The Effects of Passivation Layers on the Response of Photoconductive Switches for Ultra-Wideband High-Power Microwave Applications

Abstract

High resistivity semiconductor materials have been used as a closing switch in a configuration for generating ultra-wideband high-power microwave radiation (Fig. 1).1 Compared to a conventional switch such as a spark-gap, the semiconductor switch has low jitter and a faster risetime and is comparatively compact in size. It also has low inductance and in the non-linear mode of operation it requires lower laser energy for switching.2 Because of its superior electrical characteristics GaAs is preferred over Si in applications where fast, repetitive switching action is required. In most cases, the material of choice is the semi-insulating GaAs with resistivity exceeding 10⁷ Ω-cm, usually grown through the compensation process.3 The compensated materials have been known to have characteristics similar to doped semiconductors where the drift-diffusion process is the dominant mode of carrier transport.4,5 The response of the device, however, is also affected by the compensation technique.⁶