Beryllium chalcogenides are semiconductors with a large bandgap. They have a higher degree of covalent bonding than all of the other II-VI compounds. The bond energies of BeSe and BeS are comparable to those of GaN. Due to their bandgaps and their lattice constants they can be incorporated in quaternary mixed crystals which are lattice matched to GaAs. The hardness of II-VI materials containing beryllium offers new possibilities to enlarge the lifetime of laser diodes, emitting in the green and blue spectral range. First double heterostructure laser diodes with beryllium as a constituent have been produced on p-type GaAs substrates by molecular beam epitaxy. Double barrier tunneling structures of tile composition ZnSe-BeTe were realized and investigated in high magnetic fields. Shubnikov-de Haas oscillations were observed in the ZnSe contacts of the devices. [References: 23]
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