Figure 1

Atomic models of basal stacking faults (BSFs) within the wurtzite structure projected onto the $\left(11\overline{2}0\right)$ plane: (a) $I_1$ type, (b) $I_2$ type, (c) $E$ type (d) $I_3$ type. Stacking sequences are indicated. Large and small circles represent Ga and N atoms, respectively.Reuse & Permissions

Figure 2

Atomic models of (a) a $\left(1\overline{2}10\right)$ prismatic stacking fault (PSF) and (b) a $\left(1\overline{2}10\right)$ stacking mismatch boundary (SMB) in wurtzite GaN projected onto the (0001) plane. White and black circles represent Ga atoms. Nitrogen atoms are omitted because their projection would overlap with Ga atoms.Reuse & Permissions

Figure 3

Selected area electron diffraction pattern recorded from a cross-sectional sample along the $\left[1\overline{1}00\right]$ zone axis, showing the epitaxial relationship between GaN layer and the SiC substrate.Reuse & Permissions

Figure 4

Cross-sectional TEM images: (a) bright field image $(\mathit{g}=11\overline{2}0)$ showing distribution of dislocations with Burgers vector components parallel to $\left[11\overline{2}0\right]$. (b) Dark field image $(\mathit{g}=\overline{1}010)$ showing that basal stacking faults nucleate at the $4H\text{−}\mathrm{SiC}∕\mathrm{AlN}$ interface and propagate through the GaN to the sample surface. A crack formed approximately 100 nm from the AlN buffer layer is marked by an arrow. (c) Bright field image $(\mathit{g}=\overline{1}010)$ of an inclined prismatic stacking fault $\left(P\right)$ bounded by two basal stacking faults. (d) Bright field image $(\mathit{g}=11\overline{2}0)$ taken close to the [0001] zone axis. Prismatic stacking faults formed in $\left(\overline{2}110\right)$ or $\left(1\overline{2}10\right)$ are visible as thin lines coming to the sample surface at a 60° angle. (e) Higher magnification image recorded under a many beam diffraction condition showing zigzaglike configuration of a prismatic stacking fault, which results in an almost vertical propagation of the latter from substrate to the sample surface.Reuse & Permissions

Figure 5

Bright field TEM images of a plan-view sample obtained with two perpendicular $\mathit{g}$-vectors: (a) $\mathit{g}=1\overline{1}00$; parallel lines represent stacking faults formed on the basal plane of GaN. (b) $\mathit{g}=0002$; partial dislocations having a nonzero [0001] component which terminate stacking faults are visible. Small black and white arrows on both images show corresponding places of basal stacking faults terminations by dislocations. Black arrows point to sessile Frank partials dislocations whereas white arrows point to glissile Shockley partials. Areas exhibiting a contrast from inclined prismatic stacking faults are marked by circles. Boundaries of these prismatic stacking faults serve as termination sites for basal stacking faults. Local bending of the GaN layer causes changes in contrast across the images. (c)-(d) Enlargements of (a). (f)-(h) Enlargements of (b).Reuse & Permissions

Figure 6

(a) Selected area electron diffraction pattern recorded from a plan-view sample along the $\left[11\overline{2}0\right]$ zone axis. Streaking of diffraction spots along the [0001] direction arises due to the large number of basal stacking faults. (b) Enlarged part of the diffraction pattern showing additional spots arising from doubled c unit lattice of GaN (marked by white arrows).Reuse & Permissions

Figure 7

High-resolution images of a plan-view sample showing typical basal stacking faults observed: (a) removal of basal plane followed by $1∕3\left[1\overline{1}00\right]$ slip generates the $I_1$ basal stacking fault bounded by a sessile Frank partial dislocation with the Burger vector $\mathit{b}=1∕6\left[2\overline{2}03\right]$. (b) Insertion of an extra basal plane also results in generation of the low-energy $I_1$ basal stacking fault bounded by a sessile Frank partial dislocation with $\mathit{b}=1∕6\left[\overline{2}20\overline{3}\right]$. (c) Shear displacement in the $\left[1\overline{1}00\right]$ direction leads to formation of the $I_2$ basal stacking fault, which is bounded by a glissile Shockley partial dislocation. (d) “Switching” of A or B bilayer to the C position results in formation of the $I_3$ basal stacking fault. Stacking sequences for each basal stacking fault is shown at the left.Reuse & Permissions

Figure 8

(a) High-resolution image recorded down to the ${\left[0001\right]}_{\mathrm{GaN}}$ zone axis of a prismatic stacking fault formed in $\left(\overline{2}110\right)$ or $\left(1\overline{2}10\right)$. (b, c) High-resolution image simulations (defocus $-45.0\mathrm{nm}$; thickness 4.7 nm): (b) based on Drum’s prismatic stacking fault model [Fig. 2a], and (c) based on Amelinkx’s stacking mismatch boundary [Fig. 2b].Reuse & Permissions

Figure 9

(a) Plan-view high-resolution image of an inclined prismatic stacking fault (PSF) (inside dashed box) projected onto the $\left(11\overline{2}0\right)$ plane revealing hexagonal-like contrast. The PFS terminates two $I_1$ basal stacking faults. Stacking sequences on the right and left sides of the image show the $1∕2\left[0001\right]$ shift induced by the inclined PSF. The first $I_1$ changes the stacking sequence from …ABAB… to …ACAC…. This sequence is preserved until the second $I_1$ BSF converts it to …BCBC…. (b) Magnified area inside dashed box in (a). (c) Plan-view HREM image of PSF, which terminates two $I_1$ BSFs. Stacking sequences on the right and left sides are shown. No net displacement in $\left[1\overline{1}00\right]$ induced by BSFs is observed. Although the initial …ABAB… stacking sequence changes to …CACA… when crossing the first $I_1$ boundary, the second $I_1$ boundary restores the initial …ABAB… stacking sequence. A Shockley partial dislocation $(1∕3⟨1\overline{1}00⟩)$, which arises from the termination of the $I_2$ basal stacking fault, is also marked. A second dislocation with an opposite Burgers vector is located to the right, outside the image frame. (d) Magnified area inside dashed box in (c). (e) Schematic representation of termination of two $I_1$ BSFs by PSF, $s$ and $-s$ represent $1∕6\left[10\overline{1}0\right]$ and $1∕6\left[\overline{1}010\right]$ stair-rod dislocations.Reuse & Permissions

Figure 10

(a) Drum’s atomic model [Fig. 2a] of a prismatic stacking fault formed in $\left(\overline{2}110\right)$ or $\left(1\overline{2}10\right)$ planes projected onto the $\left(11\overline{2}0\right)$ plane of GaN. (b) Simulated high-resolution image (defocus $-57.5\mathrm{nm}$; thickness 3 nm) of inclined prismatic stacking fault based on Drum’s models shown in (a).Reuse & Permissions

Figure 11

High-resolution image of a dissociated $1∕3⟨11\overline{2}0⟩$ perfect dislocation into two Shockley partials $(1∕3⟨1\overline{1}00⟩)$ bounding the $I_2$ basal stacking fault. Arrows indicate the positions of the partials. The Burgers contour placed around the $I_2$ BSF shows a closure failure equal to $1∕2\left[1\overline{1}00\right]$. The $I_1$ BSF, marked outside the contour, extends though the entire image from the left to the right, and thus does not influence the contour failure.Reuse & Permissions