Patent ID: 7452792

Claim:
A method of forming a layer of elastically unstrained crystalline material, which method comprises: providing first and second crystalline layers of different composition adjacent each other, wherein one layer is elastically strained under tension and the other layer is elastically strained in compression; providing a step of diffusion of at least one element between the layers so that the compositional differences between the respective compositions of the two layers reduces progressively until they are substantially the same, the two layers then forming just a single final relaxed layer of crystalline material having, in aggregate, a uniform composition, and wherein the respective compositions, thicknesses, and degrees of strain of the two layers are initially selected so that, after diffusion, the material then constituting the final layer no longer, in the aggregate, exhibits elastic strain; wherein one layer is formed from Si 1-x Ge x , the other layer is formed from Si 1-y Ge y and the final relaxed layer is formed from Si 1-z Ge z , with x and y respectively being in the range of 0 to 1 inclusive and z being above 0 but less than 1.