PN junctions and diodes

Which is a characteristic of a PIN diode, which has a lightly doped i-layer between the p and n layers?

  1. AIt can amplify current
  2. BIts forward voltage is 0 V
  3. CThe i-layer acts as a wide depletion layer, making it suitable for high breakdown voltage and for fast, sensitive photodetectors
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Answer: C. The i-layer acts as a wide depletion layer, making it suitable for high breakdown voltage and for fast, sensitive photodetectors

In a PIN diode, the whole lightly doped i-layer acts as a depletion layer. Because the wide depletion layer can support high voltage, it is used for high-voltage diodes; and because the light-absorbing region is wide and the junction capacitance small, it is used for fast, sensitive photodetectors. It is also used as an RF switch.

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More PN junctions and diodes questions

  1. Which is a characteristic of an avalanche photodiode (APD)?
  2. In the diode equation I = Is {exp(qV / nkT) − 1}, what current flows when a large reverse voltage is applied (within the range where no breakdown occurs)?
  3. What is the purpose of a diode (flyback diode) connected in parallel with an inductive load such as a relay coil?
  4. In a forward-biased PN junction, which capacitance arises from the storage of injected minority carriers?
  5. How does the depletion width of a one-sided abrupt junction depend on the reverse bias voltage V (when V is much larger than the built-in potential)?