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

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 degreesC 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 similar to10 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 mum 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 degreesC. The reflectivity and resonance measured from the bonded VCSEL cavity confirmed the high optical quality provided by this bonding process for device fabrication. (C) 2002 American Institute of Physics.