Question

a silicon (si) wafer is being fabricated by doping with boron (b) atoms. which type of semiconductor is this?
a) intrinsic
b) intrinsic and n - type
c) n - type
d) p - type

Explanation:

1. Recall the concept of semiconductor doping: Intrinsic semiconductors are pure (undoped). Doping with elements that have fewer valence electrons than the host (Si has 4 valence electrons, B has 3) creates holes (positive charge carriers), resulting in a p - type semiconductor. N - type semiconductors are doped with elements having more valence electrons (e.g., phosphorus, 5 valence electrons) to create excess electrons.
2. Analyze each option:

• Option A: Intrinsic semiconductors are undoped, but here Si is doped with B, so A is incorrect.
• Option B: Intrinsic semiconductors are undoped, and n - type has excess electrons (not from B doping), so B is incorrect.
• Option C: N - type is from doping with elements with more valence electrons (creating excess electrons), B has 3 valence electrons (less than Si's 4), so C is incorrect.
• Option D: Boron (B) has 3 valence electrons. When Si (4 valence electrons) is doped with B, B atoms form covalent bonds with Si, leaving a hole (a positive charge carrier). Semiconductors with holes as majority charge carriers are p - type. So D is correct.

Answer:

D. P - type