Extended Data Fig. 3: Changes in the valence band structure of strained GaN.
From: Observation of 2D-magnesium-intercalated gallium nitride superlattices
a, Calculated bandgap changes of wurtzite GaN and internal parameter under high uniaxial compressive strain. Insets depict schematic representations and iDPC-STEM images of unstrained GaN lattices outside the MiGs structure and strained GaN lattices within the MiGs structure. b, Calculated electronic band structures of unstrained wurtzite GaN (left) and −10% strained wurtzite GaN (right). c, STEM image of an FIB-prepared thick GaN lamella with MiGs structure distributed on the surface, where a magnified bright field (BF)-STEM image is placed on the right, with an inset showing a HAADF-STEM image of the area in the green dashed box of the BF-STEM image, confirming the presence of MiGs structures. Thicker lamella is required for STEM- cathodoluminescence (CL) analysis which compromises the STEM imaging resolution. d, STEM-CL spectra comparing photoemissions from nano-scale sampling locations far from, close to, and inside the MiGs structures formed by annealing metallic Mg deposited on an n-type GaN substrate. Positions of sampling locations are indicated in c accordingly.
