GROWTH AND CHARACTERIZATION OF HIGH-Ge CONTENT SiGe VIRTUAL SUBSTRATES

摘要

Si_(1-x)Ge_x virtual substrates with relaxed graded buffers grown in industrial LPCVD reactors on 150 mm and 200 mm diameter wafers are presented with compositions up to x = 1. By taking advantage of an intermediate planarization step, we are able to achieve dislocation glide limited relaxation throughout the growth of the entire graded buffer layer. This resulted in a threading dislocation density of 2 x 10~5 cm~(-2) that was independent of the ultimate composition for substrates with x > 0.4. Ge-on-Si virtual substrates exhibited an rms surface roughness of 3.27 nm for a 20 μm x 20 μm area and a very low density of epitaxial defects. These substrates were used to fabricate both Ⅲ-Ⅴ solar cells and visible LEDs. The preliminary results of the devices showed no degradation in device performance from the graded buffer layer, demonstrating the commercial readiness of the SiGe virtual substrates.