A method of fabricating a semiconductor-on-diamond composite substrate, the method comprising: (i) starting with a native semiconductor wafer comprising a native silicon carbidesubstrate on which a compound semiconductor is disposed; (ii) bonding a silicon carbide carrier substrate to the compound semiconductor; (iii) removing the native silicon carbide substrate; (iv) forming a nucleation layer over the compound semiconductor; (v) growing polycrystalline chemical vapour deposited (CVD) diamond on the nucleation layer to form a composite diamond-compound semiconductor-silicon carbide wafer, and (vi) removing the silicon carbide carrier substrate y laser lift-off to achieve a layered structure comprising the compound semiconductor bonded to the polycrystalline CVD diamond via the nucleation layer, wherein in step (ii) the silicon carbide carrier substrate is bonded to the compound semiconductor via a laser absorption material which absorbs laser light, wherein the laser has a coherence length shorter than a thickness of the silicon carbide carrier substrate.