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Reverse bias applied to a junction diode

Asked in CBSE AIPMT 2003 · Depletion region and barrier potential

• (1) lowers the potential barrier
• (2) raises the potential barrier
• (3) increases the majority carrier current
• (4) increases the minority carrier current

Step-by-step solution

Why the other options are wrong

• (1) comes from lowering the barrier is what forward bias does; a reverse bias is applied in the same sense as the built-in field, not against it.
• (3) comes from reverse bias pulls majority carriers away from the junction rather than towards it, so the majority carrier current is all but cut off.
• (4) comes from there is a grain of truth here, since the small reverse current is indeed carried by minority carriers. But it saturates almost at once: how many minority carriers there are to collect is set by thermal generation, not by the applied voltage, so raising the bias barely changes the current. That is why it is called the reverse saturation current, and why 'increases' does not describe it.

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