Si/SiGe quantum wells grown on vicinal Si(001) substrates: Morphology, dislocation dynamics, and transport properties

Compositionally graded, strain relaxed Si_0.72Ge_0.28 buffers were grown on vicinal Si(001) substrates by gas source molecular beam epitaxy. Misfit dislocations are shown to run along intersections of the 111 glide planes with the (11n) interface. X-ray diffraction studies demonstrate a relative tilt of the epilayer to the substrate in a direction which depends on the interplay between substrate orientation related preferential dislocation nucleation rates and surface contamination induced heterogeneous nucleation. Atomic force microscopy (AFM) images reveal an anisotropy in surface roughness on the μm scale related to reduced growth rates on vicinal surfaces. Transport properties at 0.4 K in two dimensional electron gases grown on these relaxed SiGe buffers show anisotropic scattering times similar to interface roughness scattering which can be correlated to terrace configurations in the nm range determined by AFM.