Observation of pn junction in GaAs using defocus CBED pattern

Abstract Nanoscale analysis of pn-junctions in crucial semiconductors like GaAs is vital but challenging, especially for strained hetero-structures where methods like holography and differential phase contrast-scanning transmission electron microscopy face limitations. This study demonstrates the application of defocus convergent-beam electron diffraction (CBED) using conventional TEM to observe GaAs pn-junctions. Distinct dark-and-white line contrasts, independent of defocus sign and attributed to electron deflection by a built-in potential, were observed and confirmed by simulations. While lattice-distortion-sensitive higher-order Laue zone (HOLZ) lines showed neither splitting nor bending in this homojunction, the results highlight defocus CBED’s potential for future simultaneous analysis of potential (via line contrast) and distortion (via HOLZ lines) in complex semiconductor interfaces.