CBSE 2025 · Region 4 · Set 1 · Q28 · 3 marks
(a)What are majority and minority charge carriers of p-type and n-type semiconductors?(b)Explain briefly the formation of diffusion current and drift current in a p-n junction diode.
(a)
What are majority and minority charge carriers of p-type and n-type semiconductors?
(b)
Explain briefly the formation of diffusion current and drift current in a p-n junction diode.
Marking-scheme solution
(a)
In p-type semiconductor:
Majority charge carriers – holes
Minority charge carriers – electrons
In n-type semiconductors:
Majority charge carriers – electrons
Minority charge carriers – holes
(b)
Diffusion current – during the formation of a p-n junction, due to the concentration gradient across p and n sides, holes diffuse from p side to n side ($\displaystyle p \rightarrow n$) and electrons diffuse from n side to p side ($\displaystyle n \rightarrow p$). This motion of charge carriers gives rise to diffusion current across the junction.
Drift current – due to the electric field at the junction, an electron on the p side of the junction moves to the n side and a hole on the n side of the junction moves to the p side. This motion of charge carriers due to the electric field gives drift current.
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