Step-controlled strain relaxation in the vicinal surface epitaxy of nitrides.
On-axis and vicinal GaN/AlN/6H-SiC structures grown under identical conditions have been studied by x-ray diffraction and transmission electron microscopy to demonstrate the distinctive features of vicinal surface epitaxy (VSE) of nitrides on SiC. In VSE, the epilayers are tilted from the substrate due to the out-of-plane lattice mismatch (Nagai tilts), and the in-plane mismatch strains are more relaxed. The majority of misfit dislocations (MDs) at the vicinal AlN/6H-SiC interface are found to be unpaired partial MDs that are geometrically necessary to correct the stacking sequences from 6H to 2H. This mechanism indicates that it is possible to develop "step-controlled-epitaxy" strategies to control strain relaxation by adjusting the substrate offcut angles.
Huang
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XR
Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275, USA. xiahuang@ms.cc.sunysb.edu
Bai
J
J
Dudley
M
M
Wagner
B
B
Davis
R F
RF
Zhu
Y
Y