Matthew Bauer

Synthesis of ternary SiGeSn semiconductors on Si(100) via SnxGe1−x buffer layers

Single-phase Si1−x−yGexSny alloys with random diamond cubic structures are created on Si(100) via ultrahigh vacuum chemical vapor deposition reactions of SnD4 with SiH3GeH3 at 350 °C. Commensurate heteroepitaxy is facilitated by Ge1−xSnx buffer layers, which act as templates that can conform structurally and absorb the differential strain imposed by the more rigid Si and Si–Ge–Sn materials. The crystal structure, elemental distribution and morphological properties of the Si1−x−yGexSny/Ge1−xSnx heterostructures are characterized by high-resolution electron microscopy, including electron energy loss nanospectroscopy, x-ray diffraction (rocking curves) and atomic force microscopy. These techniques demonstrate growth of perfectly epitaxial, uniform and highly aligned layers with atomically smooth surfaces and monocrystalline structures that have lattice constants close to that of Ge. Rutherford backscattering ion channeling shows that the constituent elements occupy random substitutional sites in the same ave...

Scaling law for the compositional dependence of Raman frequencies in SnGe and GeSi alloys

The compositional dependence of the Ge–Ge Raman mode in SnGe alloys has been measured in samples grown on Si substrates using a chemical vapor deposition technique. The experimental result, Δω(s)=(−68±5)s (where s is the Sn concentration), is in very good agreement with a theoretical prediction from a simple model with parameters adjusted to the compositional dependence of Raman frequencies in GeSi alloys.

SnGe superstructure materials for Si-based infrared optoelectronics

We report growth of device-quality, single-crystal SnxGe1−x alloys (with x=0.02–0.2) directly on Si via chemical vapor deposition with deuterium-stabilized Sn hydrides. The high Sn-content materials are stabilized with ordered superstructures that gives rise to a layered structure adjacent to the Si substrate. Density functional theory simulations were used to elucidate the structural and bonding behavior of this material. Optical determinations show a Ge-like band structure that is substantially redshifted compared to that of elemental Ge. Thus, these systems are excellent candidates for a new generation of infrared devices, with the critical advantage that they can be grown directly on Si.

Redetermination of tetra-kis(trimethyl-stann-yl)germane.

Redetermination of the structure of the title compound, [Ge(SnMe3)4] or [GeSn4(CH3)12], previously refined from powder diffraction data only [Dinnebier, Bernatowicz, Helluy, Sebald, Wunschel, Fitch & van Smaalen et al. (2002 ▶). Acta Cryst. B58, 52–61], confirms that four bulky trimethylstannyl ligands surround the central Ge atom (site symmetry 1) in a tetrahedral coordination.

Optical Vibrational and Structural Properties of Ge1−xSn x alloys by UHV-CVD

Abstract : UHV-CVD growth based on a deuterium stabilized Sn hydride and digermane produces Ge-Sn alloys with tunable bandgaps. The Ge(1-x)Sn(x) (x=2-20 at.%) alloys are deposited on Si (100) and exhibit superior crystallinity and thermal stability compared with MBE grown films. Composition, crystal and electronic structure, and optical and vibrational properties are characterized by RBS, low energy SIMS, high resolution electron microscopy TEM, x-ray diffraction, as well as Raman and IR spectroscopies. TEM studies reveal epitaxial films with lattice constants between those of Ge and Sn. X-ray diffraction shows well-defined (004) peaks and rocking curves indicate a tightly aligned spread of the crystal mosaics. Resonance Raman indicate a E1 bandgap reduction relative to Ge, consistent with a decrease of the E2 critical point observed in spectroscopic ellipsometry. IR transmission spectra indicate an increase in absorption with increasing Sn content consistent with a decrease of the direct bandgap.