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| Home > Publications database > Surface Calibrated Electron Holography: Anomalous Strain Relaxation and Minimization of Polarization Changes at III-Nitride Hetero-Interfaces |
| Home > Publications database > Surface Calibrated Electron Holography: Anomalous Strain Relaxation and Minimization of Polarization Changes at III-Nitride Hetero-Interfaces |
| Conference Presentation (Plenary/Keynote) | FZJ-2023-01102 |
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2023
Abstract: Polarization and electron affinity changes at Al0.06Ga0.94N/GaN and In0.05Ga0.95N/ Al0.06Ga0.94N interfaces are quantified by off-axis electron holography (EH) in transmission electron microscopy (TEM), in conjunction with scanning tunneling microscopy and spectroscopy, as well as self-consistent simulations of the electrostatic potential and electron phase maps. The central problem of quantitative EH is that at the surfaces of the thin TEM lamellae a defect-induced pinning occurs, which alters the phase contrast. Therefore, we calibrated the electron optical phase maps using a delta-doped layer at the GaN buffer/substrate interface by determining the energy of the pinning level at the surface to 0.69 eV above the VBM (consistent with pinning by nitrogen vacancies). The such calibrated EH provides quantification of the key interface properties: The biaxially relaxed In0.05Ga0.95N/ Al0.06Ga0.94N interface exhibits polarization and electron affinity changes as theoretically expected. However, at the Al0.06Ga0.94N/GaN interface anomalous lattice relaxations and vanishing polarization and electron affinity changes occur, whose underlying physical origin is anticipated to be total energy minimization by the minimization of Coulomb interactions between the polarization-induced interface charges.
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