Development of “Stitch” Super-GTOs for pulsed power

Newly designed, high-power silicon gate turn-off thyristors are being evaluated to satisfy the U. S. Army´s need for compact, lightweight pulse switches. Following the successful demonstration of a 3.5 cm² silicon Super-GTO, Silicon Power Corporation re-designed the emitter layout and increased the device footprint to create a switch optimized for use in high-current, wide-pulse applications. The 7 cm² silicon “Stitch” Super-GTO was developed to block 7 kV. The 2x increase in die size actually results in a 2.5x increase in active area because a portion of chip area that was previously taken up by perimeter high voltage termination is now used for conduction. The Super-GTOs were evaluated at the Army Research Laboratory in a low-inductance pulse-forming network. Pulse current was successfully stepped up as high as 35 kA, corresponding to a current density of 5 kA/cm² over the chip´s footprint. This corresponds to 7 kA/cm² over the active emitter area, when the edge termination is excluded. Compared to Silicon Power´s original device, the new larger component conducted 40% higher current density. The 35 kA current pulse had a width of 125 μs and an I²t of 9.2 ×10⁴ A²s. The 10-90% rise of the current pulse was 2.4 kA/μs, and the maximum on-state forward conduction drop was 28 V. Given good processing and packaging yields, this larger Stitch Super-GTO can greatly reduce the size of high current pulse switches.