Integral Monolayer-Scale Featured Digital-Alloyed AlN/GaN Superlattices Using Hierarchical Growth Units

Acquiring AlN/GaN digital alloys with matching coherent lattices, atomically sharp interfaces, and negligible compositional fluctuations remains a challenge. In this work, the nature and formation mechanism of the constituent elements of AlN and GaN atomic layers growth was examined by first-principle calculations and experimental demonstration. On the basis of the calculated formation enthalpies, we developed a hierarchical growth method wherein AlN and GaN growth units are digitally stacked layer by layer through metal organic vapor-phase epitaxy, which involves the growth sequence instantaneously to control chemical potentials of the hierarchical growth units under different atmospheres. High-resolution X-ray diffraction and transmission electron microscopy confirmed that the hierarchical GaN and AlN growth units of digital-alloyed AlN/GaN structures had coherent lattices, abrupt interfaces, and integral monolayers at the atomic scale. The cathodoluminescence properties featured with single emission, combined with theoretical results, demonstrated the capability of electronic energies via the digital-alloyed AlN/GaN superlattices. These results provide a basis for the realization of other digital-alloyed nitride semiconductors.