Lattice parameter measurement in quaternary (InGaAsP) layers on InP substrates using convergent beam electron diffraction.

Using x-ray diffraction, one is able to routinely measure lattice parameters to several parts in 10(4) for macroscopic specimens. Measuring the lattice parameters for quaternary (InGaAsP) device structures several microns in width is not, however, usually feasible. Convergent Beam Electron Diffraction (CBED), one of the techniques available on a modern transmission electron microscope (TEM), is sensitive to such small changes in lattice parameter for regions several hundred angstroms in width. Unfortunately, dynamical diffraction effects prevent easy extraction of a lattice parameter from CBED patterns. For this reason, we have chosen to calibrate the position of CBED features with x-ray lattice parameter measurements obtained from planar quaternary layers grown on InP substrates.