Carrier distribution in quantum nanostructures studied by scanning capacitance microscopy

Abstract

We addressed issues related to quantitative carrier profiling by scanning capacitance microscopy (SCM) on doped layers with different dimensions, starting from thick (∼5 μm) uniformly doped Si layers down to Si/Si_1−xGe_x/Si quantum wells with nanometre width. We preliminarily discuss the influence of the SCM hardware on the quantification, by comparing the analyses performed on Si calibration standards with two different atomic force microscopes, i.e. DI3100 by Veeco and XE-100 by PSIA, equipped with different SCM sensors. Furthermore, concentration sensitivity and spatial resolution are deeply discussed considering measurements on special designed samples containing quantum wells of Si_0.75Ge_0.25 layers strained between Si films. Measurements were taken on sample cross-sections and on bevelled samples. A nanometre SCM spatial resolution was demonstrated not only in terms of signal sensitivity, but also in terms of quantitative majority carrier profiling.