Methods for forming a semiconductor structure are described. In an embodiment, the technique includes providing a donor wafer having a first semiconductor layer and a second semiconductor layer on the first layer and having a free surface; coimplanting two different atomic species through the free surface of the second layer to form a zone of weakness zone in the first layer; bonding the free surface of the second layer to a host wafer; and supplying energy to detach at the zone of weakness a semiconductor structure comprising the host wafer, the second layer and a portion of the first layer. Advantageously, the donor wafer includes a SiGe layer, and the co-implantation of atomic species is conducted according to implantation parameters adapted to enable a first species to form the zone of weakness in the SiGe layer, and to enable a second species to provide a concentration peak located beneath the zone of weakness in the donor wafer to thus minimize surface roughness resulting from detachment at the zone of weakness.