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

Arsenic-doped Si(001) layers with concentrations C_As up to 5×10¹⁸cm^-3 were grown on Si(001)2×1 at temperatures T_s=575-900°C by gas-source molecular-beam epitaxy (GS-MBE) using Si₂H₆ and AsH₃. This is almost an order of magnitude higher than the initially reported "maximum attainable" saturated C_As value for GS-MBE from hydride precursors. At constant J_AsH3/J_Si2H6. C_As decreases, while the film growth rate R_Si increases, with T_s. Temperature programmed desorption measurements show that As segregates strongly to the growth surface and that the observed decrease in C_As at high film growth temperatures is primarily due to increasingly rapid arsenic desorption from the segregated layer. Decreasing T_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 Si₂H₆ adsorption rate. At constant T_s, C_As increases, while R_Si decreases, with increasing J_AsH3/J_Si2H6. All incorporated As resides at substitutional electrically active sites for concentrations up to 3.8×10¹⁸cm^-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.