BeTe-ZnSe heterojunctions are interesting model systems, where the interface is made of materials which are almost lattice matched, but have no common anion nor cation. As a consequence, there are two interface configurations, which are basically reflected by a "ZnTe" and a "BeSe" interfacial layer. To a certain extent, the interface configuration can be controlled by the MBE growth mode, and has an important impact on structural, electronical and optical properties of the heterojunction. The two possible interface configurations drastically influence the strain state and the band offset. The averaged lattice constant of small period BeTe-ZnSe superlattices can be used for an analysis of the interface composition. Spatially indirect electron-hole recombination is linearly polarized due to the particular bond orientation at the interface. Surface emitting type-II LEDs with a linear polarized emission have been fabricated.