Range and damage distribution for 50 keV He implantation into GaN calculated using SRIM superimposed on bright-field underfocus (bottom) and overfocus (upper) images of the cross section of a GaN sample implanted with at . The implanted zone is divided into four regions named A, B, C, and D corresponding to different microstructures.
Magnification of the transition zone between C and D regions, showing the diffraction contrast induced by DLs in the (0001) planes, which appear as dark lines parallel to the surface sample (in this image the surface is horizontal).
Cross-sectional TEM micrograph of region D showing a rod-shaped cavity in He-implanted GaN at . (a) HRTEM micrograph of the rod-shaped cavity emitting a DL (arrow). Some DLs are also present in the picture. (b) The digital Moiré pattern showing the compressive strain field around the defect (dashed lines have been drawn as guide for eyes).
Ball-and-stick representations of one cavity, with N atoms as small blue spheres and Ga atoms as big magenta spheres. (a) Simulation cell with one cavity in the center. Only atoms in the vicinity of the cavity are shown for clarity. (b) Slice along the 0001 direction showing the inner surface of one relaxed cavity ( width).
HRTEM micrograph of the bottom part of region C showing one chaplet of cavities (arrows) lying along the edge of the DLs.
(a) Experimental focus series of the rod-shaped cavity imaged in Fig. 3 and (b) calculated focus series of an empty cylindrical void. The defocus value is indicated in nanometer in the bottom right corner.
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