formed because of the above process is the p-n junction diode. We cover the basic differences between Drift Current and Diffusion Current below with a comparison table.
In the p-n junction diode if it is doped non-uniformly then there exists a movement of charge carriers from higher concentration to lower concentration. This results in the recombination of the carriers and leads to the process of diffusion. Another process occurs is the drift of the charge carriers. It is based on the applied electric field.
Difference Between Drift and Diffusion Current
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Drift Current |
Diffusion Current |
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(1) The random motion of charge carriers is stopped in semiconductors due to the application of electric field ad drift takes place. The current generated in the process is known as Drift Current. |
(1)If the concentration of the carriers differs then there exists concentration gradient. In order to overcome this and attain an equilibrium state, the process of diffusion takes place. The current generated due to this process is referred to as Diffusion Current. |
| (2) Drift current is generated based on the applied electric field. |
(2) It doesn’t require any external electric field some amount of any external energy is sufficient for the process. |
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(3) It gets influenced by the application of external electric field and the charge carrier concentration. |
(3)It is dependent on the recombination of charge carriers so that it gets easily influenced by the rate of charge carrier concentration per unit length. |
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(4)Drift current obeys the ohms law. |
(4) It obeys Fick’s law. |
| (5) The holes and electron direction will be opposite to each other.
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(5)For holes and electrons, the diffusion densities are opposite in sign to each other.
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(6) The direction of the electric field and the drift current will be in the same direction. |
(6) The slope of carrier concentration decides the direction of the diffusion current. |
Points to Remember:
(1) The drift current is because of the electric field or external supply applied on it and the diffusion is because of non-uniformity of the charge carriers and to attain the uniformity without any application of external supply.
(2) drift current and electric field that is applied will be in the same direction. Where the diffusion current direction is decided by the slope of the concentration gradient. But the overall current density is the sum of the drift and diffusion currents.
The drift and the diffusion both are the important process occurred in the semiconductor once the doping is done. It is not compulsory that both should occur at one time. After the process of drift and diffusion occurred is responsible for the generation of currents in the circuit. But at the condition of equilibrium sum of the drift and diffusion currents that is the total current density must be zero. Then is it any possibility of occurrence of both the process occurring at one time?