Characterization of interfacial topography in lattice strained InxGa1−xAs/GaAs heterostructures by the weak beam imaging technique

Abstract

A TEM (transmission electron microscopy) weak beam imaging technique is introduced for the characterization of interfacial topography in lattice strained In_xGa_1−xAs/GaAs heterostructures. The interpretation of the electron diffraction contrast in this imaging mode was based on a calculation using the kinematic theory for electron diffraction. It was found that fringes that were induced by the presence of the strained layer in the material could be observed. The main contrast features of the fringes predicted by the theoretical calculation, such as the periodicity of the fringes and the dependence of the intensity of the fringes on the thickness of the strained layer, were in agreement with experimental observations. Variation of the thickness of strained layers could be characterized using this mode of imaging and, under certain conditions, variations in thickness on a monolayer scale could be determined with a spatial resolution of about 10 nm in the plane of the layers.