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GeSnC alloys offer a route to direct bandgap semiconductors for CMOS-compatible lasers, but the use of CBr4 as a carbon source was shown to reduce Sn incorporation by 83%–92%. We report on the role of thermally cracked H in increasing Sn incorporation by 6x–9.5x, restoring up to 71% of the lost Sn, and attribute this increase to removal of Br from the growth surface as HBr prior to formation of volatile groups such as SnBr4. Furthermore, as the H flux is increased, Rutherford backscattering spectroscopy reveals a monotonic increase in both Sn and carbon incorporation. X-ray diffraction reveals tensile-strained films that are pseudomorphic with the substrate. Raman spectroscopy suggests substitutional C incorporation; both x-ray photoelectron spectroscopy and Raman suggest a lack of graphitic carbon or its other phases. For the lowest growth temperatures, scanning transmission electron microscopy reveals nanovoids that may account for the low Sn substitutional fraction in those layers. Conversely, the sample grown at high temperatures displayed abrupt interfaces, notably devoid of any voids, tin, or carbon-rich clusters. Finally, the surface roughness decreases with increasing growth temperature. These results show that atomic hydrogen provides a highly promising route to increase both Sn and C to achieve a strongly direct bandgap for optical gain and active silicon photonics. 

The effect of precursor stoichiometry is reported on morphology, phase purity, and texture formation of polycrystalline diamond films. The diamond films were deposited on 100-mm Si (100) substrates using hot filament chemical vapor deposition at substrate temperature 720–750 °C using a mixture of methane and hydrogen. The gas mixture was varied with methane concentrations 1.5% to 4.5%. Diamond film thickness and average grain size both increase with increasing methane concentration. Diamond quality was checked using surface and cross-section by ultraviolet micro-Raman spectroscopy. The data show consistent diamond properties across the surface of the film and along the cross-section. XRD pole figure analyses of the films show that 3.0% methane results in preferential orientation of diamond in the〈111〉direction, whereas films deposited with 4.5% methane showed texture along the〈220〉direction in addition to〈111〉which was tilted ~ 23° with respect to the surface normal.