What is the function of the semiconductor crystal within a semiconductor detector?

• A. Convert x-rays into electrons
• B. Convert electrons into more electrons
• C. Convert light into electrons
• D. Convert x-rays into light

Answer: (A)

The crystal in a semiconductor detector acts as the medium where incoming X-ray energy is turned into electrical charge. When an X-ray is absorbed, its energy frees electrons from their atoms, creating electron-hole pairs. The number of pairs produced is proportional to the energy deposited by the X-ray. An electric field then drifts these charges to electrodes, generating a current pulse that the detector reads. This direct conversion of X-ray energy into charge carriers is what lets the detector measure X-ray energy and intensity. It’s not about turning X-rays into light (that would be a scintillator) or about multiplying electrons; the crystal’s job is to produce and supply the charge carriers that form the signal.