Proton, neutron and electron-induced displacement damage in germanium

Displacement damage factors for several types of germanium bipolar transistors have been measured for 15- and 30-MeV electrons, 22-, 40-, and 63-MeV protons, and fission neutrons. Each device was irradiated with both neutrons and either electrons or protons so that damage factor ratios could be determined. In this way dependence on resistivity, injection level, and device variability could be removed. The damage factor ratios were found to be directly proportional to the calculated nonionizing energy loss for electrons and protons over approximately two orders of magnitude. This means that the damage factors are directly proportional to the number of defects initially formed, whether as point defects or in cascades, and that the stable defects act independently so far as transistor gain is concerned. No evidence of cluster-space-charge effects was found. The implication of the results for a determination of a 1-MeV (GE) neutron damage equivalent fluence is discussed