Low Temperature VECSEL-to-Diamond Heterogeneous Integration with Ag-In Spinodal Nanostructured Layer

Abstract

Low temperature heterogeneous integration with diamond is the key technology in pushing upwards the high-power limit of a vertically-external-cavity surface-emitting laser (VECSEL). This work successfully accomplished a functional high-power VECSEL-to-diamond device with a modified Ag-In transient liquid phase (TLP) bonding technology. The post-bonding quality of VECSEL epitaxial membrane was thoroughly examined with scanning electron microscopy (SEM), focus ion beam (FIB) and high resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Owing to the low-temperature process, thermal-activated diffusion and thermo-mechanical stress have been suppressed to the minimal level within the epitaxial layers while optimizing the heat-spreading capability of the diamond. Interestingly, with experimental and thermodynamic evidences, a distinct nanostructure from spinodal decomposition has been discovered in the Ag-In bonding layer for the first time, whose structural feature is beneficial to the reliability of a VECSEL-to-diamond device. Conceptually, this work opens a new bonding technology category, i.e., Ag-In spinodal bonding.