New buffer concept inherent to pulsed laser induced epitaxy

We demonstrate the growth of a 250 nm-thick graded buffer based on Si_1-x-yGe_xC_y. This buffer, with 0<x<0.25 and 0<y<0.004, looks entirely free from threading dislocation. Its original microstructural arrangement is inherent to the growth method: pulsed-laser induced epitaxy. After epitaxy, small amorphous precipitates are buried at the former amorphous/crystalline interface. They behave like buffers capable of storing elastic energy. With proper annealing parameters, no dislocation is seen by transmission electron microscopy. This result is obtained when the laser fluence is sufficient to melt the layer down to the substrate. This indicates that pulsed laser induced epitaxy is a promising method for new buffer concepts with low threading dislocation densities.