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Misfit dislocation formation in the heterointerface
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Image of FIG. 1.
FIG. 1.

Real-time MOSS data from heteroepitaxial growth on GaN for , 0.22, and 0.37. The critical thickness for relaxation (circled) and the mean stress relief are indicated for the sample. The other two curves are offset vertically for clarity, and only their critical thickness is indicated.

Image of FIG. 2.
FIG. 2.

XTEM image of a fully coherent heterostructure taken under bright-field imaging conditions with .

Image of FIG. 3.
FIG. 3.

Representative optical micrographs of crack networks for (a) , (b) , and (c) .

Image of FIG. 4.
FIG. 4.

TEM images of a partially relaxed heterostructure: (a) plan-view, weak-beam image taken with ; (b) cross-section view taken in dark field with , tilted off towards [0001], showing misfits in the heterointerface (the region bounded by the two dashed lines); and (c) different cross-section view along taken in bright field with showing a thread+misfit segment (dotted line). The dashed line delineates the heterointerface.

Image of FIG. 5.
FIG. 5.

High-resolution XTEM image along from one of the dislocations in Fig. 4(b) demonstrating that the dislocation is dissociated into partials.

Image of FIG. 6.
FIG. 6.

TEM images of a heavily relaxed heterostructure: (a) plan-view, weak-beam image taken with and (b) cross-section view along taken in bright field with , tilted to show the interfacial dislocations. Arrows highlight several long, straight dislocations similar to those observed in the sample of Fig. 4.

Image of FIG. 7.
FIG. 7.

Hexagonal unit-cell diagrams illustrating possible second-order slip systems that create misfits via glide for {0001}-oriented hexagonal . The cell faces are planes and the bottom hexagonal face is the (0001) heterointerface. The arrow represents the Burgers vector, the shaded plane is the glide plane, and the dashed lines represent the intersection of the glide plane with the {0001} planes bounding the unit cell. The properties of each slip system are listed in Table II.

Image of FIG. 8.
FIG. 8.

XTEM micrographs of slip in GaN grown on patterned sapphire substrates. The nearly horizontal dislocation bands lie in {0001}. In (a), the image is along , and one set of dislocations in glide planes is viewed edge-on, while the half loop in is viewed obliquely; (b) the view is rotated 30° to be along ; and (c) the view is rotated towards .

Image of FIG. 9.
FIG. 9.

The calculated critical thickness for glide and fracture. Also shown are measured critical thicknesses from MOSS. The range in the data comes from upper/median/lower bound estimates given the noise in the curvature plots (e.g., see Fig. 1).

Image of FIG. 10.
FIG. 10.

Schematic view of the wurtzite lattice along . The rectangle has dimensions and . Three parallel glide planes, viewed edge-on, are indicated by the heavy diagonal lines.

Image of FIG. 11.
FIG. 11.

(a) Arrangement of the atoms in planes 1 and 2 from Fig. 10. In this view, looking down upon , the atoms of plane 1 are above those of plane 2. The large arrow shows the Burgers vector , while the smaller arrows are the Read-Shockley partials and (b) shows the arrangement of atoms in planes 2 and 3, with plane 2 on top. The arrows are as before.


Generic image for table
Table I.

Stress relaxation and fracture characteristics of films.

Generic image for table
Table II.

Properties of potential slip systmes in -axis-oriented wurtzite lattices. The letters under “slip system” are for direct comparison to Fig. 7.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Misfit dislocation formation in the AlGaN∕GaN heterointerface