Dislocation reactions in a semipolar gallium nitride layer grown on a vicinal Si(001) substrate using aluminum nitride and 3$C$–SiC buffer layers

The interaction between $\mathbf{a}+\mathbf{c}$-type and $\mathbf{a}$-type dislocations in thick (up to 14 $\mu$m) semipolar GaN layer grown by hydride vapor phase epitaxy on a 3$C$ SiC/Si(001) template has been detailed investigated by means of transmission electron microscopy. It is shown, that the expansion of a dislocation half loop with Burgers vector $\mathbf{b}=\frac{1}{3}\langle1\bar{2}10\rangle$ during cooling process can be blocked by its reaction with a threading dislocation with $\mathbf{b}=\frac{1}{3}\langle\bar{1}2\bar{1}3\rangle$ to form a dislocation segment with $\mathbf{b}=\langle0001\rangle$. This dislocation reaction is discussed in terms of the energy relaxation. The approximation estimate made within the linear tension approach gives the total energy gain $\sim$7.6 eV/$\mathring{\mathrm{A}}$ (that is, in general, $\sim$45.6 keV for the observed screw dislocation segment of length 600 nm formed as a result of the reaction). Using the core energy calculations, the dislocation core contribution was also estimated as $\sim$19.1 keV.