Hybrid epitaxial semiconductor/superconductor heterostructures have recently shown promise as a platform to realize Majorana zero modes. To pave the way towards the engineering of such heterostructures for quantum information applications, it is imperative to obtain information about their electronic properties at the semiconductor/superconductor interface. Here, we report on recent soft X-ray angle-resolved photoemission experiments to obtain key electronic material parameters for III-V semiconductor/aluminium interfaces, such as effective mass, charge density, and band offset.