Ag-metal bonding conditions for low-loss double-metal waveguide for terahertz quantum cascade laser

The Ag-metal bonding conditions for the double-metal waveguide (DMW) of terahertz quantum cascade lasers (THz-QCLs) were investigated. GaAs wafers were bonded together with Ag-metal layers by applying high-pressure and heat. We achieved successful Ag bonding at 400degC with an applied pressure of 38.5 kg/cm
²
for 30 min in N
₂
ambient. A thin Ti adhesion layer was inserted between Ag and GaAs. The Ti layer (thickness ges10 nm) was, in addition, found to act as a barrier preventing Ag diffusion into GaAs at temperatures below 400degC.