ON-State Characteristics of a High-Power Photoconductive Switch Fabricated From Compensated 6-H Silicon Carbide

The ON-state characteristics of a 6-H silicon carbide (SiC) photoconductive switch with vertical geometry, transverse illumination, and linear-mode operation are presented. The switch is triggered by an optical source with a photon energy that is less than the bandgap energy of SiC. Following low-power matching characteristics, the analysis of a design incorporating and layers next to the cathode shows higher hold-off voltage with an improved ON-state response mechanism. The p-layered photoconductive semiconductor switch (PCSS) can be operated at a maximum field of 875 kV/cm, whereas the n-layered PCSS, which is operating at a slightly lower field, shows higher current carrying capabilities. Higher current for the n-layer PCSS can be attributed to the nature of the region adjacent to the cathode. In the p-layered PCSS, this region inhibits an initial hole collection, thus decreasing the collected charge. In addition, a kink during the initial collection for the p-layered PCSS could influence the rise time when operating beyond 35-kV bias.

I. Introduction

Photoconductive semiconductor switches (pcsss) are fabricated from a variety of materials, including silicon (Si), gallium arsenide (GaAs), and silicon carbide (SiC). The electrical and material characteristics of each semiconductor type are different, and their applications also vary, ranging from low-impedance high-current firing sets in munitions to high-voltage high-current pulsars for ground-penetrating radar. Since the device parameters (e.g., rise-time requirement for the PCSS for high-power microwave generation may be different from those used in the firing sets) for optimum performance also depend on the specific application type, the analysis of a PCSS should be based not only on the material characteristics but also on the operational dynamics for each application. Important parameters include the blocking voltage and the pulse rise time.