Comparative Study of Charge Trapping in High-Dose Si and Ge-Implanted Al/SiO2/Si Structures

We have studied the trapping of negative and positive charge in Si-implanted SiO2 layers of Al/SiO2/Si-based devices during high-field electron injection from the Si substrate under conditions typically used for obtaining electroluminescence. The location, capture cross-section and concentration of negatively and positively charged traps have been determined in dependence on the time of heat treatment by rapid thermal annealing (RTA). A comparison between the results obtained from Si- and Ge-implanted oxide layers has been made. It has been shown that in the case of Si-rich oxides an increase in the RTA time leads to the formation of hole and electron traps of high concentration, both of which are located within the oxide. For Ge-rich oxide layers, however, the hole traps are found primarily in the vicinity of the SiO2/Si interface while the electron traps are present within the oxide. The nature of these traps has been discussed.