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We have investigated the formation of the locally strained Ge nanostructure with epitaxial Ge1-xSnx stressors and characterized the microscopic strain field in the Ge1-xSnx/Ge fineheterostructures by synchrotron X-ray microdiffraction and finite element method (FEM) calculations. We achieved local epitaxial growth of Ge1-xSnx with Sn contents of 2.9% and 6.5%, sandwiching the 25 nm-wide Ge fine line structure. Microdiffraction measurements revealed that out-of-plane tensile strain induced in the Ge line effectively increased with decreasing Ge width and increasing Sn content of Ge1-xSnx stressors, which is in good agreement with FEM calculations. An out-of-plane tensile strain of 0.8% along the Ge[001] direction is induced in a 25 nmwide Ge line, which corresponds to an in-plane uniaxial compressive strain of 1.4% in the Ge line sandwiched between Ge0.935Sn0.065 stressors. [ABSTRACT FROM AUTHOR]

The electrical and optical material properties of epitaxial Ge1−xSnx and SiyGe1−x−ySnx are of high interest for novel device applications. However, the limited Sn solubility in Ge makes the epitaxial growth of Ge1−xSnx and SiyGe1−x−ySnx challenging. Most of the literature describing the epitaxial growth is for Ge2H6 and SnCl4 as Ge and Sn precursors, respectively. A more recent publication deals with the epitaxial growth of high-quality Ge1−xSnx with the more conventional GeH4. In this manuscript, we compare the structural and optical material quality of Ge1−xSnx, epitaxially grown on Ge virtual substrates as a function of growth pressure, growth temperature, the choice of the carrier gas (H2 or N2) and the choice of the Ge precursor (GeH4 versus Ge2H6). The best material quality in terms of surface morphology and photoluminescence characteristics is obtained if GeH4 is used as a Ge precursor. For Ge1−xSnx grown with Ge2H6 and at atmospheric pressure, pyramidical defects can be seen and there is a risk for uncontrolled local Sn agglomeration. The pyramidical defects are not observed on Ge1−xSnx layers grown at reduced pressure, but the highest achievable substitutional Sn concentration is lower. No pyramidical defects are found for Ge1−xSnx layers grown with GeH4 and the issue of uncontrolled local Sn agglomeration does not appear. [ABSTRACT FROM AUTHOR]

We report the metal-organic chemical vapor deposition method for epitaxy of n+-Ge and Ge1−xSnx layer with an electron concentration as high as 2 × 1019 cm−3 by in situ phosphorus (P) doping. In this study, we examined MO precursors of tertiary-butyl-germane (t-BGe), tri-butyl-vinyl-tin (TBVSn), and two kinds of P precursors of tri-ethyl-phosphine (TEP) and tertiary-butyl-phosphine (t-BP). We have investigated crystalline and electrical characteristics of P-doped Ge and Ge1−xSnx layers. In the case of using TEP, the P-doped Ge0.98Sn0.02 epitaxial layer grown at 320 °C on virtual Ge substrate was demonstrated, in which the chemical P-incorporation as high as 1 × 1019 cm−3 and the full electrical activation of P. By using t-BP instead of TEP, the chemical P-incorporation as high as 8.1 × 1019 cm−3 was achieved for Ge epitaxial layer grown at 300 °C. It is found that the activation energy of the growth rate of Ge and P with t-BGe, TEP, and t-BP was estimated to be 1.0−1.2, 2.1, and 1.1 eV, respectively. The precursor combination of t-BGe and t-BP has a wider temperature window for a lower growth temperature. In situ P-doping with t-BP enables us to grow the Ge0.975Sn0.025 epitaxial layer with an electron concentration as high as 1.7 × 1019 cm−3 at the temperature as low as 300 °C. For both cases of TEP and t-BP, we observed that increasing Sn content significantly reduces the P-incorporation, which is not common phenomenon in a conventional CVD growth. [ABSTRACT FROM AUTHOR]

We have investigated the structural and electrical properties of n-type doped Si1−xGex epitaxial layers (x = 24–26%) grown by chemical vapor deposition with conventional [SiH2Cl2 (DCS)/GeH4] and high-order (Si2H6/Ge2H6) precursor combinations. X-ray diffraction, atomic force microscopy, and deep-level transient spectroscopy (DLTS) measurements were performed for characterization. The crystalline properties and surface morphology of the Si1−xGex layer with Si2H6/Ge2H6 grown at temperatures as low as 550 °C show good structural quality similar to that with DCS/GeH4 grown at 615 °C. On the other hand, in terms of electrical properties, the DLTS measurement reveals the existence of vacancy-related complexes in the as-grown layer with Si2H6/Ge2H6. We found that post-deposition annealing at 200 °C for the Si1−xGex epitaxial layer is effective for annihilating vacancy-related defects with densities down to as low as that of conventional precursors. [ABSTRACT FROM AUTHOR]