Abstract
Twin boundaries found to occur in ZnSe epitaxial layers grown by metal-organic vapour phase epitaxy on {100} Ge substrates have been studied using high-resolution transmission electron microscopy. These twin boundaries are of the {111} type and, because of the polarity of the sphalerite (ZnSe) structure, can in principle exist as three different sub-types: neutral, P-type and N-type. Comparison of experimentally recorded images with extensive computer simulations of all three types of twin boundary show that while lattice images unique to each twin type can be found, it is possible to confuse the various types when the effects of crystal misorientation are considered. The present results, however, indicate that only the neutral type of twin boundary has been found so far in these epitaxial layers.