There is disclosed a method of forming layers of either GaAs or germanium materials such as SiGe. The germanium material, for example, may be epitaxially grown on a GaAs surface. Layer transfer is used to transfer the germanium material, along with some residual GaAs, to a receiver substrate. The residual GaAs may be then removed by selective etching, with the boundary between the GaAs and the germanium material providing an etch stop.