Growth and strain compensation effects in the ternary Si1−x−yGexCy alloy system

Abstract

Strain compensation is an important aspect of heterostructure engineering. In this letter, we discuss the synthesis of pseudomorphic Si1−yCy and Si1−x−yGexCy alloy layers on a silicon (100) substrate by molecular beam epitaxy using solid sources and the controlled strain compensation that results from the introduction of the ternary system. The introduction of C into substitutional sites in the crystal lattice is kinetically stabilized by low-temperature growth conditions (400–550 °C) against thermodynamically favored silicon-carbide phases. The lattice constant in Ge is about 4% larger than in Si, whereas in diamond it is 52% smaller. Consequently, the compressive strain caused by 10.8% Ge in a pseudomorphic Si1−xGex alloy can be compensated by adding about 1% carbon into substitutional lattice sites of the film assuming Vegard’s law of linear change of the lattice constant in the alloy as a function of the composition. Using x-ray diffraction, we observe a partial strain compensation in Si0.75−yGe0.25Cy alloys on Si depending on the amount of carbon in the layer, with no observable misfit dislocation generation. The Raman spectra from Si1−yCy and Si1−x−yGexCy alloys show a substitutional carbon vibration mode at about 600 wavenumbers. No indication of silicon-carbide precipitation is observed in transmission electron microscopy and Raman spectroscopy.

Raman and Fourier transform infrared study of substitutional carbon incorporation in rapid thermal chemical vapor deposited Si1−x−yGexCy on (1 0 0) Si

“…This enables band engineering via strain control in group IV semiconductors. 1,2 As shown recently, the addition of modest amounts of substitutional carbon into Si 1−x Ge x reduces the strain originating from the lattice mismatch between SiGe and Si and provides an additional design parameter in manipulating electronic properties. 3,4 The presence of carbon in the SiGeC lattice induces a very large local bond distortion, resulting in a significant change in the phonon frequencies.…”

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

“…Recently, impressive progress has been made in the growth and characterization of Si 1ϪxϪy Ge x C y alloys. [1][2][3][4][5] Si 1ϪxϪy Ge x C y offers considerably greater flexibility, compared to that available in the Si/Si 1Ϫx Ge x material system, to control strain and electronic properties in Group IV heterostructures, and leads to the possibility of fabricating Group IV heterostructure devices lattice matched to Si. [1][2][3][4][5][6] Effective design, fabrication, and characterization of such devices, however, requires the accurate measurement of the energy band offsets in Si/Si 1ϪxϪy Ge x C y heterojunctions.…”

SiGeC alloy layer formation by high-dose C+ implantations into pseudomorphic metastable Ge0.08Si0.92 on Si(100)

“…This may convert the strain state from compressive to tensile in the GeSi film. [5][6][7][8][9] Backscattering/channeling spectra for implanted samples, after implantation at room temperature and after annealing, are shown in Fig. 2͑a͒.…”

“…11 Si 1ϪxϪy Ge x C y alloy layers have shown less compressive strain than Ge x Si 1Ϫx alloy layers due to the strain compensation or shown rather tensile strain depending on the C and Ge composition in the layers. [5][6][7][8] Because the main effect of substitutionally incorporated carbon in the strained GeSi layers is strain compensation, it is expected that thick SiGeC layers can be grown without generation of misfit or threading dislocations. However, the complete substitutionality of C is not easy to achieve in all methods of epitaxial growth due to the low solubility of C in Si, and the tendency of carbon to form silicon carbide, or C-C bonds.…”

“…[1][2][3][4] Recently, for the same potential benefits, Si 1ϪxϪy Ge x C y alloy layers have been epitaxially grown by molecular-beam epitaxy, 5,6 chemical-vapor deposition, 7,8 or by solid-phase epitaxial annealing following high-dose implantation. 9,10 Valence band offset or conduction band offset in the SiGeC layers has also been investigated and reported.…”