Si/SiGe modulation-doped structures with thin buffer layers: Effect of substrate orientation

Abstract
High quality Si (strained)/Si0.7Ge0.3 (relaxed) modulation‐doped structures incorporating unusually thin (700 nm) buffer layers were grown with molecular beam epitaxy at 700 °C. By utilizing (100) substrates misoriented toward (011) by 4°, the density of threading dislocations was reduced by over an order of magnitude as compared with conventional techniques. These layers produced exceptionally high Hall mobilities of 1790 cm2/V s at 300 K and 19 000 cm2/V s at 77 K on n‐type modulation‐doped heterostructures. The effect of substrate misorientation on threading dislocation density was investigated using transmission electron microscopy and Nomarski microscopy.