Carbon-induced trapping levels in oxide dielectrics

Abstract

Carbon impurities are easily unintentionally incorporated into oxide dielectrics during growth. Carbon substituting on the cation site in these oxides leads to carrier-trapping levels within the band gap, which are detrimental for metal-oxide-semiconductor transistors. Here, the authors examine the role of C impurities in a range of wide-band-gap oxide dielectrics. The authors find that though the electrical character of the Ccation center depends on the valence of the host cation, these centers lead to charge-state transition levels that all fall roughly −3.5 eV below the vacuum level when the band structures of the dielectrics are put on an absolute energy scale. This level lies near the conduction-band minima of channel materials such as GaN, Si, and GaAs, indicating that C impurities may be a common source of carrier-trapping in oxide dielectrics.