Epitaxial growth of P atomic layer doped Si film by alternate surface reactions of PH₃ and Si₂H₆ on strained Si _1-xGe_x/Si(1 0 0) in ultraclean low-pressure CVD

P atomic layer formation on Si_1-xGe_x(1 0 0) using PH₃ and subsequent Si epitaxial growth by ultraclean low-pressure CVD using Si₂H₆ have been investigated. The quantity of P atoms on Si_1-xGe_x(1 0 0) tends to increase and saturate with temperature, depending on Ge fraction in the range of 200-450 °C. By Si epitaxial growth on the P surface at 450 °C using Si₂H ₆ instead of SiH₄, heavy P doping with the P concentration over 3 × 10²¹ cm^-3 is achieved in an ultrathin region at the heterointerface with the thickness within 2 nm. For the P-doped samples, the Hall mobility of the electron is higher than that for uniformly P-doped Si with a lower P concentration of 10²⁰ cm^-3. From the mobility degradation after heat treatment up to 800 °C, it is expected that two-dimensional arrangement of P atoms is achieved for the as-deposited films.