Observation of dislocations and their arrays in physical vapor transport-grown AlN single-crystal substrate by synchrotron X-ray topography

Abstract

Dislocations in a single-crystal aluminum nitride bulk substrate have been characterized using synchrotron X-ray topography (XRT). Threading edge dislocations (TEDs) and screw-type dislocations as well as {0001}-plane basal plane dislocations have been observed, and their Burgers vectors were evaluated based on the XRT contrast of these dislocations. Particular attention has been paid to the direction of the Burgers vectors of dislocation arrays composed of TEDs. By analyzing the bright/dark contrast change of these TED arrays when all six different g-vectors (equivalent to g = 11-26) were applied, the directions of the a-axis components of Burgers vectors were determined.

Molten Barium Hydroxide as Defect Selective Drop Etchant for Dislocation Analysis on Aluminum Nitride Layers

“…[4][5][6][7] Dislocations can be imaged, e.g., by transmission electron microscopy (TEM) or X-ray topography (XRT). [4,[8][9][10][11] However, both methods are based on expensive equipment and require sophisticated analysis. Furthermore, TEM requires considerable sample preparation and the investigation is confined to small areas, while XRT is only usable if the dislocation densities are below 10 6 cm À2 .…”

X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals

“…Thus, the dislocations are most likely BPDs. While the Burgers vector of BPDs connecting threading dislocations has been identified as being of type 1 3 h2110i, these seem to appear arc shaped or as half loops instead (Yao et al, 2019). BPDs looking similar to those shown in Fig.…”

“…6(b)-6(d) must be basal plane screw dislocations (BPSs) of type b ¼ l ¼ 1 3 h2110i. To our knowledge, this specific dislocation type has been distinctively identified only once and very recently in PVTgrown AlN material (Yao et al, 2019). The research group suggests thermal stress as the likely cause, indicated by the increased density of the BPSs near the edge of the wafer.…”

“…Additionally, a gradual increase of Á2Â seems to appear along the x position of the wafer, possibly indicating a slight curvature of the whole wafer. As suggested in the literature (Yao et al, 2019(Yao et al, , 2020, AlN wafers may exhibit a curvature of the [0004] planes due to the strain caused by the thermal gradients during growth, as well as the anisotropic cooling post-growth. The resulting convex warp of the N-face basal plane may explain the Á2Â of the prism planes.…”

Dislocation Climb in AlN Crystals Grown at Low-Temperature Gradients Revealed by 3D X-ray Diffraction Imaging

“…In general, spatial distributions of dislocations in AlN crystals with densities below 10 6 cm –2 can be studied by defect-selective etching (DSE), ,, laser scattering tomography (LST), and X-ray diffraction imaging techniques such as X-ray topography (XRT). − …”