Quantum confinement effects in doped two-dimensional Si layers: Novel device design for two-dimensional pn-junction structures

We have experimentally studied the impurity dopant atom effects on band structure modulation (BSM) and phonon confinement effects (PCEs) in a two-dimensional (2D) Si layer. By the photoluminescence (PL) method, the effect of the dopant atom on the bandgap (EG) of 2D-Si is found to be very small. However, the EG narrowing effects of n+ 2D-Si are much smaller than those of conventional 3D n+-Si, which is characteristic of 2D-Si. On the other hand, Raman spectroscopy shows that the PCEs are completely independent of the phosphorous dopant density of n+ 2D-Si. Using the experimental BSM of 2D-Si, we introduce a device design for pn junction structures in 2D-Si for future complementary metal oxide semiconductor (CMOS) devices, to suppress the built-in potential increase of the pn junction, in spite of the EG expansion in the 2D-Si channel region.