Electron microscopy of ultra-thin buried layers in InP and InGaAs

The large-angle convergent-beam electron diffraction (LACBED) technique has been used to measure layer thicknesses and strain of ultra-thin arsenic and phosphorus-rich layers produced by temporary arsine and phosphine purges in the metal-organic vapour phase epitaxy growth of InP and InGaAs. The paper describes how the technique, previously used to investigate single quantum wells of thickness between 8 and 30 angstrom, has been extended to layers of thicknesses of one to two monolayers. It is shown that LACBED patterns can be recorded under conditions in which only a small constant inelastic background and elastic scattering need be considered and can be analysed in detail using a kinematical approach. By combining LACBED results with dark-field images showing the presence of interfacial steps and high-resolution images from cross-sectional samples, a more detailed understanding of the growth interrupt layers is derived.