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 °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 °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 V4/V5 centre. Annealing at 430 °C results in the disappearance of the 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.