Direct measurement of lateral elastic modulations in a zero-net strained GaInAsP/InP multilayer

Abstract

A zero-net strained GaInAsP/InP(001) multilayer grown by gas source molecular beam epitaxy exhibits large interfacial undulations and an orthorhombic modulated distortion, which are attributed to elastic relaxation of tensile layers. It is examined by high resolution transmission electron microscopy in order to directly determine the strain distribution in the (11̄0) plane. The interplanar spacings are found to be laterally modulated along the [110] direction within tensile and compressive layers. The interplanar spacing modulation is perfectly correlated to the interfacial morphology. Therefore, the strain is not homogeneous but concentrated along [11̄0] oriented lines. Large variations of (110) interplanar spacings up to 3.5% have been measured, while the lattice mismatch between tensile and compressive layers is only 2%. The observed strain distribution is qualitatively consistent with an elastic relaxation mechanism of the tensile layer. Different other effects are reviewed. Surface relaxation effects due to sample thinning are qualitatively discussed. It is also shown that nonplanar interfaces between tensile and compressive layers strongly account for the stress distribution.