Stress generation and relaxation in (Al, Ga)N/6$H$-SiC heterostructure grown by plasma-assisted molecular-beam epitaxy

In situ stress generation and relaxation in Al$_{0.25}$Ga$_{0.75}$N/GaN/AlN heterostructure with an overall thickness exceeding 3 $\mu$m in the process of its growth on a 6$H$-SiC substrate by low-temperature plasma-assisted molecular-beam epitaxy at substrate temperatures ranging from 690 to 740$^\circ$C was studied. At room temperature, AlN and GaN layers revealed residual compressive stresses of -2.3 and -0.1 GPa, respectively. This made it possible to avoid cracking during postgrowth cooling of the structure.