PROFILING GE ISLANDS IN SI BY LARGE-ANGLE CONVERGENT-BEAM ELECTRON-DIFFRACTION

Large angle convergent beam electron diffraction (LACBED) is used to p rofile thin buried Ge layers in Si consisting of islands 100-200 nm ac ross on top of a wetting layer. These studies, tarried out in a FEGTEM using plan-view samples, examine two-beam rocking curves for reflecti ons from planes inclined to the growth direction. A simple measurement of the rocking curve asymmetry is used to profile the net outward dis placement across the Ge layer due to lattice mismatch from which the t otal Ge content is derived. By combining these results with observatio ns on cross-sectional samples giving the Ge layer thickness, the avera ge Ge concentration is derived. The application of the LACBED techniqu e to the profiling of semiconductor strained layers in general is disc ussed. It is shown that a single atomic layer of Ge in Si should be de tectable.