Difficulty: Easy
Correct Answer: towards positive terminal
Explanation:
Introduction / Context:Direction of carrier flow in semiconductors is a fundamental concept that underlies all device physics, from diodes to transistors. The drift motion of electrons and holes under an applied electric field determines current direction and polarity.
Given Data / Assumptions:
Concept / Approach:Electrons, being negatively charged, are attracted to the positive terminal of the applied voltage. Holes (if considered) move toward the negative terminal. This bidirectional movement results in a net current consistent with conventional direction.
Step-by-Step Solution:
Apply an electric field across the semiconductor.Electrons experience force opposite the field, i.e., drift toward the positive terminal.Therefore, free electron motion is toward the positive terminal.Verification / Alternative check:
For copper wires: electron flow is toward the positive battery terminal. The same holds in semiconductors.Why Other Options Are Wrong:
Negative terminal: would be true for holes, not electrons.Alternating 1 μs reversal: irrelevant and incorrect.Random: only true with no field.Common Pitfalls:
Confusing conventional current with electron current.Final Answer:
towards positive terminal
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