Atomically controlled processing for nitrogen doping of group IV semiconductors

The concept of atomically controlled processing for group IV semiconductors is based on atomic-order surface reaction control. On the atomic-order surface nitridation of Si_1-xGe_x by NH₃, N atoms bound to Ge atoms tend to be transferred to Si atoms during heat treatment. In the Si_0.5Ge_0.5 epitaxial layer, N doping dose of 6 × 10¹⁴ cm^-2 is confined within an about 1.5 nm thick region even after heat treatment at 650 °C. The N atoms in Si_1-xGe_x preferentially form Si-N bonds even at 400 °C. In the case of epitaxial Ge film, N atoms diffuse through nm-order thick Ge layer into Si_0.5Ge_0.5 layer on Si(100) substrate and form Si nitride even at 500 °C. Therefore, it is suggested that N diffusion in Ge layer is suppressed by the formation of Si nitride. These results open the way of atomically controlled processing for nitridation and N doping of group IV semiconductors.