Study of GaN coalescence by dark‐field X‐ray microscopy at the nanoscale

• Published in: Journal of applied crystallography Vol. 56; no. 3; pp. 643 - 649
• Main Authors: Wehbe, Maya, Charles, Matthew, Baril, Kilian, Alloing, Blandine, Pino Munoz, Daniel, Labchir, Nabil, Zuniga-Perez, Jesús, Detlefs, Carsten, Yildirim, Can, Gergaud, Patrice
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.06.2023; Blackwell Publishing Ltd
• Subjects: characterization; Coalescence; dark‐field X‐ray microscopy; Diffraction; diffraction imaging; Extreme values; Gallium; gallium nitride; Gallium nitrides; Imaging techniques; Microscopy; Misalignment; Nanostructure; nano‐pillars; Optoelectronics; Physics; Pyramids; Research Papers; Silicon dioxide; Spatial discrimination; Spatial resolution; synchrotron radiation; coalescence; nano-pillars; diffraction imaging; gallium nitride; dark-field X-ray microscopy; characterization; synchrotron radiation; nanopillars
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S160057672300287X

This work illustrates the potential of dark‐field X‐ray microscopy (DFXM), a 3D imaging technique of nanostructures, in characterizing novel epitaxial structures of gallium nitride (GaN) on top of GaN/AlN/Si/SiO2 nano‐pillars for optoelectronic applications. The nano‐pillars are intended to allow independent GaN nanostructures to coalesce into a highly oriented film due to the SiO2 layer becoming soft at the GaN growth temperature. DFXM is demonstrated on different types of samples at the nanoscale and the results show that extremely well oriented lines of GaN (standard deviation of 0.04°) as well as highly oriented material for zones up to 10 × 10 µm2 in area are achieved with this growth approach. At a macroscale, high‐intensity X‐ray diffraction is used to show that the coalescence of GaN pyramids causes misorientation of the silicon in the nano‐pillars, implying that the growth occurs as intended (i.e. that pillars rotate during coalescence). These two diffraction methods demonstrate the great promise of this growth approach for micro‐displays and micro‐LEDs, which require small islands of high‐quality GaN material, and offer a new way to enrich the fundamental understanding of optoelectronically relevant materials at the highest spatial resolution. In this article, highly oriented small structures of gallium nitride grown on top of silicon nano‐pillars are characterized by dark‐field X‐ray microscopy for optoelectronic applications such as micro‐LEDs.