The influence of thermal neutron irradiation and fast neutron irradiation on the electrical properties of AlGaN/GaN HEMTs is investigated. An increase in the drain current and a decrease in the access resistances are observed when devices are irradiated with a thermalized neutrons fluence of while no evolution is observed with the same fluence of fast neutrons. However, the same phenomenon is observed when the fast neutron fluence is higher . AlGaN/GaN heterojunctions are analyzed by gamma spectroscopy after thermalized or fast neutron irradiations to understand the physical mechanisms induced by irradiations. In fact, we have shown that the improvement of electrical properties of devices after thermal neutrons irradiation is linked to a Ga-Ge transmutation effect. Moreover, the evolution of the drain current and access resistance when the AlGaN/GaN heterojunctions are irradiated by fast neutrons can be induced by N vacancies creation and/or a change of the strain state of the layers and/or Ga-Ge transmutation effect.
An assesment method for tritium contamination surface by using portable liquid scintillation system on survey smears.An assessment method for tritium surface contamination by liquid scintillation on survey smears is proposed, which employs a special device, the Triathler TM , till now used only by highly specialized laboratories. Based on the parameters involved in the measurements, an accurate and new procedure is developed which reduce to few minutes an activity measurement within the prescribed conditions of thresholds set by the radioactive materials transports. Though centered on transport contamination, this work may activate a more extended reflection about contamination itself in different fields of human activity.
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