Metallic wafer bonding for the fabrication of long-wavelength vertical-cavity surface-emitting lasers

摘要

[[abstract]]A novel metallic bonding method using AuGeNiCr as the bonding medium was developed for the fabrication of long-wavelength vertical-cavity surface-emitting lasers (VCSELs). The metallic bonding process can be performed at a low temperature of 320 °C within 1 h and it does not require chemical-mechanical polishing or etching treatments on the bonding surfaces. As determined by atomic force microscopy, the process can tolerate a surface roughness of ∼10 nm on the surface of bonding samples. Cross-sectional transmission electron microscopy shows that the bonding interface is smooth and damage-free. Using this bonding technique, a 1.55 μm GaInAsP/InP VCSEL structure with Al-oxide/Si distributed Bragg reflectors was demonstrated on a Si substrate. No degradation was found on the bonded VCSEL structure after annealing at 420 °C. The reflectivity and resonance measured from the bonded VCSEL cavity confirmed the high optical quality provided by this bonding process for device fabrication.