Controlling voltage drops in silicon diodes by electron irradiation and thermal treatment

High-frequency limiting rectifier diodes are used in power sources for rectifying alternating current, in protective elements of radio-electronic equipment, and in switching devices. They are the basis of energy-saving devices, meeting the high requirements for power limit and performance. The main task in the manufacturing process of high-frequency diodes is to ensure the low leakage current and the optimum value of the forward voltage drop which can be compared with the contact potential difference of the p–n junction. This paper is devoted to studying the effect of radiation exposure and subsequent heat treatment on the current-voltage and capacitance characteristics of high-frequency silicon diodes.The authors studied p+–p–n–n+ diodes made of n-type KEF-4 (КЭФ-4) silicon wafers with an initial thickness of 235 μm. Radiation processing was performed using an ELU-6 (ЭЛУ-6) linear electron accelerator. The integral flux of "fast" electrons ranged from 1,0·1015 to 2,6·1017 cm–2, energy was 1.5 MeV, density was 1,7·1011 — 5,5·1013 cm–2·s–1. Heat treatment was performed for 5 hours at a temperature of 90°C in a special chamber. The studies have shown that heat treatment lead to a shift of the forward current-voltage characteristic to a region of lower voltages (i.e., a given current can be reached at a lower voltage); at low current values, however, the voltage drop may increase after heat treatment. Reverse current decreased fivefold, resulting in a decrease in power output. At the same time, the temporal characteristics of the diode could also be improved by reducing the capacitance (to one order of magnitude)

Estudo da diversidade de Sardinella brasiliensis (Steindachner, 1879), na área entre Macaé (22º23'S) e Ilha de Santa Catarina (27º35'S): 1. Crescimento de dimensões corporais

<abstract language="eng">The growth of body proportions of Sardinella brasiliensis was not homogeneous in the study area, between Macaé (RJ) and Santa Catarina Island (SC); the growth rates (K) of the von Bertalanffy growth curve were greater than growth rates for another áreas. In this area the biomass estimates for pelagic fish is poor, and near Cabo Frio occurs an upwelling zone. These facts permit the sardines to attain large lengths in this area. Between Rio de Janeiro and Florianópolis the growth rates were lower than in the northern part and Paranaguá Bay. On the other hand the biomass estimates for pelagic fish in Rio de Janeiro-Florianópolis region was very high, and in this zone the population density is high and the growth rates are small. Paranaguá Bay is a particular region because of its geographical and oceanographic conditons; this is a shelter region with different features and the sardines living there attain small length. In this area the growth rates are intermediary among growth rates for fishes from Macaé-Cabo Frio and Rio de Janeiro-Florianópolis regions. Therefore, the growth rates for sardines in southeast Brazilian proves to be dependent of the population density, food and oceanographic conditions