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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Dedicated to Professor Dr. K. W. BOER on the occasion of his 70th birthday In 11-VI material based laser diode structures, the role of excitonic processes for stimulated emission is still rather controversially discussed. In this paper, the manifestation of biexciton recombination in high-density luminescence of ZnCdSe/ZnSe quantum wells is investigated by intensity-and polarization-dependent spectroscopy. In spite of their evidence in such spectra, their contribution to stimulated emission in laser diodcs with moderately confining wells is not confirmed, instead, indication of strong Coulomb correlation is given when using the new technique of pump-and-probe excitation spectroscopy. A strong electrooptic effect yielding saturation is found in laser diodes exactly at their lasing wavelength thus being promising candidates for integrated laser-modulation devices.

ZnSe substrates grown by the seeded chemical vapour transport method have been used for homoepitaxial growth by molecular beam epitaxy (MBE). Special attention is paid to mechanically untreated as-grown (001) surfaces and a novel chemical and thermal etching procedure suitable for MBE substrate preparation is proposed. The homoepitaxial layers exhibit excellent optical and structural quality confirmed by low-temperature photoluminescence measurements and high-resolution x-ray diffraction. Light-emitting diodes (LEDs) with five Cd 0.2 Zn 0.8 Se quantum wells and ZnSe as barrier material have been fabricated. Using photolithographic and wet-etching techniques, electrical contacts were realized from the top of the devices. The LEDs possess good rectifying properties at room temperature and emit bright green light at 511 nm with a full width at half maximum of only 65 meV. The external quantum efficiency of the devices (up to 0.8%) is discussed in detail.