Different charging behaviors between electrons and holes in Si nanocrystals embedded in SiN_x matrix by the influence of near-interface oxide traps

Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals (Si-NCs) embedded in SiN_x floating gate MOS structures. The capacitance-voltage (C-V), current-voltage (I-V), and admittance-voltage (G-V) measurements are used to investigate the charging characteristics. It is found that the maximum flat band voltage shift (ΔV_FB) due to full charged holes (～ 6.2 V) is much larger than that due to full charged electrons (～ 1 V). The charging displacement current peaks of electrons and holes can be also observed by the I-V measurements, respectively. From the G-V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the SiO₂/Si-substrate interface. Combining the results of C-V and G-V measurements, we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism. The evolution of G-V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.