Selective growth of AlGaAs system in III-V compounds with various epitaxial growth methods has been briefy described on the morphologies in the grown layers. Selective area growth of GaAs and AlGaAs on patterned GaAs sustrates with low-pressure organometallic vapor phase epitaxy is reviewed in detall. The GaAs-AlGaAs double heterostructure grown in etched grooves of a semi-sin-sulating GaAs substrate has been used for the fabrication of TJS lasers, whose characteristics have showed the excellent quality of the embedded layers . The crystallographic orientation dependence of growth rates are also described and the growth mechanism discussed.

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A new high pressure LEC pulling system with an X-ray imaging apparatus has been developed. We have widely applied this system for in-situ observation of III-V crystal growth, development of novel synthesis and growth technique, and fundamental studies such as fluid flow analysis. The system composed of an in-house modified high pressure puller, MSR-6RA (Cambridge Instrument Co.) and an X-ray imager linked to a real-time image processor which suppresses the back ground noise and enhances the X-ray image. In-situ observation of the meniscus clarifies the relationship between its shape and the crystallinity in the seeding procedure. The observation of the solid-liquid interface during LEC GaAs crystal growth has been achieved for the first time. The difference between the crystal diameter calculated from the derivative weight gain signal and real diameter observed by X-ray image was analyzed.

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Some kinds of binary oxide compounds used for the optical applications as single crystals exhibit common nonstoichiometric natures. The melt of eutectic composition at nonstoichiometric component deficient side coexist in equilibrium with the crystal of chemical composition close to the stoichiometry. On the basis of this point, a model for single crystal growth from the melt near the eutectic point is proposed by using the travelling solvent floating zone method in order to control nonstoichiometry. NdGG (Nd_<3+χ>Ga<_5-χ>O<_12>) single crystal grown by this method has a lattice constant of 12.505Å which is close to that of the stoichiometric composition (12.504Å). Moreover, it is revealed from polarizing microscopic observation that the compositional variation due to the nonstoichiometry has been diminished in the NdGG crystal. This result is contradictory to the usual consideration based on the BPS model where any variations in growth conditions will lead to compositional variations if such nonstoichiometric crystals are grown at other than the congruently meling composition.

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