Doping compensation for increased robustness of fast recovery silicon diodes
Abstract High-power diodes with the radiation enhanced diffusion (RED) of Pd are shown to have much higher ruggedness during the reverse recovery compared to that of the Pt. Anode doping profiles measured by spreading resistance technique after a 10 MeV He implantation with subsequent annealing between 500 and 800 °C reveal different compensation effects between the Pd and Pt. The in-diffusing Pd converts the n-type background doping concentration of ND = 3 × 1013 cm−3 in the position of radiation defects to that of a p-type with about one order higher concentration. The created low-doped p-layer significantly increases ruggedness of diodes during reverse recovery. In the diodes with the Pt layer, only a modest compensation is observed, a conversion to a p-type layer is missing and robustness is much lower. The DLTS spectra for the Pt and Pd devices show a similar electronic structure and introduction rates of defects at 700 °C, while they differ significantly at 600 and 650 °C both for the majority and minority carriers. It is preliminary suggested that the strong compensation effect after the RED of Pd is caused by a high introduction rate of an acceptor deep level at the lower half of the silicon bandgap.