Direct Observation of Strain Distribution in InP/In1-xGaxP Heterointerfaces by the Compositional Analysis by Thickness Fringe Method

Compositional analysis by the thickness-fringe (CAT) method is applied to evaluate the strain distribution at the InP/In1-x Ga x P heterointerface in the direction of epitaxial growth. It has been found that the strain due to the lattice mismatch between In1-x Ga x P and InP is clearly detectable as a bending of the equal-thickness fringe in the CAT image. The crystal planes in the strain field bend as a result of lattice distortion, causing both change in the Bragg condition of the electron diffraction and fringe bending. The fringe bending depends on the amount of lattice mismatch. The strain distribution is analyzed by comparing observed and simulated CAT images. The CAT method is also useful for evaluating the strain distribution with a high spatial resolution.