NEW BUFFER CONCEPT INHERENT TO PULSED-LASER INDUCED EPITAXY

We demonstrate the growth Of a 250 nm-thick graded buffer based on Si1 -x-yGexCy. This buffer, with 0<x<0.25 and 0<y<0.004, looks entirely fr ee from threading dislocation. Its original microstructural arrangemen t is inherent to the growth method: pulsed-laser induced epitaxy, Afte r epitaxy, small amorphous precipitates are buried at the former amorp hous/crystalline interface. They behave like buffers capable of storin g 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 substra te. This indicates that pulsed laser induced epitaxy is a promising me thod for new buffer concepts with low threading dislocation densities. (C) 1998 American Institute of Physics.