Band offsets in cubic GaN/AlN superlattices

The presently unknown band offset in nonpolar cubic GaN/AlN superlattices is investigated by inter-sub-band and interband spectroscopies as well as ab initio calculations. On one hand, the conduction-band offset (CBO) has been determined from the comparison of the measured transition energies with model calculations within the effective mass approximation. On the other hand, the valence-band offset (VBO) and the CBO are accurately simulated by calculating many-body corrections within the $\mathit{GW}$ approximation on top of hybrid-functional density functional theory calculations. Thus, a CBO of $(1.4\ifmmode\pm\else\textpm\fi{}0.1) \mathrm{eV}$ and a VBO of $(0.5\ifmmode\pm\else\textpm\fi{}0.1) \mathrm{eV}$ is obtained as a result of both approaches.