Abstract: In a method for bonding a silicon substrate to a III-V material substrate, a silicon substrate is contacted together with a III-V material substrate and the contacted substrates are annealed at a first temperature that is above ambient temperature, e.g., at a temperature of between about 150° C. and about 350° C. The silicon substrate is then thinned. This bonding process enables the fabrication of thick, strain-sensitive and defect-sensitive optoelectronic devices on the optimum substrate for such, namely, a thick III-V material substrate, while enabling the fabrication of silicon electronic devices in a thin silicon layer, resulting from the thinned Si substrate, that is sufficient for such fabrication but which has been thinned to eliminate thermally-induced stress in both the Si and III-V materials. The III-V material substrate thickness thereby provides the physical strength of the composite substrate structure, while the thinned silicon substrate minimizes stress in the composite structure.