%0 Journal Article
%A Ji, K.
%A Schnedler, M.
%A Lan, Q.
%A Carlin, J.-F.
%A Butté, R.
%A Grandjean, N.
%A Dunin-Borkowski, R. E.
%A Ebert, Philipp
%T Origin of giant enhancement of phase contrast in electron holography of modulation-doped n -type GaN
%J Ultramicroscopy
%V 264
%@ 0304-3991
%C Amsterdam
%I Elsevier Science
%M FZJ-2024-05005
%P 114006 -
%D 2024
%X The electron optical phase contrast probed by electron holography at n-n+ GaN doping steps is found to exhibit a giant enhancement, in sharp contrast to the always smaller than expected phase contrast reported for p-n junctions. We unravel the physical origin of the giant enhancement by combining off-axis electron holography data with self-consistent electrostatic potential calculations. The predominant contribution to the phase contrast is shown to arise from the doping dependent screening length of the surface Fermi-level pinning, which is induced by FIB-implanted carbon point defects below the outer amorphous shell. The contribution of the built-in potential is negligible for modulation doping and only relevant for large built-in potentials at e.g. p-n junctions. This work provides a quantitative approach to so-called dead layers at TEM lamellas.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ 38878506
%U <Go to ISI:>//WOS:001257778200001
%R 10.1016/j.ultramic.2024.114006
%U https://juser.fz-juelich.de/record/1029152