Thermal Neutron Damage in Bipolar PNP Transistors.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
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An experimental test was made of the hypothesis that the source of thermal neutron damage in bipolar PNP transistors is the result of thermal neutron captures by the Boron 10 present in the emitter region of the transistors. Transistors were specifically made using three different ratios of Boron 10 to Boron 11 as the emitter dopant material, and in four different geometries. Forty-two of these specially made transistors were exposed to thermal neutron fluences as high as approximately 5 x 10 to the 15th power neutrons per square centimeter. In each case the damage observed corresponded to the fraction of Boron 10 to total boron used as the emitter dopant material, thus confirming the hypothesized damage mechanism. The dependence of the collector current, thermal neutron fluence, and emitter-base geometry on the observed gain degradation also indicated that bulk damage is responsible for thermal neutron damage in PNP transistors. Some devices were also irradiated in a fast neutron environment. Fast neutrons were found to be approximately one hundred times more effective than thermal neutrons in producing damage in the devices that use a naturally occurring ratio of Boron 10 to Boron 11 in the emitter. Author
- Electrical and Electronic Equipment
- Nuclear Radiation Shielding, Protection and Safety