Si-doped n-GaAs samples were exposed to inductively coupled plasma (ICP) NH3 discharges at different chuck temperature, pressure, source powers, and rf chuck powers to simulate the effects of ion damage and hydrogen passivation during SiH4/NH3 silicon nitride deposition for GaAs ICs fabrication. The ideality factor and reverse breakdown voltage of Schottky diodes were used to characterize the plasma damages. Both ideality factor and reverse breakdown voltage increase with increasing rf chuck power and ICP power because of the reduction of free carriers due to the lattice disorder created by the ion bombardment. A similar trend was observed with increasing deposition temperature and pressure; however, this is mainly due to the passivation of Si dopants in the GaAs donor layer by hydrogen free radicals and ion bombardment damage. The high temperature process enhances the hydrogen diffusion and high pressure produces more hydrogen free radicals and deposition bias voltage increases at both conditions.