Relaxed SiGe buffers with thicknesses below 0.1 μm

Virtual substrates with relaxed SiGe buffers on Si substrates are needed for strain adjusted heterodevices with high cc content. We have investigated the degree of relaxation in thin (<0.1 mu m) SiGe layers grown by solid source molecular beam epitaxy (MBE) using a special low temperature growth step. Full relaxation (100%) of layers with a low temperature growth stage was achieved. X-Ray data suggest that SiGe buffers grown using this method are fully relaxed (100%), when appropriate values of Ge content, thickness and growth temperature are chosen. A typical sample with 28% Ge at total thickness of 70 nm and low temperature growth stage with 200 degrees C heater temperature is shown. TEM data indicate that the misfit dislocations are confined within the virtual substrate. Furthermore, the surface is smooth and free from strain-induced undulations and crosshatch. (C) 2000 Elsevier Science S.A. All rights reserved.