[110]HREM OF INTERFACIAL STRUCTURES IN SEMICONDUCTOR HETEROSTRUCTURES

We have established a [110] cross-sectional high-resolution transmissi on electron microscopy (HREM) method to observe atomic structures of s emiconductor hetero-interfaces, We show theoretically that the semicon ductors in a hetero-structure exhibit strong contrast for an EM specim en thickness near their extinction distances, allowing atomic-scale ob servations of the interfacial structures between them. Furthermore, to obtain a clear HREM image, an EM specimen preparation technique is de veloped in which chemical etching is used to remove ion milling artifa cts. This HREM method allows edge-on imaging of interfaces formed alon g the [110] direction; observations of atomic steps at AlAs/GaAs inter faces and a chemically ordered structure at Si/Ge interfaces are demon strated. (C) 1998 Wiley-Liss, Inc.