Specimen preparation for off-axis electron holography using focused ions, energy filters and laser beams

Focused ion beam milling is routinely used to prepare specimens with nm-scale site specificity for examination by transmission electron microscopy. Although low-energy milling techniques can be used to prepare excellent specimens for many TEM-based techniques, the case is more complicated for dopant profiling. Off-axis electron holography can in principle be used to provide 2D dopant maps of semiconductor devices. However, artefacts such as Ga implantation and the introduction of defects deep in the crystalline regions of the specimens significantly change the properties of the doped semiconductors. In this paper we discuss methods that can be used to remove the artefacts that are present in FIB-prepared semiconductors.