Abstract: The technique for preparing cross-sectional specimen of semiconductor for TEM is shown. In such specimens prepared with the technique, an unexpected periodic compositional modulation in the fine low-dimensional structure named Fine Low Dimensional Modulated Fringes of GaAs/AlGaAs multilayers grown by MBE are observed. Some new patterns of dislocations, defects and microtwins etc. in GaAs/Si grown by both MBE and MOCVD are remarked. The technology can be adapted to the study of other systems of semiconductor materials also.