Transmission Electron Microscopy of Defects in Epitaxial Layers: In-Situ and Ex-Situ Studies

Heteroepitaxy has become a technologically important process in recent years, for example with the growth of GaAs on Si. We present a review of transmission electron microscope (TEM) studies of GaAs on Si and other epitaxial systems which elucidate the nature and origin of defects in these layers. Additional insight is provided from experiments in which molecular beam epitaxial growth of layers can be performed in-situ in a transmission electron microscope. In our laboratory we have studied CoSi sub 2 /Si, NiSi sub 2 /Si and Ge/Si in this manner. For example, we can directly monitor the onset of the critical thickness transformation and study the dynamic introduction of dislocations.