InGaAsP/InP strained-layer quantum well ridge waveguide lasers of 1.3 mu m have been successfully bonded to a GaAs substrate by surface activated wafer direct bonding at room temperature. In this method, the surfaces of two wafers are activated by Ar fast atom beam irradiation and joined under high vacuum conditions. In most cases a high bonding strength was attained. No microcracks and voids were observed by transmission electron microscopy at the bonded interface. A low threshold current density of about 500 A/cm(2) has been achieved. This technique is very promising to realize monolithic integration of optoelectronic integrated circuits for optical communication and interconnections. (C) 1998 American Institute of Physics.