AN INVESTIGATION OF 3C-SIC PHOTOCONDUCTIVE POWER SWITCHING DEVICES

Photoconductive semiconductor switches (PCSS) have unique advantages s uch as high power, high speed, negligible time jitter and long lifetim e. Silicon carbide (SIG), due to its high dielectric strength and othe r desired physical properties, is an excellent material for PCSS. Howe ver, no result has been reported on cubic silicon carbide (3C-SiC) PCS S. In this work, PCSS were fabricated on the following three types of 3C-SiC material: (i) boron doped, (ii) unintentionally doped single cr ystals, and (iii) polycrystalline. The PCSS were investigated using Ar F and XeCl excimer lasers. Practical switches with many potential appl ications were successfully fabricated. The best results were obtained from the PCSS made from polycrystalline material. The dark resistivity of the material was as high as 10(6) Omega cm. The operating breakdow n field was 250 kV cm(-1), which is the highest reported for all later al geometry PCSS and was limited by the surface flashover effect. The highest peak photocurrent density through the PCSS was greater than 10 kA cm(-2). The ratio of the off-stale resistance on the on-state resi stance, R-off/R-on, was similar to 10(5), and the lowest on-state resi stance was 45 Omega. The width of the photocurrent pulse was 15-30 ns, which was limited by the laser pulse width, indicating that the PCSS can operate in the megahertz range. The trigger gain of the polycrysta lline 3C-SiC PCSS was 4.7 and the switching efficiency was 52%. (C) 19 97 Elsevier Science S.A.