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We report growth optimization of molecular beam epitaxy (MBE) grown ZnSe on GaAs (0 0 1) substrate tilted by 15° toward [1 1 0] in terms of beam equivalent pressure (BEP) ratio and growth temperature. A LT-ZnSe buffer was grown to reduce the formation of Ga–Se bonding, a well-known source of defect generation, due to interdiffusion through the heterointerface in the initial stage of growth. The ZnSe layer was further optimized by low-temperature-grown (LT-ZnSe) buffer. The optical and structural properties of the ZnSe film with LT-ZnSe and GaAs buffer are also analyzed by photoluminescence spectroscopy (PL), X-ray diffraction (XRD), and secondary ion mass spectroscopy (SIMS), which show very large intensity ratio of near-band-edge emission to deep level emission, narrow XRD peak width of (0 0 4) rocking curves, and abrupt ZnSe/GaAs heterointerface under the optimum growth condition, respectively. The optimum growth conditions are BEP ratio ( P Se / P Zn ) of 3 and growth temperature of 310°C with an LT-ZnSe buffer grown at 250°C.

This article demonstrates the effect of the thin low-temperature-grown ZnSe buffer layer (LT-ZnSe) in improving crystallinity of ZnSe-based films grown on GaAs substrate. Especially, the density of stacking fault defects, which is normally observed in ZnSe-based films grown on GaAs substrate, can be well reduced by inserting a thin ZnSe buffer layer grown at sufficiently low temperature between ZnSe/GaAs heterostructure. A ZnSe film with stacking fault densities as low as ∼2×10 6 /cm 2 was obtained by growing on the LT-ZnSe/GaAs buffer layers, in contrast, ∼8×10 8 /cm 2 was obtained by directly growing on GaAs substrate. The Frank-type stacking faults was dominant for films grown with LT-ZnSe, meanwhile, Shockley-type stacking faults was dominant for films grown without LT-ZnSe buffer. At the initial stages of ZnSe growth, three-dimensional growth mode is considerably suppressed with LT-ZnSe buffer. The improvement of crystallinity in the ZnSe film with LT-ZnSe and GaAs buffer is also evidenced by low-temperature photoluminescence spectroscopy and high-resolution X-ray diffraction, which show very large intensity ratio of near-band-edge emission to deep level emission and narrow X-ray diffraction peak width of (0 0 4) rocking curve with 92 arcsec, respectively.

We have studied the growth and properties of ZnSe/BeTe superlattices by molecular beam epitaxy for two interface configurations, which are basically characterized by a “ZnTe” and a “BeSe” interface layer. The interface properties for the two interface configurations have been studied by means of reflection high energy electron diffraction, high resolution X-ray diffraction, and photoluminescence. It is shown that the optical and structural properties of ZnSe/BeTe superlattices are improved with a ZnTe interface compared to a BeSe interface.

We report a novel structure of a selectively grown buried-ridge (SGBR) type nitride-based laser diode structure grown on sapphire and lateral epitaxial overgrowth (LEO) substrates by metal-organic chemical vapor deposition (MOCVD). The AlGaN layers were designed for current confinement into ridge as well as to enhance lateral optical confinement by introducing an index difference between MQW and AlGaN layers in the lateral direction. The I–V characteristics of SGBR structure on LEO substrate showed no leakage current upto a reverse bias of −10 V. From an EL image through transparent metal, we demonstrated that the current path was well defined into the ridge region.

Photoelectrochemical water reduction using n-type GaN in electrolytes with/without alcohol was investigated. For both cases, hydrogen evolution from counterelectrode was observed without bias. Hydrogen gas amount using 1.0 mol/L NaOH electrolyte with alcohol was approximately double compared to that without alcohol where the total current flow charges are similar at 300 min. The amount of hydrogen evolution was almost coincidence with the amount calculated from the total charge flow. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The power dependence and the temperature dependence of the luminescence intensity of ultra-thin pseudomorphic ZnSe quantum wells, grown on high index GaP substrates were investigated. A blue shift of PL with power excitation is mainly related to the band filling of interfacial ZnSe clusters while it is found that the piezoelectric field has only a small influence. Luminescence spectra of ultra-thin ZnSe/ZnS single quantum wells are characterized by an excitation dependent excitonic localization phenomenon.

This letter presents a reliable and very easy method for selective growth of polarity controlled ZnO films on (0001) Al2O3 substrates by plasma-assisted molecular-beam epitaxy. Cr-compound intermediate layers are used to control the crystal polarity of ZnO films on (0001) Al2O3. ZnO films grown on rocksalt structure CrN/(0001) Al2O3 shows Zn polarity, while those grown on rhombohedral Cr2O3∕(0001) Al2O3 shows O polarity. Possible interface atomic arrangements for both heterostructures are proposed.