The optical characteristics of directly wafer-bonded InP-GaAs heterojunctions have been investigated. By designing the bonding interface at standing-wave antinode. its influence on optical performances of bonded structures is magnified, which facilitates experimental detection using optical methods. Wavelength blueshift and reflectivity falling at the resonance mode were observed in water-bonded InP-GaAs heterostructures. Numerical analysis suggests that two effects involving thickness change of interfacial bonding layers and extra optical loss introduced by bonded junctions are responsible for the experimental observations. and these effects can be attenuated by lowering anneal temperatures and incorporating an InP/InGaAsP superlattice into the surface of InP-based materials. The results are useful for designing effective optical characteristics of wafer-bonded device Structures. (c) 2009 The Electrochemical Society. [DOI: 10.1149/1.3071521] All rights reserved.