Structural Analyses of Metal/GaAs Contacts and Ge/GaAs and AlAs/GaAs Heterojunctions

Abstract

Cross-sectional observations of interface structures at high magnification by TEM and STEM offer excellent lateral and depth resolution which are not available by other analytical techniques. This technique has recently been applied by the author to study metal/GaAs contacts and MBE-grown semiconductor heterojunctions. Specific observations on alloyed Au-Ni-Ge/GaAs and Pd/GaAs interfaces and on epitaxially grown Ge-GaAs and AlAs-GaAs superlattice structures are reviewed in this paper. The high spatial resolution of the energy dispersive x-ray analysis performed in a STEM is most useful in the studies of complicated metal/ GaAs interfacial reactions. However, to resolve on an atomic scale the compositional profile across a heterojunction, one has to rely on diffraction technique. The detailed analyses of these interfacial reactions and structures are shown to be essential to the understanding and control of the electronic behavior associated with these interfaces.