Heavy carbon atomic-layer doping at Si_{1 - x}Ge_x/Si heterointerface

Heavy C atomic-layer doping of about 10¹⁴ cm^{- 2} at the heterointerface between Si_{1 - x}Ge_x and Si using an ultraclean low-pressure chemical vapor deposition has been investigated. By heavy C atomic-layer doping at heterointerface between a Si cap layer and a Si_0.55Ge_0.45 layer in Si/Si_0.55Ge_0.45/Si(100) heterostructure, the intermixing between Si and Ge at heterointerface is effectively suppressed. For 4 nm thick Si_0.55Ge_0.45 cap layer/Si(100) heterostructure with C atomic-layer doping, Ge fraction of 0.45 and strain scarcely change with the heat treatment at 750 °C, while those without C atomic-layer doping are reduced. For 40 nm thick Si_0.55Ge_0.45 cap layer/Si(100) heterostructure, whose Si_0.55Ge_0.45 thickness is close to the critical thickness, it is found that the strained Si_0.55Ge_0.45 cap layer is relaxed by C atomic-layer doping at heterointerface. These results suggest that the heavy C atomic-layer doping suppresses strain relaxation as well as intermixing between Si and Ge at the Si_{1 - x}Ge_x/Si heterointerface especially for the heterostructure composed of nm-order thick films.