Scanning tunneling microscopy and spectroscopy of Si‐based heterostructures

We have used cross‐sectional scanning tunneling microscopy (STM) and spectroscopy to study the electronic properties of Si (001) p‐n junctions and Si/Si1−xGex (001) strained‐layer superlattices grown by molecular‐beam epitaxy. Spectroscopic measurements on Si p‐n junctions show a clear transition between p‐ and n‐type Si, and variations in the band‐edge energies can be detected with a spatial resolution of better than 100 A. Cross‐sectional STM measurements on Si/Si1−xGex superlattices show clear topographic contrast between the Si and Si1−xGex layers, and features such as band‐edge discontinuities and band bending arising from doping can be seen in spectroscopic measurements across the superlattice structures.