Abstract: A solid state fast-neutron spectrometer/dosimeter and a detector therefor are presented. The detector comprises a substrate of organic semiconductor material and a coating of a nuclearly inert metal with a Fermi level greater than that of the substrate, the metal being applied so as to form a rectifying barrier with the substrate. Multi-substrate detector embodiments provide greater sensitivity and precision in an incorporating spectrometer/dosimeter. A pulse height analyzer is used to obtain a pulse height distribution from the output of the detector. The pulse height distribution may be converted by means of a microcomputer to yield a neutron energy distribution for spectrometer applications, or a total neutron energy reading for dosimeter applications.