Arsenic-doped Si(001) gas-source molecular-beam epitaxy: Growth kinetics and transport properties

Arsenic-doped Si(001) layers with concentrations C{sub As} up to 5{times}10{sup 18} cm{sup {minus}3} were grown on Si(001)2{times}1 at temperatures T{sub s}=575{endash}900{degree}C by gas-source molecular-beam epitaxy (GS-MBE) using Si{sub 2}H{sub 6} and AsH{sub 3}. This is almost an order of magnitude higher than the initially reported {open_quotes}maximum attainable{close_quotes} saturated C{sub As} value for GS-MBE from hydride precursors. At constant J{sub AsH{sub 3}}/J{sub Si{sub 2}H{sub 6}}, C{sub As} decreases, while the film growth rate R{sub Si} increases, with T{sub s}. Temperature programmed desorption measurements show that As segregates strongly to the growth surface and that the observed decrease in C{sub As} at high film growth temperatures is primarily due to increasingly rapid arsenic desorption from the segregated layer. Decreasing T{sub s} enhances As incorporation. However, it also results in lower film growth rates due to higher steady-state As surface coverages which, because of the lone-pair electrons associated with each As adatom, decrease the total dangling bond coverage and, hence, the Si{sub 2}H{sub 6} adsorption rate. At constant T{sub s}, C{sub As} increases, while R{sub Si} decreases, with increasing J{sub AsH{sub 3}}/J{sub Si{sub 2}H{sub 6}}. All incorporated As resides at substitutional electrically active sites for concentrations up to 3.8{times}10{sup 18} cm{sup {minus}3}, the highest value yet reported for Si(001):As growth from hydride source gases, and temperature-dependent electron mobilities are equal to those of the best bulk Si:As. {copyright} {ital 1999 American Institute of Physics.}