SiGeC: Band gaps, band offsets, optical properties, and potential applications

Studying the structural and photoluminescence properties of pseudomorphic Si1−yCy and Si1−x−yGexCy multiple quantum well (QW) structures on (001) Si substrates offer a quantitative characterization of the band gap and band offset shifts caused by C alloying for y<3%. The main features of Si1−yCy alloys, which are a reduced lattice constant and a strong lowering of the conduction band energy, promise that C may serve as a counterpart to Ge in Si heteroepitaxy. The photoluminescent properties of Si1−yCy and SiGeC QWs are comparable to SiGe. Novel pseudomorphic Si1−yCy/SiGe coupled QW structures and Si1−yCy/Ge quantum dot structures result in a strong enhancement of the photoluminescent efficiency. The ternary SiGeC material system offers a higher degree of freedom in strain and band edge engineering of structures. We focus on our recent results on Si1−yCy and SiGeC QW layers embedded in Si concerning the growth by solid-source molecular beam epitaxy, structural properties, thermal stability, optical properties, and band offsets. The prospects of SiGeC alloys for realization of optoelectronic structures are discussed. First characteristics from 0.75 μm p-channel modulation-doped field-effect transistor devices containing an active SiGeC layer demonstrate good electrical properties.