HIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPY OF ALAS GAAS INTERFACIAL STRUCTURE IN THE 110 PROJECTION/

We have established an imaging condition of [110] high-resolution tran smission electron microscopy (HREM) for edge-on observations of AlAs/G aAs interfacial step structures. It is shown that [110] HREM images of GaAs and AlAs show a remarkable contrast around a specimen thickness equivalent to the GaAs extinction distance due to a large difference i n {111} amplitudes between GaAs and AlAs. A specimen preparation techn ique in which chemical etching was used to remove ion milling artifact s was also developed to accomplish this observation. Using this HREM m ethod, we have made observations of AlAs/GaAs interfaces grown by mole cular beam epitaxy, giving information about the straightness of the i nterfacial step edges and the distribution of step intervals. These re sults show a marked difference in the interfacial step structure betwe en steps parallel to [110BAR] and steps parallel to [110].