3.2.6.2 PIN diode detectors

Thermo-electrical cooling opened the possibility to store and operate solid state detectors at relatively high temperatures, eliminating the need for liquid nitrogen cooling. Additionally, the detectors can be mounted in very compact designs, thus making them useful for light-weight portable instruments.

A PIN diode detector operates under high-level injection: The intrinsic "i" region is flooded with charge carriers from the "p" and "n" regions. When the diode is forward biased, the injected carrier concentration is typically several orders of magnitude higher than the intrinsic level carrier concentration, and the electric field extends deeply (almost the entire length) into the region.