High Resolution Channeling Contrast Microscopy and Channeling Analysis of SiGe Quantum Well Structures

High resolution channeling contrast microscopy (CCM) and channeling measurements were carried out to characterize SiGe quantum well structures on micron thick graded layers (i.e. virtual substrates). The virtual substrates were grown by gas source molecular beam epitaxy at a pressure of 10 5 mbar and low pressure chemical vapor deposition at 10 2 mbar on boron doped Si(0 0 1) substrates respectively. A homoepitaxial silicon buffer layer was grown prior to the deposition. The nominal structure is a 20 nm Si0:75Ge0:25 layer at the surface, followed by 10 nm pure Si, 500 nm Si0:75Ge0:25 and a 1000 nm thick graded SiGe (0–26%) layer. RBS was used to measure the depth profiles, and angular scans around the (1 0 0) axis were carried out to assess crystal and interface quality. CCM was used to acquire depth resolved images of micron-sized lateral inhomogenities (‘cross-hatch’) present on both samples. 2002 Elsevier Science B.V. All rights reserved. PACS: 82.80.Yc; 61.85.þp; 68.55.Jk