Relaxed Ge x Si 1−x layer formation with reduced dislocation density grown by ultrahigh vacuum chemical vapor deposition

A new alternative method to grow the relaxed Ge0.24Si0.76 layer with a reduced dislocation density by ultrahigh vacuum chemical vapor deposition is reported in this paper. A 1000-A Ge0.24Si0.76 layer was first grown on a Si(100) substrate. Then a 500-A Si layer and a subsequent 5000-A Ge0.24Si0.76 overlayer followed. All these three layers were grown at 600 °C. After being removed from the growth system to air, the sample was first annealed at 850 °C for 30 min, and then was investigated by cross-sectional transmission electron microscopy and Rutherford backscattering spectroscopy. It is shown that the 5000-A Ge0.24Si0.76 thick over layer is perfect, and most of the threading dislocations are located in the embedded thin Si layer and the lower 1000-A Ge0.24Si0.76 layer. The relaxation ratio of the over layer is deduced to be 0.8 from Raman spectroscopy.