Characterization of traps in SiGe:C channel heterojunction PMOSFETs

In this work, inelastic tunneling spectroscopy (IETS) of SiGe:C channel heterojunction PMOSFETs has been used to study the modes of vibrations (due to molecular species and phonons) present in the tunneling junctions and also to characterize the traps responsible for trapping/de-trapping of channel carriers. Peaks observed in the second derivative spectra of the drain-current provided information for identification of various traps and defects in the metal-insulatorsemiconductor (MIS) structures for thin tunneling oxide present in the SiGe:C PMOSFETs. Both the optical and acoustic phonons are observed for SiGe, SiO2 and Si-C. From the spectra obtained by varying gate voltage between 180-350 mV (in both forward and reverse bias), the trapping/de-trapping process has been observed which comprises of charge trapping and trap-assisted conduction phenomena. The traps that take part in the trapping of carriers are also identified from the results.

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