Heterogeneous InP-on-Insulator Wafer via Surface Activated Room-Temperature Quasi-direct Bonding

In this study, we investigated the room-temperature wafer bonding of indium phosphide (InP) and thermally oxidized Si (SiO 2 ). The bond strength of InP/SiO 2 wafers via surface-activated direct bonding and room-temperature quasi-direct bonding using an activated Si atomic layer were compared, and the bonding using an activated Si atomic layer resulted in a tenfold increase in bond strength. The surface morphology and atomic structure of the bonding interface were characterized to confirm that the bond strength was enhanced because the InP surface with an activated atomic Si layer maintained low roughness, and a strong direct bond between the activated Si atoms was obtained simultaneously. Subsequently, the state of In and P diffusion at the bonding interface was verified. The observation of the debonded surfaces showed that although In and P diffuses into the activated Si atom layer, the amount is negligible, and the bonding interface consists almost entirely of strong Si-Si bonds. Using this room temperature quasi-direct bonding method, the heterogenous InP-on-insulator wafer bonded at room temperature is suitable for fabricating optical and electronics devices and could be integrated with other exciting material platforms. • The fabrication of heterogeneous InP-on-insulator (InPOI) wafers was demonstrated using a surface-activated, room-temperature quasi-direct wafer bonding method. • The tensile strength of the bonded InPOI wafers at room temperature exceeded 29 MPa, indicating that the InP/SiO 2 bonding interface achieves sufficient bond strength. • Void-free atomic contact formation at the InP/SiO 2 bonding interface was confirmed. • Detailed investigations of the bonding interface and debonded surfaces clarified the formation of a strong InP/SiO 2 bonding interface.