Influence of cooling rate on the dislocations and related luminescence in LPE SiGe layers grown on Si (100) substrates

Abstract

Thick relaxed SiGe layers have been grown using the liquid phase epitaxy (LPE) technique. The Ge contents in the layers varied from 3.4 to 12.9 at.%. The thickness of the layers was approximately 25–30 μm. The layers grown at low cooling rates and with low Ge contents had low threading dislocation densities. Etch pit density of the layers increased from 2×10 4 to 8×10 5 cm −2 with increasing cooling rates from 20 K/h to 500 K/h during the LPE process. Etch pit density of the SiGe layers increased from 8×10 4 to 7×10 6 cm −2 as the Ge content in the layers increased from 3.4 to 12.9 at.%. The good quality of the layers grown at low cooling rates has been demonstrated by the strong no-phonon and TO phonon near band gap luminescence of the layers. Strong increase in the intensities of D and T bands was observed in the layers having high Ge contents and grown at high cooling rates. The increase in the intensity of the dislocation related D and T band luminescence in the layers has been related to the increase in the dislocation density of the layers.