Semiconductor diode detector
From Biocrawler, the free encyclopedia.
A semiconductor diode detector is a semiconductor detector made of germanium that has found broad application during recent decades, in particular for gamma and X-ray spectrometry and as particle detectors.
In these detectors, radiation is measured by means of the number of charge carriers set free in the detector, which is arranged between two electrodes. Ionising radiation produces free electrons and holes. The number of electron-hole pairs depends on the energy transmitted by the radiation to the semiconductor. As a result, a certain number of electrons are transferred from the valence band to the conduction band, and an equivalent number of holes are created in the valence band. Under the influence of an electric field, electrons as well as holes travel to the electrodes, where they give rise to a pulse that can be measured in an outer circuit.
The energy required for production of electrons is very low compared to the energy required for production of paired ions in a gas detector; consequently, in semiconductor detectors the statistical variation of the pulse height is smaller and the energy resolution is higher. The time resolution is also very good. Compared with gas ionization detectors, the density of a Ge detector is very high and charged particles of high energy can give off their energy in a semicoductor of relatively small dimensions.
