Shoichi Ozawa

Low loss integrated Mach-Zehnder-interferometer-type eight-wavelength multiplexer for 1480 nm band pumping

We demonstrate an eight-wavelength PLC-MZI multiplexer to realize high-power 1480-nm band pumping units without using polarization combiners. The fiber-to-fiber insertion loss was lower than 1.2 dB by using laser diodes stabilized by fiber Bragg grating.

InP single crystal growth with controlled supercooling during the early stage by a modified LEC method

A new liquid encapsulated Czochralski (LEC) technique for InP single crystal growth has been developed. In order to restrain the generation of twin bondaries from the shoulder of InP crystal by the LEC method, at the beginning of InP crystal growth, we tried to produce growth toward the lateral direction until reaching a 2-inch diameter without forming a cone angle (θ = 90°) by controlling the optimum supercooling of the InP melt. As a result, it was found that although isotropic growth could restrain the twin boundary, anisotropic growth was likely to generate a twin boundary at the completion of lateral growth. After isotropic growth, InP single, crystals were obtained reproducibly. That is, ten single crystal ingots of InP were obtained by this method. Furthermore, the etch pit density (EPD) of InP water with a 2-inch diameter was less than 2000 cm-2, except at the edge of the water, by Zn doping ((3.0-4.0) X 1018 cm-3).

Increase of effective viscosity of molten GaAs and InSb under an axial magnetic field

We have measured the effective dynamic viscosity of molten GaAs and InSb as a function of axial magnetic field by the oscillating vessel method. Effective viscosity of these semiconductor melts is observed to increase with the axial magnetic field intensity in the range of 0 to 5 kG.

In-doped GaAs substrate assessment for thin film applications

Abstract We have evaluated In-doped GaAs from the viewpoint of its use as a substrate for the growth of MOCVD and MBE epitaxial layers. The distribution of misfit dislocations at the undoped GaAs epilayer/In-doped GaAs substrate interface was assessed with X-ray topography and correlated with surface morphology. No significant difference was found in the critical thickness for generating misfit dislocations between the MOCVD and MBE growth method. The stress distribution in samples with misfit dislocations was revealed in their birefringence patterns. The out-diffusion of indium from the substrate to the epilayer was observed in neither MBE nor MOCVD GaAs epilayer growth.

Effects of arsenic ambient controlled LEC GaAs crystal growth technique on residual impurities

Abstract The influence of the arsenic ambient on the residual impurities in LEC GaAs crystals was investigated. It is noted that undoped semi-insulating GaAs crystals are obtained by the arsenic ambient controlled LEC (As-LEC) crystal growth technique even when a quartz crucible and pure polycrystalline GaAs were used. The reaction mechanisms between GaAs and the quartz crucible both with and without an arsenic ambient in the LEC GaAs crystal growth process are discussed.