Nanoindentation-Derived Mechanical Properties of Cubic III-Nitrides on MgO(001)-Based Templates: c-GaN, c-InxGa1−xN, and c-InN

Mechanical reliability is an essential prerequisite for III-nitride thin films throughout device fabrication and processing. However, the availability of nanoindentation data for metastable cubic phases remains limited, making cross-study comparisons particularly challenging. In this context, the present work offers a unified compilation of hardness (H) and Young’s modulus (E) values derived from nanoindentation of cubic epilayers grown by plasma-assisted molecular beam epitaxy (MBE) on MgO(001)-based templates, encompassing c-GaN, c-InxGa1−xN alloys (x = 0.26–0.72), and c-InN. The three underlying studies utilize consistent metrological approaches: Berkovich indentation with Oliver–Pharr analysis, polished surfaces exhibiting low root-mean-square (RMS) roughness, and a shared MgO/c-GaN-templated stack. This methodological alignment enables a composition-aware comparison across the c-GaN/c-InxGa1−xN/c-InN series. Consolidated H and E values are examined as functions of the indium fraction, x, while their depth dependence is used to distinguish the film-dominated response from the increasing influence of the template or substrate. Additionally, a focused comparison with representative wurtzite data situates the cubic results within a broader context, while maintaining emphasis on MgO-based heteroepitaxy. Ultimately, the resulting dataset and analysis provide a practical resource for mechanically informed processing and reliability evaluation in cubic III-nitride systems.