The invention relates to a method for fabricating a composite structure having heat dissipation properties greater than a bulk single crystal silicon structure having the same dimensions. The structure includes a support substrate, a top layer and an oxide layer between the support substrate and the top layer. The method includes providing a top layer made of a crystalline material, providing a support substrate of a polycrystalline material having heat dissipation properties greater than that of a bulk single crystal silicon substrate of the same dimensions; providing an oxide layer on at least one of the top layer or the support substrate; bonding the top layer and support substrate together to obtain a composite structure having the top layer, the support substrate and the oxide layer located at a bonding interface between the top layer and support substrate, and heat treating the composite structure in a non-oxidizing atmosphere at a predetermined temperature and for a predetermined duration to dissolve at least part of the oxide layer and increase the heat dissipation properties of the composite structure compared to the composite structure prior to the heat treating.