A photodiode is used to detect light because incident photons
- A. heat the junction
- B. create extra electron hole pairs, increasing the reverse current
- C. reduce the leakage current to zero
- D. change the doping of the material
Explanation
Photons with enough energy free electrons across the band gap in the depletion region, so the reverse current rises in proportion to the light intensity and gives a measurable signal. The device is therefore operated in reverse bias, the opposite of an LED. Solar cells work on the same principle but are designed to deliver power rather than a signal.