GaN ( 1 1 ¯ 00 ) cleavage surfaces were investigated by cross-sectional scanning tunneling microscopy and spectroscopy. It is found that both the N and Ga derived intrinsic dangling bond surface states are outside of the fundamental band gap. Their band edges are both located at the Γ¯ point of the surface Brillouin zone. The observed Fermi level pinning at 1.0 eV below the conduction band edge is attributed to the high step and defect density at the surface but not to intrinsic surface states.
Ring-shaped GaSb/GaAs quantum dots, grown by molecular beam epitaxy, were studied using cross-sectional scanning tunneling microscopy. These quantum rings have an outer shape of a truncated pyramid with baselengths around 15 nm and heights of about 2 nm but are characterized by a clear central opening extending over about 40% of the outer baselength. They form spontaneously during the growth and subsequent continuous capping of GaSb/GaAs quantum dots due to the large strain and substantial As-for-Sb exchange reactions leading to strong Sb segregation.
GaSb quantum rings in GaAs were studied by cross-sectional scanning tunneling microscopy. The quantum rings have an outer shape of a truncated pyramid with typical lateral extensions between 10 and 30nm and heights between 1 and 3nm, depending on the molecular beam epitaxy growth conditions. A clear central opening of varying diameter and more or less conical shape, filled with GaAs, is characteristic for the GaSb rings. The self-organized formation of quantum rings during the growth and subsequent fast overgrowth of GaSb quantum dots is attributed to a combination of large strain with strong Sb segregation. The latter is enabled by extensive group-V atomic exchange reactions at the GaSb∕GaAs interfaces, which are quantitatively evaluated from the atomically resolved microscopy data.
This overview, based on earlier published papers, concerns the growth and some properties of single and polycrystalline cubic silicon carbide (3C‐SiC) prepared by thermal decomposition of methyl trichlorosilane in hydrogen on resistively heated graphite substrates in a temperature range of 1500 to 2100 K. The morphology of faceted crystals and their specific twin structure, as well as the effects of crystallographic polarity of the 3C‐SiC structure (sphalerite type) on impurity segregation and etching are considered in some detail.
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