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A variety of BeMgZnSe–ZnSe- as well as BeTe-based quantum-well structures has been fabri- cated and investigated. BeTe buffer layers improve the growth start on GaAs substrates drasti- cally compared to ZnSe/GaAs. The valence-band offset between BeTe and ZnSe has been determined to be 0.9 eV (type II). Due to the high-lying valence band of BeTe, a BeTe–ZnSe pseudograding can be used for an efficient electrical contact between p-ZnSe and p-GaAs. BeMgZnSe quaternary thin-film structures have reproducibly been grown with high struc- tural quality, and rocking curve widths below 20 arcsec could be reached. Quantum-well structures show a high photoluminescence intensity even at room temperature.

Using angle-resolved synchrotron-radiation photoemission spectroscopy we have determined the dispersion of the valence bands of BeTe(100) along ΓX, i.e. the [100] direction. The measurements are analyzed with the aid of a first-principles calculation of the BeTe bulk band structure as well as of the photoemission peaks as given by the momentum conserving bulk transitions. Taking the calculated unoccupied bands as final states of the photoemission process, we obtain an excellent agreement between experimental and calculated spectra and a clear interpretation of almost all measured bands. In contrast, the free electron approximation for the final states fails to describe the BeTe bulk band structure along ΓX properly.

Beryllium chalcogenides have a much higher degree of covalency than other II–VI compounds. Be containing ZnSe based mixed crystals show a significant lattice hardening effect. In addition, they introduce substantial additional degrees of freedom for the design of wide gap II–VI heterostructures due to their band gaps, lattice constants, and doping behavior. Therefore, these compounds seem to be very interesting materials for short wavelength laser diodes. Here, we report on the first fabrication of laser diodes based on the wide band gap II–VI semiconductor compound BeMgZnSe. The laser diodes emit at a wavelength of 507 nm under pulsed current injection at 77 K, with a threshold current of 80 mA, corresponding to 240 A/cm2.

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