Boron diffusion rate

Solubility with temperature data for nitrogen, aluminium, boron, gallium and phosphorus, on both Si and C faces, and maximum solubilities for a wider range of impurities at temperatures >2500°C in 6H-SiC have been detailed. No data for other polytypes are available. Diffusion rates of impurities in SiC are very slow (for temperatures between 1800 and 2300 °C) whether for those species, such as boron and nitrogen, which migrate via Si/C vacancies or for those, such as beryllium, lithium and hydrogen, which diffuse interstitially. Some impurities show 2-component diffusion profiles. 

The diffusion rate increases with decreasing polytype hexagonality in the row 4H, 15R, 6H, 21R, 8H, 3C (Fig. 10). All the characteristics described are in good agreement with the vacancy diffusion model referring to boron atom-carbon vacancy complexes. 

Once the silicon disc is cleaned, the first step is diffuse ions into either side of the silieon disc to first form either the p-layer or the n-layer. Some manufacturers like to have the n-layer closer to the light source, as shown in the above diagram, while others prefer the opposite. At any rate, ions like and are generally used to form the active electrical layers. A number of differing processes have been developed to do this, the exact nature of which depending upon the speeific manufacturer of solar cells. Sputtering, vapor-phase and evaporation are used. The most common process uses a volatile boron or phosphorous compound to contact the surface. 

As shown in Table 10.5, non-metaUic fuels used as ingredients of pyrolants are boron, carbon, silicon, phosphorus, and sulfur. Similarly to metal particles, non-metal particles are oxidized at their surfaces. The processes of diffusion of oxidizer fragments to the surface of a particle and the removal of oxidized fragments therefrom are the rate-controlling steps for combustion. 

Pilot plant studies (flow rates, 1 cm/s) with the SB-1 anion exchange resin (column diameter, 0.3-0.7 cm) yielded distribution coefficients of the order D = 400 cmVg. The boron sorption process was shown to be film diffusion controlled. The equilibrium values of boron loading were reached in 6-8 hr [280]. Boron elution and resin regeneration were carried out with 0.1 M NaOH. The complete elution of boron required 10 column volumes at 10 BV and yielded concentrates of 100 mg/L. This facilitated the eventual reduction to solid concentrates of alkali metal borates [281]. 

The occurrence of etch rate reduction on highly boron doped materials appears to be independent of doping methods, whether by solid-source diffusion, epitaxial growth, or ion implantation. However, the boron concentration at which significant reduction occurs is different for different methods of doping. The critical boron concentration for etch rate reduction to occur is affected by the defect density in different doped materials. It is found that for similar boron concentrations the amount of etch rate reduction in KOH solutions decreases with increasing defect densityIn... 

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