Electronic properties of Si/Si1–x–yGexCy heterojunctions
Abstract
We have used admittance spectroscopy and deep-level transient spectroscopy to characterize electronic properties of Si/Si1–x–yGexCy heterostructures. Band offsets measured by admittance spectroscopy for compressively strained Si/Si1–x–yGexCy heterojunctions indicate that incorporation 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 ± 6 meV/% C and 75 ± 6 meV/% C, respectively. Combining these measurements indicates that the band alignment is type I for the compositions we have studied, and that these results are consistent with previously reported results on the energy band gap of Si1–x–yGexCy and with measurements of conduction band offsets in Si/Si1–yCy heterojunctions. Several electron traps were observed using deep-level transient spectroscopy on two n-type heterostructures. Despite the presence of a significant amount of nonsubstitutional C (0.29–1.6 at. %), none of the peaks appear attributable to previously reported interstitial C levels. Possible sources for these levels are discussed.
Additional Information
©1998 American Vacuum Society. (Received 10 November 1997; accepted 2 March 1998) The authors would like to thank M. Robinson, J.E. Huffman, and R. Westhoff at Lawrence Semiconductor Research Laboratory for growth of the CVD samples. The authors would like to acknowledge support from DARPA MDA972-95-3-0047 for work at UCSD, HRL, ASU, and LSRL and from ONR Grant No. N00014-95-1-0996 for work at UCSD. E.T.Y. would like to acknowledge receipt of a Sloan Research Fellowship. B.L.S. and E.T.Y. would also like to thank S.S. Lau for access to part of the equipment used in this work.Files
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