Image sensors and optical devices

Why is it difficult to increase the near-infrared sensitivity of silicon image sensors?

  1. ABecause silicon absorbs near-infrared light weakly, so it penetrates deep into the silicon
  2. BBecause near-infrared light does not pass through lenses
  3. CBecause near-infrared light does not generate electrons
Show answer and explanation

Answer: A. Because silicon absorbs near-infrared light weakly, so it penetrates deep into the silicon

Silicon absorbs longer wavelengths more weakly, and near-infrared light penetrates deep below the photodiode. A thin photodiode cannot absorb enough of it, so sensitivity is low. Structures that trap light near the surface and thicker absorption layers are used to address this.

Practice this topic Back to topic

More Image sensors and optical devices questions

  1. What is the purpose of correlated double sampling (CDS) used in CMOS image sensor readout?
  2. Which is a characteristic of an OLED (organic EL) display?
  3. In the typical four-transistor pixel of a CMOS image sensor, which transistor moves the charge from the photodiode to the floating diffusion?
  4. What is the noise called that appears the same way at the same positions every time because of pixel-to-pixel variation in characteristics?
  5. How does the size of shot noise, caused by statistical fluctuation in the number of photons, relate to the number of signal electrons N?