Band offsets in Si/Si1-x-yGexCy heterojunctions measured by admittance spectroscopy

We have used admittance spectroscopy to measure conduction-band and valence-band offsets in Si/Si1-xGex and Si/Si1-x-yGexCy heterostructures grown by solid-source molecular-beam epitaxy. Valence-band offsets measured for Si/Si1-xGex heterojunctions were in excellent agreement with previously reported values. Incorporation of C into Si1-x-yGexCy lowers the valence- and conduction-band-edge energies compared to those in Si1-xGex with the same Ge concentration. Comparison of our measured band offsets with previously reported measurements of energy band gaps in Si1-x-yGexCy and Si1-yCy alloy layers indicate that the band alignment is Type I for the compositions we have studied and that our measured band offsets are in quantitative agreement with these previously reported results. (C) 1997 American Institute of Physics.