Low energy Xe milling for the quantitative profiling of active dopants by off-axis electron holography

Off-axis electron holography is a powerful technique that can be used to measure the active dopants in semiconductors. The preparation of thin transmission electron microscopy specimens containing nm-scale regions of interest is extremely challenging and as a consequence ion milling is an essential tool. The exposure of doped specimens to energetic ions creates defects deep in the specimens that trap the active dopants, being the principle cause of what is known as the inactive region. The inactive thickness leads to an underestimation of the dopant potential in the specimens. Here we show that this artifact can be significantly reduced from 140 nm for specimens prepared using only Ga ions at 30 kV to only 10 nm by preparing specimens using 1.5 keV Xe ions for specimens containing p-n junctions with dopant concentrations of 2 x 1018 cm-3.