Low-resistivity GaAs/Si metal-mediated wafer bonding has been investigated for silicon photonics applications. Ag thin-film bonding agent was found to significantly reduce interfacial resistivity relative to the previous bonding mediated by Au-based alloy. Lowering of the interfacial resistivity was found to saturate at 1–2 h of bonding time. A bonding temperature around 300 °C was found optimal to balance the trade-off between elemental interdiffusion and oxidation. On the basis of the bonding investigation, 1.3 μm InAs/GaAs ridge-type quantum dot lasers on Si substrates with Au-free GaAs/Si heterointerfaces have been fabricated. The laser device exhibited a significantly lower device series resistivity and threshold current density than the previous Au-mediated-bonded and direct-grown lasers.