Atomic-layer adsorption of P on Si(100) and Ge(100) by PH₃ using an ultraclean low-pressure chemical vapor deposition

Atomic-layer adsorption of P on Si(100) and Ge(100) at 200-750 °C by PH₃ was investigated using an ultraclean low-pressure chemical vapor deposition (CVD) system. At 300 °C, the PH₃ adsorption was suppressed on the H-terminated Si surface, but PH₃ was adsorbed dissociatively on the H-free Si surface with saturation tendency to subatomic layer. At 450-750 °C, the P atom concentration on the Si surface tended to saturate to about two or three atomic layers by exposing PH₃ with little influence of the carrier gas (H₂ or He). When the P-adsorbed Si was kept in Ar and in H₂ at 650 °C after PH₃ exposure, the P atom concentration decreased to about one atomic layer by thermal desorption and also by reduction due to hydrogen. On the Ge surface, PH₃ adsorption was suppressed by H-termination at 200 °C, P atom concentration saturated to the single atomic layer at 300-450 °C. Furthermore, P desorption from the Ge surface at 450 °C occurred much faster than that from the Si surface at 650 °C, while P bonded to Ge was stable at 300 °C.