ブリッジマン法によるZnSe単結晶の成長

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ZnSe is a promising material for preparing blue light emitting diodes due to its suitable direct band gap of 2.7eV at room temperature. Recently, there is an urgent demand for large area and high quality ZnSe substrates for homoepitaxial growth. In order to satisfy above requirement, several growth methods have been developed. Special emphasis in these methods is focused on the melt growth because of its productivity. However, owing to the different vapor pressures of zinc and selenium, the deviation from the stoichiometric compositions of the melt occurs during melt growth. In order to overcome this problem, we have adopted a closed double-crucible assembly consisting of an inner pBN crucible and an outer molybdenum capsule and examined a suitable growth condition. As an optimum growth condition, the superheating temperature of 76℃, the temperature gradient at the growth interface of 30℃/cm and growth rate of 3.6mm/h have been determined. Using above growth conditions, the twin-free greenish yellow ZnSe single crystals of cylindrical shape with diameter of 12mm and length of 55mm have been obtained by the polycrystalline seeded vertical Bridgman method. Chemical etching on the cleaved (110) plane showed that the average value of etch pit density (EPD) is about 2.0×(10)^5(cm)^<-2>. The rocking curves of 4-crystal X-ray diffraction showed the 19 arcsec in full-width at half-maximum (FWHM). The photoluminescence (PL) spectra at 4.2K showed the resolved intensive bound exciton emission lines and the very weak donor-acceptor pair (DAP) emission bands and their phonon replicas. On the other hand, the deep level emission bands were not almost observed. Above all results suggest that the ZnSe single crystals grown by the present method is of very high quality.ZnSetwinsingle crystalBridgmangrowth ratesuperheating temperatureetch pit density (EPD)X-ray diffraction (XRD)photoluminescence (PL)
東北大学の論文

ブリッジマン法によるZnSe単結晶の成長

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