radiation detector in which a semiconductor material such as a silicon or germanium crystal constitutes the detecting medium. One such device consists of a junction (p-n junction) across which a pulse of current develops when a particle of ionizing radiation traverses it. In a different device, the absorption of ionizing radiation generates pairs of charge carriers (electrons and electron-deficient sites called holes (hole)) in a block of semiconducting material; the migration of these carriers under the influence of a voltage maintained between the opposite faces of the block constitutes a pulse of current. The pulses created in this way are amplified, recorded, and analyzed to determine the energy, number, or identity of the incident-charged particles. The sensitivity of these detectors is increased by operating them at low temperatures—commonly that of liquid nitrogen, −164 °C (−263 °F)—which suppresses the random formation of charge carriers by thermal vibration.