Plasma‐induced etch damage often degrades the electrical and optical performance of III–V high‐density integrated circuits and photonic devices. We have investigated the etch‐induced damage of electron cyclotron resonance (ECR) generated plasmas on the electrical performance of mesa‐isolated GaAspn‐junction diodes. Cl2/Ar, BCl3/Ar, Cl2/BCl3/Ar, and SiCl4/Ar ECR plasmas at ion energies ranging from 10 to 200 eV were studied. Diodes fabricated under low dc‐bias (≤100 V) etch conditions yielded low reverse‐bias currents which were comparable to wet‐chemical‐etched devices. As the dc bias was increased, the diodes showed significantly higher reverse‐bias currents indicating plasma‐induced sidewall damage of thepn‐junction. Variations in diode reverse‐bias leakage currents are reported as a function of plasma parameters and chemistries.