Shigehiro Nishino

Epitaxial growth and electric characteristics of cubic SiC on silicon

Single crystals of cubic SiC were heteroepitaxially grown by chemical vapor deposition (CVD) using a SiH4‐C3H8‐H2 system on silicon substrates. To reduce the large lattice mismatch between cubic SiC and silicon, a buffer layer was made by carbonizing the surface of a Si substrate in the CVD system. An optimum condition for the buffer layer formation was determined by x‐ray rocking curve measurements, reflection electron diffraction, and Auger electron spectroscopy. Electrical properties of the epitaxial cubic SiC layer were measured, and the mobilities on the Si(111) substrate were found to be larger than those on the Si(100) substrate. Diode characteristics of epitaxially grown p‐n junctions were also investigated.

Antiphase‐domain‐free growth of cubic SiC on Si(100)

Single crystals of cubic SiC that are free of antiphase domains were successfully grown by chemical vapor deposition on Si substrates inclined at 2° from (100) towards (011). The relationship between the generation of antiphase domains and the inclination of a surface was investigated by using spherically polished Si substrates. Inclination, except towards (011), resulted in the generation of antiphase domains. Elimination of antiphase domains was confirmed by molten KOH etching of the grown layer.

Growth and morphology of 6H-SiC epitaxial layers by CVD

Abstract Single crystals of 6H-SiC were epitaxially grown on 6H-SiC substrates in the temperature range of 1500 to 1750°C with gas composition: H 2 ≈ 1 l/min, SiCl 4 ≈ 1 ml/min, C 3 H 8 ≈ 0.05 ml/min. The grown layers were transparent and mirror-like. The morphology of the grown layer was strongly influenced by the polarity of the substrate surface. Aggregates of trapezoidal crystals were observed on the (000 1 )C surface and a mosaic pattern was observed on the (0001)Si surface. By observing the initial stage of the crystal growth, the growth mechanism of 6H-SiC is discussed. On (000 1 )C surfaces the vertical growth dominates, while on (0001)Si surfaces the lateral growth dominates.

Heteroepitaxial growth of β-SiC on silicon substrate using SiCl4-C3H8-H2 system

Abstract Single crystals of β-SiC were prepared on Si substrates at a temperature around 1390°C with the standard conditions: H 2 ≈ 1 1/min, SiCl 4 ≈3 ml/min, C 3 H 8 ≈1 ml/min, deposition period≈10 min. The dependences of the growth rate and the crystallinity on the substrate temperature were studied. By detailed reflection electron diffraction analyses, the crystallinity of β-SiC with 1 μm thickness was found to be better for the layer on the (100) and (110)Si substrates than for that on the (111)Si substrate. An activation energy of 25kcal/mole was obtained for the formation of β-SiC. Optimum conditions to obtain thicker β-SiC films are discussed.

Single crystal growth of hexagonal SiC on cubic SiC by intentional polytype control

Crystal growth of SiC on 3C-SiC(100) substrates has been carried out by using a sublimation method, utilizing the phase transformation from cubic 3C-SiC to hexagonal 6H-SiC at high temperatures. Polytype control in SiC growth on CVD-grown 3C-SiC(100) substrates was successfully achieved for the first time. The growth rate was several hundred microns per hour. The polytypes and crystallographic planes of the grown layers were examined using photoluminescence, Raman spectroscopy, X-ray diffraction and RHEED analyses. The polytypes of the grown layers change from cubic 3C modification to hexagonal 6H modification with increase in temperature. 6H-SiC with (0114) planes can be grown on 3C-SiC(100). Ingots of 6H-SiC up to 15 mm in diameter and 6 mm in length were grown in 6 h. The grown mechanism of 6H-SiC on 3C-SiC substrates based on the experimental results is discussed.

Epitaxial growth of α-SiC layers by chemical vapor deposition technique

Single crystals of α-SiC were grown on α-SiC substrates at a temperature between 1570 and 1630° with the standard gas flow rate: H2 ˜ 1 liter/min, SiCl4 ˜ 1.7 ml/min and C3H8 ˜ 0.1 ml/min. The grown layers were transparent greenish-blue, and surfaces were mirror-like. By an X-ray back-reflection Laue pattern and a reflection electron diffraction method, the grown layer was identified as 6H-SiC, one polytype of α-SiC. Crystal growth was influenced by substrate temperature, flow rates of reaction gases and the surface polarity of the substrate. The growth rate decreased with increase of the substrate temperature in the above temperature region. A lamellar structure was observed on the (0001)Si surface and a mosaic structure was observed on the (0001)C surface. The mole ratios of both SiCl4 and C3H8 to H2 and that of Si to C had some influence on crystal growth. Undoped layers were n-type due to nitrogen. P-type SiC was grown by doping Al during crystal growth. Doping effects were studied by photoluminescence and electrical measurements.

Low-vacuum metalorganic vapor phase epitaxy of InGaP and its immiscible growth

Abstract InP and InGaP crystal growth on GaAs(100) was carried out by low-vacuum (0.03 Torr) MOVPE. Single crystals of InGaP were obtained on GaAs when the substrate temperature was 670°C. In this low-vacuum MOVPE growth of InGaP, as in conventional MOVPE, the growth rate is limited by the supply of group-III metalorganics, and Ga-element is taken into the grown layer more effectively than In-element. In some cases, immiscible InGaP growth was observed as a compositional separation in the grown layers when the substrate temperature was below 620°C. A model for the crystal growth in low-vacuum MOVPE, which can explain the occurence of the immiscibility, is proposed.

Immiscible growth of In1−xGaxP in low-vacuum MOVPE

A new type of immiscible growth of In1−xGaxP on GaAs was observed in low-vacuum (0.03 Torr) MOVPE. From the compositional separation observed as two separated peaks of (200) in an X-ray diffraction pattern, the surface morphology of the immiscible In1−xGaxP layer, and an analysis for the distribution of In and Ga by EPMA, it was found that InP-rich crystallites were formed in a GaP-rich flat layer. To explain the immiscible growth of In1−xGaxP in low-vacuum MOVPE, a growth model was constructed based on a modification of a thermodynamic explanation of immiscibility. By this model, three types of the crystal growth (immiscible In1−xGaxP, normal In1−xGaxP and InP growth on GaAs) were explained, consistently with surface morpologies.