ELECTRONIC-PROPERTIES OF SI SI1-X-YGEXCY HETEROJUNCTIONS/

We have used, admittance spectroscopy and deep-level transient spectro scopy to characterize electronic properties of Si/Si1-x-yGexCy heteros tructures. Band offsets measured by admittance spectroscopy for compre ssively strained Si/Si1-x-yGexCy heterojunctions indicate that incorpo ration of C into Si1-x-yGexCy lowers both the valence- and conduction- band edges compared to those in Si1-xGex by an average of 107+/-6meV/% C and 75+/-6meV/%C, respectively. Combining these measurements indicat es that the band alignment is type I for the compositions we have stud ied, and that these results are consistent with previously reported re sults on the energy bandgap of Si(1-x-y)Ge(x)C(y )and with measurement s of conduction band offsets in Si/Si1-yCy heterojunctions. Several el ectron traps were observed using deep-level transient spectroscopy on two n-type heterostructures. Despite the presence of a significant amo unt of nonsubstitutional C (0.29-1.6 at. %), none of the peaks appear attributable to previously reported interstitial C levels. Possible so urces for these levels are discussed. (C) 1998 American Vacuum Society .