Horizontal Boat Research Articles

272 半導体用横型ボートにおける伝熱解析手法の検討

272 半導体用横型ボートにおける伝熱解析手法の検討

Defect segregation in CdGeAs2

Increased axial temperature gradients and growth rates have resulted in segregation of unwanted absorbing defects to the edges of CdGeAs2 single crystals produced by the horizontal gradient freeze technique. Long-wavelength infrared imaging of polished boules revealed a “clear” central core with absorption losses 26 times lower than in the darker edge regions. This pronounced segregation is attributed to the preferred incorporation of native defects at facets that form near the side walls of the horizontal boat. EPR, GDMS, and Hall effect analysis were used to characterize the nature of these defects.

Larvae and post-larvae of Penaeidae and Palaemonidae in coastal lagoons of the North of Rio de Janeiro (Macaé, RJ)

The northern part of the state of Rio de Janeiro shelters many coastal lagoons, located, mostly, in the "restinga" strip that stretches from the municipality of Macaé to the municipality of Quissamã. During 1995 and 1996 samplings were made aiming to verify the diversity and density of Natantia larvae in the Imboassica, Cabiúnas and Comprida lagoons. The monthly samples were taken with a 500 µ net, in horizontal drags from a boat. In Comprida lagoon no larvae of any family of these crustaceans were found. In Cabiúnas lagoon, the autumn was the season of the year with greatest relative abundance, the larvae belonging to only one genus: Macrobrachium. In Imboassica Lagoon samples were taken in two situations related to the variation of the water level and contact with sea water: horizontal boat dragging when the sandbar (the strip of sand that separates the lagoon from the sea) was closed, larvae of Macrobrachium sp. being found, and no seasonal variation being detected, and horizontal manual dragging with open and closed sandbar conditions, in a region close to the sandbar. With the sandbar open, larvae and post-larvae of Penaeus paulensis and P. brasiliensis were found, the greatest abundances being found in the months of April/96 and May/95.

Development of double ring heater halogen lamp furnace and melting/crystallization of BaB_2O_4 by horizontal boat method

Development of double ring heater halogen lamp furnace and melting/crystallization of BaB_2O_4 by horizontal boat method

New horizontal boat growth method of undoped, semi-insulating GaAs with low dislocation density

Undoped semi-insulating GaAs single crystals with up to 2 inch diameter and 400 mm length were grown by a horizontal boat growth method using a quartz ampoule, a PBN boat and a B 2O 3 encapsulant. A good quality crystal with an average dislocation density of less than 3 000 cm −2 was successfuly grown. The resistivity of an as-grown crystal ranged from 10 5 to 10 7 Ω cm, which could be increased up to 10 8 Ω cm through wafer annealing at 1150°C for 5 h under 1 atm arsenic gas pressure. These results indicate that the horizontal boat growth method has potential to provide low EPD, semi-insulating GaAs substrates for advanced electronic devices.

Liquid phase epitaxial growth of large area Hg1−xCdxTe epitaxial layers

The liquid phase epitaxial technique in a horizontal boat is used to grow large area epitaxial layers of Hg1−xCdxTe on CdTe substrates with x=1 to x=0.15. Areas as large as 25 cm2 have been grown from Te-rich melts that have excellent compositional uniformity (Δx=0.001–0.0028) and run-to-run reproducibility (Δx=0.003–0.004). Results are presented on surface morphology, compositional grading, and electrical properties. Histograms are presented showing run-to-run wavelength reproducibility and uniformity across the epilayers for both 10–15 and 20–25 cm2 areas for selected wavelengths with x≂0.3. Data are presented showing run-to-run uniformity of carrier concentration (4.5±0.66×1016 cm−3) and hole mobility (272±15 cm2/Vs) at 77 K for x≂0.3, including their dependence on wavelength.

LPE growth of GaAs submicron layers from supercooled solution: Layer thickness uniformity within a wafer

The thickness uniformity within a wafer is studied in GaAs LPE layers grown by the horizontal sliding boat techniques. Thickness nonuniformity appears in the sliding direction of a solution when very thin (∼0.3 μm thick) layers are grown from supercooled solutions. Thicker layers are grown on the side which is first brought into contact with the solution. The diffusion theory of LPE growth explains that such thickness distribution is mainly due to transient growth while a supercooled solution slides across the wafer.

