We obtained new insight into ESD-degradation mechanisms on GaAs FET devices. It is shown that the commonly used gold-based metallizations (e.g. AuGeNi) degrade at low temperatures by interdiffusion with the GaAs substrate under ESD stress. Special contacts developed in our laboratory show remarkable stability against ESD stress with the human body model (HBM 1000V, MIL-883). All devices were analyzed with REM and EDAX. Based on investigations to find the thresholds of the ESD voltage inducing degradations to GaAs-Schottky and ohmic contacts, we have developed and fabricated new fast switching structures. The switching structures are based on electron field emission with the aim to construct protection circuits to prevent the microwave devices and circuits from degradation caused by electrostatic discharge (ESD). We examined their overall characteristics regarding GaAs devices.