Concept:Acceptor impurity atoms require a small amount of energy to accept an electron from the valence band, creating a discrete energy level just above the valence band edge.
Formula:$$\Delta E_a = E_a - E_v \approx 0.045\text{ eV} \text{ to } 0.057\text{ eV} \quad (\text{for Boron in Silicon})$$
Solution:- Trivalent dopant atoms introduce vacant electron states near the valence band.
- In the band diagram, the acceptor energy level (\( E_a \)) sits inside the forbidden gap, roughly \( 0.05\text{ eV} \) above the valence band edge \( E_v \).
- Thermal energy at room temperature readily excites electrons from the valence band into these acceptor states, creating holes in the valence band.
Why other options are incorrect:- Option A: States near the conduction band correspond to donor impurities in N-type material.
- Option C: Mid-gap states are associated with deep traps, not shallow dopants like boron.
- Option D: Acceptor levels lie near the valence band edge, not in the conduction band.
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.