TY  - JOUR
AU  - Ji, K.
AU  - Schnedler, M.
AU  - Lan, Q.
AU  - Carlin, J.-F.
AU  - Butté, R.
AU  - Grandjean, N.
AU  - Dunin-Borkowski, R. E.
AU  - Ebert, Philipp
TI  - Origin of giant enhancement of phase contrast in electron holography of modulation-doped n -type GaN
JO  - Ultramicroscopy
VL  - 264
SN  - 0304-3991
CY  - Amsterdam
PB  - Elsevier Science
M1  - FZJ-2024-05005
SP  - 114006 -
PY  - 2024
AB  - 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.
LB  - PUB:(DE-HGF)16
C6  - 38878506
UR  - <Go to ISI:>//WOS:001257778200001
DO  - DOI:10.1016/j.ultramic.2024.114006
UR  - https://juser.fz-juelich.de/record/1029152
ER  -