The fabrication of a wafer-scale dislocation-free, fully relaxed single crystalline template for epitaxial growth is demonstrated. Transferring biaxially strained In(x)Ga(1-x)As ultrathin films from InP substrates to a handle support results in full strain relaxation and the In(x)Ga(1-x)As unit cell assumes its bulk value. Our realization demonstrates the ability to control the lattice parameter and energy band structure of single layer crystalline compound semiconductors in an unprecedented way.