We have grown compositionally graded GexSi1−x layers on Si at 900 °C with both molecular beam epitaxy and rapid thermal chemical vapor deposition techniques. Triple-crystal x-ray diffraction reveals that for 0.10<x<0.53, the layers are totally relaxed. GexSi1−x cap layers grown on these graded layers are threading-dislocation-free when examined with conventional plan-view and cross-sectional transmission electron microscopy. Electron beam induced current images were used to count the low threading dislocation densities, which were 4×105±5×104 cm−2 and 3×106±2×106 cm−2 Eq. 2×106 cm−2 for x=0.23 and x=0.50, respectively. Photoluminescence spectra from the cap layers are identical to photoluminescence from bulk GexSi1−x.

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Articles you may be interested inAnalysis of electronic structure of amorphous InGaZnO/SiO2 interface by angle-resolved X-ray photoelectron spectroscopy Angle-resolved x-ray photoelectron spectroscopy ͑AR-XPS͒ is utilized in this work to accurately and nondestructively determine the nitrogen concentration and profile in ultrathin SiO x N y films. With furnace growth at 800-850°C using nitric oxide ͑NO͒ and oxygen, 10 13 -10 15 cm Ϫ2 of nitrogen is incorporated in the ultrathin (р4 nm͒ oxide films. Additional nitrogen can be incorporated by low energy ion ( 15 N 2 ) implantation. The nitrogen profile and nitrogen chemical bonding states are analyzed as a function of the depth to understand the distribution of nitrogen incorporation during the SiO x N y thermal growth process. AR-XPS is shown to yield accurate nitrogen profiles that agree well with both medium energy ion scattering and secondary ion mass spectrometry analysis. Preferential nitrogen accumulation near the SiO x N y /Si interface is observed with a NO annealing, and nitrogen is shown to bond to both silicon and oxygen in multiple distinct chemical states, whose thermal stability bears implications on the reliability of nitrogen containing SiO 2 .

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A modulation-doped Si/GexSi1−x structure was fabricated in which a thin Si layer is employed as the conduction channel for the two-dimensional electron gas. The strained heterostructure is fabricated on top of a low threading dislocation density, totally relaxed, GexSi1−x buffer layer with a linearly graded Ge concentration profile. The mobility of the two-dimensional electron gas as determined from Hall measurements was 1600 cm2/V s at 300 K and 96 000 cm2/V s at 4.2 K. Recently, a 4.2 K mobility of 125 000 cm2/V s was observed from a similar sample.