The structural transformations which were produced in strain-relaxed low dislocation-density Si0.6Ge0.4 films by As+ implantation and rapid thermal annealing were studied by means of transmission electron microscopy and X-ray microanalysis. The type of residual defect was found to depend strongly upon the annealing temperature. Only perfect dislocation loops were observed in implanted layers after annealing at 800C. Annealing at 900C resulted in the complete removal of irradiation damage, together with the formation of GeAs precipitates of monoclinic structure and spherical shape. The results showed that the behavior of As in Si-Ge alloys during heat treatment was markedly different to that in Si. In particular, the precipitation of As atoms in the present material occurred at an As concentration of 9 x 1020/cm3. This value was at least an order of magnitude lower than the critical As concentration for As precipitation in Si.

V.S.Tishkov, P.I.Gaiduk, S.J.Shiryaev, A.N.Larsen: Applied Physics Letters, 1996, 68[5], 655-7