An investigation of 3C-SiC photoconductive power switching devices

Abstract

Photoconductive semiconductor switches (PCSS) have unique advantages such as high power, high speed, negligible time jitter and long lifetime. Silicon carbide (SiC), due to its high dielectric strength and other desired physical properties, is an excellent material for PCSS. However, no result has been reported on cubic silicon carbide (3C-SiC) PCSS. In this work, PCSS were fabricated on the following three types of 3C-S1C material; (i) boron doped, (ii) unintentionally doped single crystals, and (iii) polycrystalline. The PCSS were investigated using ArF and XeCl excimer lasers. Practical switches with many potential applications 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 Ω cm. The operating breakdown field was 250 kV cm −1, which is the highest reported for all lateral 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-state resistance on the on-state resistance, R off/ R on, was ~ 10 5, and the lowest on-state resistance was 45 Ω. 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 polycrystalline 3C-SiC PCSS was 4.7 and the switching efficiency was 52%.