N. Murakami

Drop experiments on crystallization of InGaSb semiconductor

Abstract Drop experiments have been performed to study the crystallization of InGaSb under different gravity conditions. Formation of spherical projections on the surface of InGaSb during its crystallization was in situ observed using a high-speed CCD camera. Spherical projections showed dependence on gravity during its growth. The projections formed under microgravity were almost spherical, whereas the projection formed under normal gravity was not perfectly spherical. Indium compositions in the spherical projections were found to vary with temperature.

Microravity experiments on melting and crystallization of InGaSb

Abstract Drop experiments have been performed to study the crystallization of In0.05Ga0.95Sb and the melting behaviors of InSb and GaSb under different gravity conditions. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature. Melting velocities of InSb and GaSb crystals under the microgravity condition were found to be faster than those under normal gravity condition (1G).

Effect of gravity on InGaSb crystal growth

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In0.1Ga0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth.

A numerical study of the buoyancy convection occurring during the formation of InGaSb solution in a GaSb/InSb/GaSb sandwich system

The formation process of an InGaSb solution in a GaSb/InSb/ GaSb sandwich system was numerically studied by considering the effects of various parameters such as temperature gradient, heating rate, crystal width, thickness of an ampoule wall, and gravity levels. The selected reference temperature at fixed point was increased up to 650°C (heating process) and then kept constant (holding process). Numerical results showed that under the 1G condition, the solutal buoyancy convection is dominant during the heating process, but its strength gradually decreases during the holding process. The initially symmetric crystal-melt interface becomes asymmetric in shape with the increasing temperature, and then the interface at the end of the heating process broadens towards the bottom of the solution. The deformation of the interface decreases with the increasing temperature gradient. Similar effects were observed with the increase in the thickness of the ampoule wall. This implies that the quartz ampoule plays the role of thermal insulator. As expected, the model shows that a reduced gravity level is very effective in suppressing the buoyancy convection in the solution. In order to achieve a diffusion dominant mass transfer in the solution, the gravity level must to be less than 10-4.

An experimental study for the role of natural convection in the dissolution of GaSb into InSb melt, and the growth of InxGa1-xSb crystals

The article presents an experimental study for the role of convection occurring during the dissolution of GaSb into InSb melt, and the growth of InxGa1-xSb crystals. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of InxGa1-xSb crystal. Experiments were carried out for two different reference temperatures and two sample diameters. It was observed that the shape of the GaSb(seed)/InGaSb interface became flatter when the reference temperature was lower and the sample diameter was smaller. The growth length of uniform composition section was larger in the case of higher reference temperature. Experiments show that by varying the reference temperature and the sample diameter, the growth interface and the composition of the grown crystal can be controlled by controlling the natural convection in the melt.

Airplane and Drop Experiments on Crystallization of InxGa1−xSb Semiconductor under Different Gravity Conditions

Abstract : Melting and crystallization experiments of InGaSb were done under the reduced gravity condition (10(exp -2) G) in an airplane and at the normal gravity condition (lG) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature.