Influence of Thermal and Fast Neutron Irradiation on dc Electrical Performances of AlGaN/GaN Transistors
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 4.3 × 1010 neutrons.cm-2 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 (1.8 × 1012 neutrons.cm-2). 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.
Influence of Neutron Irradiation on Electron Traps Existing in GaN-Based Transistors
This paper shows the impact of low fluence neutron irradiation on AlGaN/GaN HEMTs, AlInN/GaN HEMTs and AlInN/GaN MOS-HEMTs. We have shown that the technological structure of devices and the presence of electron traps in the devices seems to play a major role on the evolution of dc electrical characteristics of irradiated GaN based transistors. After having degrading the electrical performances of AlGaN/GaN HEMTs with an electrical stress, we have shown that it is possible to improve the electrical characteristics of the stressed devices by a neutron irradiation. Moreover, we have also reported that the degradation induced by neutron irradiation is more important for the AlInN/GaN HEMTs with a gate interfacial oxide than for the AlInN/GaN HEMTs without a gate interfacial oxide.
Investigations on the rôle of organic matter in plant nutrition
1. As the result of decomposition of green manure in a swamp soil, the coarse fractions (including coarse and fine sand) of the surface layer (first 3 inches) decreased by 11·2 per cent. while the fine ones (silt+clay) increased by 9·8 per cent. in the course of 43 days. The effect was less pronounced in the manured soil maintained at 60 per cent. saturation, while no alteration was to be noticed in the case of the unmanured specimens. 2. Treatment with dilute hydrochloric acid prior to dispersion had no appreciable effect on the estimates of mechanical composition obtained in the different cases. Loss in solution was also comparatively small. 3. The silica-sesquioxide ratio increased slightly as the result of decomposition of green manure in swamp soil. The composition of the fine fractions was also altered, the total percentages of the oxides of iron, aluminium and silicon increasing from 90·5 to 99·3 in the course of 71 days. 4. The practical significance of the above and related observations has been discussed.