Impurity doping effects on impurity band structure modulation in two-dimensional n super(+) and p super(+) Si layers for future CMOS devices

We experimentally studied the effects of n super(+) and p super(+) dopant atoms on the band structure modulation in two-dimensional (2D) Si layers for a wide range of dopant density N by the photoluminescence (PL) method. The bandgap E sub(G) of both n super(+) and p super(+) 2D-Si strongly depends on N, and decreases with increasing N, which is attributable to the E sub(G) narrowing effects delta E sub(G) even in 2D-Si. However, delta E sub(G) in the doped 2D-Si is much smaller than that in 3D-Si and depends on whether the dopant is donor or acceptor. We introduce a simple model for the small delta E sub(G), considering the impurity band structure modulation in heavily doped 2D-Si. As a result, we can estimate source/drain dopant density dependence of a built-in potential of pn junction in a 2D-Si layer for CMOS devices.