PN junctions and diodes
In the diode current expression I ∝ exp(qV / nkT), when is the ideality factor n close to 2?
- AWhen minority carrier diffusion current in the neutral regions dominates
- BWhen recombination current in the depletion layer dominates
- CWhen tunneling current dominates
Show answer and explanation
Answer: B. When recombination current in the depletion layer dominates
When minority carrier diffusion current dominates, n ≈ 1, but when recombination current through defect levels in the depletion layer dominates, n approaches 2. In silicon diodes, recombination current is noticeable at low currents, and n tends to be larger there.
- A. When diffusion current dominates, n ≈ 1.
- B. Correct. Recombination current in the depletion layer gives n ≈ 2.
- C. Tunneling current does not follow the temperature dependence of the form exp(qV/nkT).