6000-V gate turn-off thyristors (GTOs) with n-buffer and new anode short structure

6000-V gate-turn-off thyristors (GTOs) were developed for high-power inverters and choppers. In order to attain a high blocking voltage simultaneously with low turn-on and turn-off losses, a combination of an n-buffer layer and a cylindrical anode short structure was implemented. A 500-μm n-base width, achieved by the n-buffer structure, can decrease turn-on loss to approximately 2/3 that of a conventional anode short structure. The proposed structure is effective in sweeping away excess carriers during turn-off transient without increasing the on-state voltage very much. An average anode current of 200 A can be continuously switched at a 900-Hz operational frequency by a 33-mm-diameter device. A simultaneous diffusion process for p-base and n-buffer layers was proposed and implemented to realize the newly developed device structure