Concept:Germanium has a smaller energy band gap (\( E_g \approx 0.7\text{ eV} \)) than silicon (\( E_g \approx 1.1\text{ eV} \)), resulting in a lower built-in barrier potential.
Formula:$$V_{0,\text{Ge}} \approx 0.3\text{ V} \quad (\text{at } 300\text{ K})$$
Solution:- The built-in potential barrier across a Ge junction at room temperature is approximately \( 0.3\text{ V} \).
- Consequently, a germanium diode turns ON at a lower forward voltage (\( \approx 0.3\text{ V} \)) than a silicon diode (\( \approx 0.7\text{ V} \)).
Why other options are incorrect:- Option A: 0.7 V is the barrier potential for Silicon.
- Option C: 1.1 V represents the bandgap energy of Silicon in eV, not the barrier potential of Germanium.
- Option D: A finite barrier potential exists at equilibrium in all PN junctions; it is never 0.0 V.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.