TI/PT/AU-SN METALLIZATION SCHEME FOR BONDING OF INP-BASED LASER-DIODES TO CHEMICAL-VAPOR-DEPOSITED DIAMOND SUBMOUNTS

A layered structure (consisting of Ti(100 nm)/Pt(200 nm)/Au(500 nm) and Au-Sn (2.5 mum total in multiple alternating layers)) was studied as a bonding scheme for InP-based laser diodes to chemical vapor deposited (CVD) diamond substrates. This structure provided a molten Au-Sn layer of eutectic composition (80:20 wt.%) on top of the Ti/Pt adhesion and barrier metals for about 6 s in the temperature range 300-350-degrees-C and allowed for efficient bonding of the device to the substrate. Longer heating durations allowed a reaction between the Pt and Sn to consume significant amounts of Sn from the solder, thus elevating its melting temperature and resolidifying the solder. With optimum bonding conditions, a high-quality bond of the InP-based laser diode to the CVD diamond substrate was observed, and the electrical performance of the diode was superior to that of diodes that were bonded with the standard In/BeO configurations.