Which material is responsible for generating the initial signal in a semiconductor detector when radiation interacts with it?

• A. Photoconductor crystal
• B. Photocathode
• C. Amplifier
• D. Metal housing

Answer: (A)

In a semiconductor detector, the first signal comes from the detector material itself. When radiation interacts with the photoconductor crystal, it deposits energy that creates electron–hole pairs within the crystal. These charge carriers are pulled by an applied electric field, producing a current pulse that forms the initial electronic signal read out by the electronics. The photoconductor is the active material that directly converts the radiation interaction into charge, whereas a photocathode is used in other devices to convert light into electrons, an amplifier merely boosts the signal, and the metal housing is just a container.