Strain-compensated GaInNAs/GaAsP quantum well structures and lasers were grown by gas-source molecular beam epitaxy using a rf-plasma nitrogen radical beam source. Effects of rapid thermal annealing on the optical properties of GaInNAs/GaAsP quantum well structures as well as laser diodes were examined. It was found to significantly increase the photoluminescence from the quantum wells and reduce the threshold current density of the lasers, mainly due to a removal of N-induced nonradiative centers from GaInNAs wells.

We show how positron annihilation can distinguish vacancies in the different sublattices of a binary compound by performing experiments in ZnS x Se 12x layers. We identify the Se vacancies ͑V Se ͒ in N-doped and the Zn vacancies ͑V Zn ͒ in Cl-doped material by the shape of the core electron momentum distribution. The charge of the defect involving V Se is neutral or negative in p-type ZnS x Se 12x , suggesting that V Se is complexed with an acceptor. The concentration of the V Se complexes is high ͑$10 18 cm 23 ͒, indicating that their role is important in the electrical compensation of p-type ZnS x Se 12x . [S0031-9007(96)01393-2]

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A Bragg reflector consisting of a 25-period MnZnSSe/ZnSSE Bragg stack is reported. The II-VI semiconductor structure was grown by molecular beam epitaxy on a GaAs ͑100͒ epilayer. Structural characterization of the Bragg reflector was performed with double crystal x-ray diffraction and transmission electron microscopy. These studies indicated that the epitaxial II-VI structure, whose total thickness is about 2150 nm, remains pseudomorphic with the GaAs substrate. The Bragg stack has a maximum reflectance of 81% at 468 nm. This result shows that fabrication of high reflectance mirrors from epitaxial ZnSe-based II-VI compounds is possible in spite of relatively small refractive index differences between constituent II-VI layers. © 1995 American Institute of Physics.Efficient light emitters operating in the green/blue visible spectral range are required for many applications such as optical data storage, biomedicine, undersea communications, and displays. Recently there has been rapid progress in development of blue/green light emitters made from ZnSebased II-VI compound semiconductors.1,2 For example, an important milestone in this field has been the recent demonstration of room temperature, continuous-wave blue emission from II-VI laser diodes.3,4 Equally impressive progress has been reported in II-VI light emitting diodes ͑LEDs͒, especially for structures that have been grown on ZnSe substrates.5 For optoelectronic applications requiring arrays of emitters ͑e.g., displays and interconnects͒ it is well known that many benefits accrue from engineering the emission normal to the epilayer growth, as for example in vertical cavity surface emitting lasers ͑VCSELs͒ and, of perhaps more importance for displays, planar surface emitting LEDs. Enhanced emission from planar LEDs can be obtained by strategically placing the light emitting region between high reflectance mirrors. Efficient emission with Ͼ10% external quantum efficiency by III-V planar LEDs using such microcavity design has been reported recently. 6 These microcavity LEDs have other advantages over standard planar LEDs such as increased directionality. High reflectance mirrors play a central role in all such advanced VCSEL and LED structures and can be grown either epitaxially or by deposition of dielectric stacks or metals. Epitaxial mirrors are, however, more attractive since sample processing is minimized. In II-VI compound semiconductors fabrication of high quality epitaxial mirrors is especially challenging due to small refractive index differences of compatible constituent mirror materials. These difficulties are compounded by lack of precise data on the optical constants of II-VI materials. In this letter, we report on the growth and characterization of a high reflectance II-VI Bragg mirror consisting of 25 pairs of ZnSSe/MnZnSSe where the optical thickness of each layer is 0 /4 and the design wavelength 0 , is 480 nm. We measure a peak reflectance ͑R͒Ͼ81% at ϭ468 nm. This is the highest reported reflectance of an epitaxially grown II-VI multilayer mirro...

In situ optical reflectometry at the wavelength of 488 nm was employed to control the growth of MgZnSSe/ZnSSe Bragg mirror stacks for the blue-green spectral region. 10-and 20-period layer structures of MgZnSSe/ZnSSe were grown on GaAs ͑100͒ epilayers by molecular beam epitaxy. A room-temperature peak reflectance of 86% was obtained for the 20-period structure at the central wavelength of 474 nm. The results show that, in general, in situ optical monitoring of growth is a viable and simple method for real-time layer thickness control of MgZnSSe/ZnSSe quarter-wave stacks. © 1995 American Institute of Physics.Semiconductor microcavities are being exploited in novel optoelectronic devices such as vertical cavity surface emitting lasers ͑VCSELs͒ and high efficiency planar surface light emitting diodes. Microcavities may also be used for exploring fundamental properties of the coupling of electromagnetic radiation and two-dimensional electronic excitations in quantum wells, i.e., cavity polaritons. 1 In all of these applications high reflectance mirrors are needed.Within the family of ZnSe-based II-VI semiconductors, which are of great importance for the blue-green spectral region, vertical cavity structures have only been realized by means of an epitaxial lift-off ͑ELO͒ method 2 or by selective etching 3 followed by deposition of dielectric or metallic mirrors on both sides of the cavity. However, growing an epitaxial II-VI semiconductor distributed Bragg reflector ͑DBR͒ directly into the layer structure is a more desirable possibility. This approach is very attractive because there are many problems encountered in the ELO and selective etching methods.We have already demonstrated a high reflectance MgZnSSe/ZnSSe quarter-wave stack grown by molecular beam epitaxy ͑MBE͒, 4 which proved the feasibility of fabrication of Bragg mirror stacks from ZnSe-based materials. It was found, however, that MnZnSSe is more difficult to dope p type than MgZnSSe. In addition, MgZnSSe has a larger fundamental band gap than MnZnSSe and, consequently, a smaller refractive index ͑n͒. Therefore, we began to study MgZnSSe/ZnSSe as a new candidate for high reflectance DBR mirrors intended for II-VI devices.Fabrication of high reflectance MgZnSSe/ZnSSe Bragg mirrors is challenging because of structural instabilities, such as compositional variations, which are involved in the growth of ZnSe-based compound semiconductors. We have employed an in situ laser reflectometry method ͑see, e.g., Ref. 5͒ during growth of MgZnSSe/ZnSSe DBRs in order to determine accurately and straight forwardly the /4n layer thicknesses at growth temperature. We used an air cooled argon ion laser emitting at ϭ488 nm. Proper layer thicknesses can be achieved by switching the growth of materials at the extrema of reflected laser beam intensity. In this way the difficulties related to growth rate and compositional variations can be overcome to a large extent.MgZnSSe has been widely used as a cladding layer of blue-green laser diodes. 6,7 The room-temperature band gap (E ...