Experimental study on interface region of two-dimensional Si layers by forming gas annealing

Abstract

We experimentally studied the SiO2/Si and Si/buried oxide (BOX) interface regions of a two-dimensional (2D) Si layer, by forming gas annealing (FGA). A photoluminescence (PL) result measured at various lattice temperature, TL, values shows that the PL intensity IPL of the 2D-Si layer rapidly increases and then saturates with increasing FGA temperature, TA, and time, tA. IPL also increases with decreasing TL. A one-dimensional (1D) Schroedinger equation simulator indicates that some of the electrons in the 2D-Si layer generated by a PL excitation laser are quantum–mechanically transmitted into Si interface regions. Actually, we experimentally confirmed that the PL spectra of the 2D-Si layer can be fitted by the PL emission from two regions with different PL peak photon energy values, EPH, which consist of a typical 2D-Si and the interface regions of both the surface SiO2/Si and Si/BOX. Thus, this forming gas dependence is probably attributable to the improved lifetime τ of electrons in the surface interface region, because the Si surface is terminated by H atoms. Moreover, the EPH of the interface region is higher than that of the 2D-Si layer, because of the graded increased bandgap in the interface regions. However, the EPH of 2D-Si is independent of both TA and TL, and this TL independence does not agree with that of a 3D-Si layer. Consequently, we experimentally verified the larger impact of the Si interface on the performance of 2D-Si layer.