Impact of Si cap layer growth on surface segregation of P incorporated by atomic layer doping

In atomic layer doping of P using an ultraclean low-pressure chemical vapor deposition (CVD), the relationship between surface segregation of P during Si cap layer growth at 450 °C with Si₂H₆ partial pressure of 3-20 Pa on P atomic layer formed on Si_0.3Ge_0.7/Si(100) and the incorporated P amount at initial position has been investigated. For higher Si₂H₆ partial pressure and for the initial P atom amount of P atomic layer below about 4 × 10¹⁴ cm^{- 2}, the incorporated P atoms are almost confined within the 1 nm region around the heterostructure interface. The P amount is nearly the same as the initial one. For initial P atom amount higher than 4 × 10¹⁴ cm^{- 2}, P segregation on surface is enhanced, and the incorporated P atom amount around the heterointerface tends to saturate to maximum value of about 4 × 10¹⁴ cm^{- 2}. This maximum value decreases with decreasing Si₂H₆ partial pressure. These results suggest that the number of site at the heterointerface between Si cap layer and Si_0.3Ge_0.7 layer, in which P atoms are incorporated, is about 4 × 10¹⁴ cm^{- 2} and in the case of low Si₂H₆ surface coverage, the incorporated P atom amount at the heterointerface decreases due to surface segregation.