Diffuse X-ray scattering from misfit dislocations at semiconductor hetero-interfaces

Abstract

X-ray diffuse scattering in (001) InGaAs/(AlGa)As transistor structures of high electron mobility was observed for structures whose InGaAs channel thickness substantially exceeded the critical thickness for misfit dislocation formation. The diffuse scattering was determined to originate from misfit dislocations, as confirmed by plan-view transmission electron microscopy. Diffuse scattering was measured using triple-axis X-ray diffraction, which showed that the diffuse scattering was sensitive to the density and direction of the misfit dislocations. Using transmission electron microscopy for calibration, we determined that the diffuse scattered intensity was directly proportional to the dislocation density. For samples with misfit dislocations along only (110), diffuse scattering was confined to a crystallographic direction that was perpendicular to the misfit segments, but for samples with thicker InGaAs layers (and with misfit segments in both (110) directions) diffuse scattering extended along all azimuthal directions. We also determined that observation of directional diffuse scattering provided a more sensitive means of detecting misfit segments than other commonly used techniques.