Silicon epitaxy onto silicon wafers above 600\r{ }C by 100 nm/min hot-wire chemical vapor deposition*

We study a new silicon epitaxy regime by hot-wire chemical deposition onto silicon surfaces above 600\r{ }C. In this regime, epitaxy proceeds at high growth rates ($>$100 nm/min) compared with lower-T growth, and does not appear to be thickness-limited. With a tantalum hot-wire operating at 1900\r{ }C in SiH$_{4}$, we obtain phase-pure Si at 77 nm/min on (100)-oriented wafers at 650\r{ }C. With a tungsten filament at 2100 \r{ }C, phase-pure epitaxy proceeds faster than 100 nm/min from 620 to 700\r{ }C. Epitaxial growth up to 11{\-}$\mu $m thick is confirmed by transmission electron microscopy, x-ray diffraction and in-situ ellipsometry. This relatively low T epitaxial growth regime could be utilized for photovoltaic devices made by epitaxial thickening of c-Si seeds on low-cost substrate such as borosilicate glass. Temperature above 600$^{o}$C and corresponding thermal dehydrogenation of the growing surface is critical for the high-quality, rapid epitaxial growth: between 450 and 600\r{ }C, there appears to be an intermediate region where epitaxy is poor or nonexistent -- even in comparison with epitaxy at 200 to 400\r{ }C. The role of gas depletion chemistry, as well as structural/electronic quality is discussed.