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

Abstract

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.