Susumu Kondo

Liquid‐phase‐epitaxial growth of single‐crystal LiNbO3 thin film

The phase equilibrium of the LiVO3‐LiNbO3 pseudobinary system has been investigated, and a LiNbO3 single‐crystal thin film has been grown epitaxially onto the substrate by dipping a c‐plate LiTaO3 substrate into a LiVO3 flux solution. An x‐ray rocking curve indicated that the film had a high single crystallinity with good epitaxy. The composition ratio Li/Nb of the film was estimated to be close to the stoichiometric value Li/Nb≈1.0.

Optical waveguide of LiNbO3 thin film grown by liquid phase epitaxy

We report optical waveguiding of a LiNbO3 single−crystal film grown onto a c−plate LiTaO3 substrate by liquid phase epitaxy from a new Li2O−V2O5 flux. A film of about 3−μm thickness supported seven TE and two TM modes. Measurements of the mode indices indicated that the film is a ’’uniform’’ waveguide having constant refractive indices no=2.2884 and ne=2.1914 throughout the film. Attenuation was measured to be 5 and 11 dB/cm for TM and TE, respectively.

A novel encapsulant material for LEC growth of GaSb

Abstract Single crystals of GaSb have been grown by a liquid-encapsulated Czochralski (LEC) technique using a novel encapsulant material. A eutectic composition in the NaCl-KCl binary system was used as the encapsulant. A significant feature was that the oxide film on the GaSb melt pealed off in thin flakes in the encapsulant. Twin-free GaSb single crystals grown on B axis were successfully obtained. Electrical properties were N = (1.0−1.5) × 10 17 cm -3 and μ = 690−740 cm 2 V -1 s -1 at room temperature, exhibiting p-type conduction.

Low dislocation density GaSb single crystals grown by LEC technique

Abstract Dislocation density in LEC-grown GaSb single crystals was studied. It was observed that a thermal shock due to seed-contact to a melt contributed to the generation of dislocations in the crystal. By melting back the dislocation-free seed after contacting the melt, approximately 20–25 mm GaSb single crystals with only a few dislocation pits can be successfully grown.

LPE growth of Li(Nb, Ta)O3 solid-solution thin film waveguides on LiTaO3 substrates

Abstract Li(Nb, Ta)O3 solid-solution thin film optical waveguides were fabricated by liquid phase epitaxial growth from a solution containing V2O5 flux. Phase relations of the LiVO3-Li(Nb1-xTax)O3 systems were studied by differential thermal analysis, and LPE growth of the films was performed on Y-plates of LiTaO3 substrates. Appropriate growth conditions for obtaining high crystallinity films were investigated based on X-ray examinations. Optical waveguiding characteristics such as refractive indices and optical propagation are described.

Temperature variations of lattice parameters of LiNbO3, LiTaO3 and Li (Nb 1−y Tay) O3 solid-solutions

Abstract Temperature variations of the lattice parameters a and c of LiNbO 3 , LiTaO 3 and their solid-solution crystals Li (Nb 1− y Ta y ) O 3 of y = 0.23, 0.40 and 0.73 have been determined with a high-temperature X-ray diffractometer in the temperature range between 25 and 1000°C.

Preparation of paratellurite TeO2

Raw materials for the growth of Paratellurite TeO2 single crystal were prepared by oxidizing metallic Te with boiling concentrated nitric acid, and large single crystals of Paratellurite were successfully grown from the melt. Simulation experiments of the crystal pulling demonstrated the fluid-flow conditions in the melt.

Fabrication of multi-layer optical waveguide by LPE technique

Abstract Multi-layer structure optical waveguides, consisting of Li(Nb,Ta)O 3 and LiTaO 3 thin films, were fabricated on LiTaO 3 substrates (Z- and Y-plates) by LPE technique. Solution compositions appropriate for Li(Nb,Ta)O 3 optical waveguiding layers and LiTaO 3 cladding layers were examined from the viewpoints of lattice matching, refractive indices and saturation temperature for LPE dipping. Based on determined solutions, multi-layer film consisting of Li(Nb,Ta)O 3 and LiTaO 3 were epitaxially grown alternately onto the substrates. Optical propagation losses in Li(Nb,Ta)O 3 waveguiding layers were 0.5 ∼ 0.9 dB/cm.

Direct measurement of temperature dependence of lattice mismatches between LPE-grown Li(Nb,Ta)O3 film and LiTaO3 substrate

Abstract Temperature dependence of the lattice mismatch between several compositions of the liquid phase epitaxial (LPE) grown Li(Nb,Ta)O3 films and a LiTaO3 substrate was directly measured between 1000 and 20°C, using a high-temperature X-ray triple- crystal spectrometer. It was found that faceting occurs in the film when the lattice parameters a and c of the film were sufficiently larger than those of the substrate at the growth temperature, and that cracks along the cleavage planes in the film were caused by the thermal expansion mismatch between the film and the substrate.

High purity LPE growth of InGaAs by adding Al to melt

Abstract InGaAs crystal films lattice matched to InP were grown by LPE process by adding a small amount of Al to the In-Ga-As ternary melt. InGaAs epilayers grown with the addition of Al have a low carrier concentration and a high Hall mobility without long baking times and with no influence on the InGaAs composition. Thermodynamic calculations explained the results for the Al behaviour in the LPE growth process.