Compensation and doping effects in heavily helium-radiated silicon for power device applications

The formation of defects modifying the effective doping concentration of helium-radiated p(+)-n(-)-n(+) and p(+)-p(-)-n(+) silicon diodes is analyzed as a function of' the annealing temperature. After irradiation with helium at high energy levels and annealing at 220 degrees C, the probable formation of divacancy clusters increases the number of charged-acceptor states in a space-charge region. Capacitance-Voltage and Spreading-Resistance Profile measurements show that annealing at 350 degrees C results in the formation of an acceptor-like defect that deep level transient spectroscopy measurements suggest can be tentatively attributed to the V2O or V-4/V-5 Centre. Annealing at 430 degrees C results in the disappearance of acceptor-like defect. Instead, pronounced donor formation in a range close to the penetration depth of the helium ions is observed. The influence of these effects on device characteristics is discussed. (c) 2005 Elsevier Ltd. All rights reserved.