Passivation of InP surfaces have been achieved using low-power (∼50 W) electron cyclotron resonance (ECR) hydrogen plasmas and SiNx overlayers. The nitride layers are deposited at room temperature using a ECR plasma-enhanced chemical vapor deposition technique. In situ, real-time photoluminescence measurement is used to monitor the InP surface during H plasma treatment. It is observed that a 30 s “flash” ECR H plasma treatment of InP surface helps fabrication of passivated SiNx–InP interfaces with a low density of interfacial defects. © 1998 American Institute of Physics.