Beta-SiC is a promising, wide bandgap material for high power electronic devices capable of operation at high temperatures. Its high saturation velocity, high breakdown electric field, and high thermal conductivity point to superior performance for high frequency applications. The successful fabrication of Beta-SiC devices requires high quality films to be epitaxially grown on lattice-matched substrate materials. Single crystals of Beta-SiC offer the optimum substrate material for lattice matching. The major problem to be overcome in the growth of large single crystals of Beta-SiC is polytype alpha-SiC formation. Cubic Beta-SiC crystallizes only below 2000 deg C. Above this temperature, SiC undergoes a phase transformation from the Beta-to the alpha-phase. In Phase I, we investigated two crystal growth techniques: sublimation and gas-vapor transport. We were able to grow small 3C-SiC crystals by both methods.

The report discusses the growth of beta silicon carbide by the hydrogen reduction of methyl trichlorine onto carbon substrates at 1500C. It is shown that alpha inclusions present are the rare 2H (Wurtzite) modification of silicon carbide and that their presence resulted from a vapor-liquid-solid growth mechanism which was dominated by impurities in the substrate. By carefully cleaning the substrate and purifying the methyltrichlorosilane, the alpha inclusions were eliminated. The 2H alpha crystals were then deliberately grown by introducing selected impurities locally on the substrate. Beta crystals were also intentionally grown by the vapor-liquid-solid technique by introducing appropriate impurities. Growth of beta silicon carbide from the melt is also briefly discussed. (Author).

Changes in crystal size and morphology were obtained by modifying the process for growing crystals of betasilicon carbide from solution in carbon-saturated melts. Well developed laths and plates were grown under conditions favoring dendritic growth mechanisms (low thermal gradient with moderate stirring). Polyhedral crystals grew under high thermal gradient conditions when high velocity stirring was employed. Three-dimensionaltype growth was also produced from a 73 wt percent ironsilicon alloy under conditions that normally produce lath-type growth. Uncorrected electron mobilities of 700 to 1000 sq cm/v-sec were measured at room temperature, and a few preliminary Hall measurements were made over the temperature range from 77 to 300 K. (Author).

Equipment and growth procedures for growing beta-silicon carbide epitaxially on beta-silicon carbide substrates from methyltrichlorosilane in a carrier gas of hydrogen is described. Hall and resistivity measurements and electron spin resonance measurements are discussed. The results show that the quality of the epitaxially grown material is comparable with that of the best solution grown crystals. Processing steps such as oxidation, masking, and etching have been performed and simple electroluminescent diodes have been fabricated. (Author).

Beta silicon carbide has the potential of becoming an important semiconductor device material for hazardous military environments such as high temperature and radiation. This report is concerned with a study of the growth of thin single crystal films of beta silicon carbide through molten metal intermediates. Thin films of nickel, cobalt, chromium and iron were deposited by vacuum deposition on to the (0001) faces of single crystals of alpha silicon carbide. Then heteroepitaxial layers of beta silicon carbide were deposited through the molten metal films by the hydrogen reduction of methyltrichlorosilane. The deposited films were studied by electron microscopy, electron diffraction and electron beam microprobe analysis to determine the growth mechanism and to arrive at optimum conditions for heteroepitaxial growth. From the results obtained it was concluded that nickel and cobalt were equally effective in promoting epitaxial growth. Films of nickel only 20A in thickness were as effective as those up to 300A. Results with chromium and iron were disappointing for different reasons. Chromium did not etch the substrate surface uniformly because of poor wetting. With iron, whisker growth of beta silicon carbide occurred at the surface. Although in many respects the growth of mechanism resembled that of the vapor-liquid-solid method, certain differences were observed which make the actual growth mechanism using nickel and cobalt films still uncertain. (Author).