Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 54 of 494
What is the approximate potential barrier across the depletion region of a germanium \( \text{P-N} \) junction at room temperature?
A
\( 0.3\text{ V} \)
B
\( 0.7\text{ V} \)
C
\( 0.9\text{ V} \)
D
\( 1.2\text{ V} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( 0.3\text{ V} \)
Concept:

Germanium has a smaller energy bandgap than silicon, resulting in a lower built-in electric potential barrier across its depletion layer.

Formula:

$$V_B \approx 0.3\text{ V (for Germanium at } 300\text{ K)}$$

Solution:

  • At room temperature (\( 300\text{ K} \)), the internal diffusion of carriers creates an equilibrium barrier potential of \( 0.3\text{ V} \) across a germanium \( \text{P-N} \) junction.


Why other options are incorrect:

  • Option B: \( 0.7\text{ V} \) is the potential barrier for silicon.


  • Option C: \( 0.9\text{ V} \) is significantly higher than the standard germanium barrier.


  • Option D: \( 1.2\text{ V} \) is typical for wide-bandgap semiconductors such as Gallium Arsenide.

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.

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