Direct Optical Measurement of the valence band offset of p + Si 1−x−y Ge x C y /p − Si (100) by Heterojunction Internal Photoemission

Optical absorption measurements have been performed to study the effect of carbon on the valence band offset of compressively strained p + Si 1−x−y Ge x C y /(100) p − Si heterojunction internal photoemission structures grown by Rapid Thermal Chemical Vapor Deposition (RTCVD) with substitutional carbon levels up to 2.5%. Results indicated that carbon decreased the valence band offset by 26 ± 1 meV/ %C. Results from optical measurement in this study agreed with previous data from capacitance-voltage measurements. Based on previous reports of carbon effect on the bandgap of compressively strained Si 1−x−y Ge x C y , our work suggests that the effect of carbon incorporation on the band alignment of Si 1−x−y Ge x C y /Si is to reduce the valence band offset, with a negligible effect on the conduction band alignment.