Liquid Metal Flow in Horizontal Rods

The flow velocity and flow pattern of liquid tin contained in a long horizontal boat have been determined by radioactive tracer techniques. The major flow resulted from buoyancy forces generated by an imposed temperature gradient along the melt. The flow pattern in the longitudinal direction was observed to be unicellular. Flow in planes transverse to the longitudinal direction was also observed. A small adverse vertical temperature gradient was detected in the melt and is believed to be the driving force for the transverse flow. The results indicate that the flow velocity increases linearly with the average temperature gradient between the hot and cold ends of the melt, in the temperature range examined. The velocity is reproducible and is not particularly sensitive to slight variations in experimental procedure. The velocity is not dependent on the temperature distribution (linear or nonlinear) along the melt, providing there are no sections of the melt with a zero temperature gradient. In this case, fluid does not flow through these sections. The flow velocity increases with increasing average temperature of the melt. The results are in general agreement with the results predicted by a modification of Batchelor’s solution of fluid flow in a rectangular cavity. L. C. MacAULAY, Formerly a Graduate Student, Department of Metallurgy, University of British Columbia

Growth of InBi single crystals

Large single crystals (up to 20 cm length and 4 cm diameter) of InBi were grown by hard and soft mold Bridgman, Czochralski and horizontal boat techniques. The crystals were characterized in terms of subgrain mis-orientation and dislocation densities. Dislocation densities were determined by etching in a Br 2/methanol solution. Crystals of highest structural perfection with no observable subgrains and dislocation densities of 0.5−2×10 4/cm 2 were obtained by the Czochralski technique with seeds oriented along 〈 hk0〉 and pulling rates of 3–4cm/hour. Self-nucleated crystals grow rather exclusively with the c-axis perpendicular within 10 degrees to the growth direction.

Spectral analysis of temperature fluctuations in molten metals

Abstract Spectral analysis techniques have been used to obtain the power spectrum of the thermal fluctuations which were reported (Hurle 1966) to occur in molten gallium contained in a horizontal boat on which was impressed a large axial temperature gradient. The fluctuations have components which form a harmonic series, the fundamental of which has the frequency of the sinusoidal signal obtained at low temperature gradients. The results suggest that the fluctuations are due to the phenomenon of ‘overstability’, rather than to the onset of turbulence in the melt.

Avoidance of Growth-striae in Semiconductor and Metal Crystals grown by Zone-melting Techniques

IT has recently been shown1 that the growth striae found in semiconductor crystals grown by zone-melting techniques are caused by fluctuations in temperature in the melt from which the crystal is being grown. (The term growth-striae is used to describe a banded distribution of impurity revealed on etched crystal sections.) One of us has shown2 that the temperature fluctuations were a characteristic property of a liquid metal contained in a horizontal boat on which was impressed an axial temperature gradient. At lower temperature gradients, but still above some critical gradient, the temperature varied sinusoidally with time.

Elimination of Solute Banding in Indium Antimonide Crystals by Growth in a Magnetic Field

Samples of tellurium-doped indium antimonide that exhibited solute banding when solidified in a horizontal boat under ordinary conditions showed no bands when solidified in the presence of a vertical dc magnetic field. The effect of the field was to damp the thermal convection in the molten sample to the point of suppressing turbulence, thereby eliminating the temperature fluctuations in the liquid that cause the bands.

Temperature oscillations in molten metals and their relationship to growth striae in melt-grown crystals

Experiments are reported which show that the temperature distribution in molten gallium contained in a horizontal boat on which is impressed an axial temperature gradient becomes oscillatory when t...

Single Crystal Bismuth Telluride

Bismuth telluride has been investigated because of its promise as a material for thermo-electric applications. Attempts have been made to grow single crystals of the material by the Stockbarger method, by directional freezing in a horizontal boat, and by pulling from the melt. The first two methods were not found to be satisfactory because of segregation of tellurium towards the last end of the ingot to freeze. This was particularly marked at the slow speeds of withdrawal desirable for good single crystal growth. At fast speeds of withdrawal the segregation was prevented, but at these speeds large single crystals were not produced. Larger crystals, about 1 cm × 2 cm × 3 cm were produced by the pulling method, using a hydrogen atmosphere. These were all p-type of thermo-electric power 200-215μV deg-1 even when considerable departures from the stoichiometric composition Bi2Te3 were made in the charge from which the crystals were pulled. The energy gap of this material, measured optically, was 0.15 eV. A p-type single crystal specimen of thermo-electric power 200μV deg-1 had a room temperature electrical conductivity of 500 Ω-1 cm-1 parallel to the cleavage planes. The room temperature thermal conductivity of the same specimen was 0.0175 W cm-1 deg-1 parallel to the cleavage planes, and 0.0076 W cm-1 deg-1 perpendicular to the cleavage planes.