A precursor, neopentasilane, is used to produce high-quality silicon epitaxy by chemical vapor deposition under 700 °C with very high growth rates. Low background dopant concentration and excellent crystal quality were determined from secondary-ion-mass spectroscopy and cross sectional transmission electron microscopy. Growth rates as high as 130 nm/min at 600 °C have been achieved. Growth rates in nitrogen and hydrogen ambients are about equal for neopentasilane, unlike those for growth with low-order silanes. A concerted reaction, where an open site is generated at the same time the adatom is adsorbed, is proposed as a possible mechanism for both the high growth rate with neopentasilane as well as the similar rate with hydrogen and nitrogen carriers.