Gate turn-off thyristors with near perfect technology

Turn-off current of conventional high power GTO-thyristors is limited by local differences in doping and/or carrier lifetime. In order to avoid inhomogeneities inherent in conventional deposition techniques, a novel technological sequence, using irradiated particles, is considered: a) neutron transmutation doping of starting material b) ion implantation of doping layers c) electron irradiation for carrier lifetime control Using an automatic computer-controlled prober, local variations of p-base surface concentration are evaluated by a simple but extremely accurate method (σ=0.16%). Deviations of 5+6% from average for a conventional B-diffused element are reduced by more than a factor 3 by ion implantation. Similarly, the differences in forward voltage drop due to Au diffusion are reduced by more than a factor 5 using electron irradiation. Virtually all electrical differences between GTO segments are shown to disappear with the application of these technologies.