Principles of High-Resolution Dopant Profiling in the Scanning Helium Ion Microscope, Image Widths, and Surface Band Bending

Dopant mapping using secondary electrons (SEs) in the scanning helium ion microscope is correlated with the surface charge distributions and electron inelastic mean free path. Numerical results show that the doping contrast is mainly a function of bulk built-in voltages modified by surface band-bending effects within a 3-nm-thick surface layer. The strong surface work function sensitivity of the SE yield and highly suppressed SE
₂
/SE
₁
ratio militate the higher specificity to acceptors (donors), with surface charging constraining the threshold sensitivity to around 10
¹⁷
cm
^-3
in thicker p-layers, compared to ~10
¹⁵
cm
^-3
commonly attainable in the scanning electron microscope.