The barrier potential of an unbiased p-n junction diode is 0.6 V. A forward bias of 0.25 V is now applied across the diode. The effective barrier height becomes
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 0.35 V
In forward bias, the applied voltage acts opposite to the built-in potential \( V_0 \). So the barrier height falls by the applied voltage.
\( V_0=0.6\ \mathrm{V} \)
\( V=0.25\ \mathrm{V} \)
\( \begin{aligned} V_{\mathrm{eff}} &= V_0-V \\ &= 0.6-0.25 \\ &= 0.35\ \mathrm{V} \end{aligned} \)
NCERT (2026-27):
p-n junction diode under forward bias – “… As a result, the depletion layer width decreases and the barrier height is reduced … The effective barrier height under forward bias is (V0 – V ).”