Liquid phase diffusion growth of SiGe single crystals under magnetic fields

The manuscript presents the results of a combined experimental and modeling study on the Liquid Phase Diffusion (LPD) growth of single crystal SixGe1-x on Germanium with and with the application of magnetic fields. Although the LPD process is mainly diffusion driven through out the growth period, strong natural thermosolutal convection occurs in the first five hours of growth, and the growth interface is concave to the melt. Applied rotating and static magnetic fields were considered to examine the growth and silicon dissolution processes in the LPD system. Results show that the application of a combined applied magnetic is beneficial

Optical properties of SiGe single crystals grown by liquid phase diffusion

In this article, we present measurements for the pseudo-optical functions of germanium-rich SixGe1-x (0.000<x<0.100) single-crystals(grown by Liquid Phase Diffusion; LPD) using spectroscopic ellipsometry and photo reflectance techniques in the energy range of 1.72–3.20 eV. The E1 interband transition energies are obtained from numerically differentiated optical spectra for various crystal compositions. It was shown that the values of E1 interband transition energy determined by both the ellipsometric and photo reflectance measurements for germanium-rich SixGe1-x single-crystals are in agreement with those of bulk SiGe crystals reported in the literature[21–24].The interband transition energies are found to be in the range of 2.100 and 2.215 eV for the composition values of 0.000<x0.100. The surface morphology of the crystals assayed via atomic force microscopy shows fibrous surfaces with the average grain size of 250 nm. The measured root-mean-square (rms) roughness and maximum height are in the range of 3.78–5.40 and 32.42–67.84 nm, respectively, with increasing germanium composition

Mathematical modeling of the dissolution process of silicon into germanium melt

Numerical simulations were carried out to study the thermosolutal and flow structures observed in the dissolution experiments of silicon into a germanium melt. The dissolution experiments utilized a material configuration similar to that used in the Liquid Phase Diffusion (LPD) and Melt-Replenishment Czochralski (Cz) crystal growth systems. In the present model, the computational domain was assumed axisymmetric. Governing equations of the liquid phase (Si-Ge mixture), namely the equations of conservation of mass, momentum balance, energy balance, and solute (species) transport balance were solved using the Stabilized Finite Element Methods (ST-GLS for fluid flow, SUPG for heat and solute transport). Measured concentration profiles and dissolution height from the samples processed with and without the application of magnetic field show that the amount of silicon transported into the melt is slightly higher in the samples processed under magnetic field, and there is a difference in dissolution interface shape indicating a change in the flow structure during the dissolution process. The present mathematical model predicts this difference in the flow structure. In the absence of magnetic field, a flat stable interface is observed. In the presence of an applied field, however, the dissolution interface remains flat in the center but curves back into the source material near the edge of the wall. This indicates a far higher dissolution rate at the edge of the silicon source.We gratefully acknowledge the financial support provided by the Canadian Space Agency (CSA), Canada Research Chairs (CRC) Program, and the Natural Sciences and Engineering Research Council (NSERC) of Canada.Publisher's Versio

Growth of bulk SiGe single crystals by liquid phase diffusion method: experimental and computational aspects

SiGe is an emerging semiconductor material with many promising applications in high-speed micro electronics and thermo-photovoltaics. In light of significant differences in physical properties of constituent elements, it is still a challenge to grow bulk SiGe single crystals with uniform composition and low defect density. Thus, it is essential to scrutinize the solidification behaviour of SiGe system. Hence, this book presents a combined experimental and modelling study for the growth of SiGe single crystals by a new solution growth process called Liquid Phase Diffusion (LPD). Following a brief introduction of the subject, the crystal structure, phase diagram, growth techniques used for producing SiGe single crystals and their place in the overall scheme of SiGe alloy systems are presented. The development of a macroscopic mixture model is presented to model the LPD growth system. The LPD growth system is examined using two- and three-dimensional transient simulations. The design, construction, and testing of the LPD growth system are presented along with the experimental results and characterization of grown crystals

Modeling of combined natural/thermocapillary convection flows in germanium melt at high temperatures

A mathematical model for the description of combined natural/ thermocapillary convection melt flows in cylindrical (3D) geometry is developed. It is utilized to model germanium melt convective flows in an isothermal experimental crucible setup. This experimental setup is devised exclusively to study the dissolution phenomenon of silicon into germanium melt. In this system, the germanium melt is subjected to higher temperatures. Using a simplified axisymmetric (2D) model, numerical simulations are carried out to examine the combined natural/thermocapillary flows developing in the germanium melt. Pure thermocapillary and pure natural convective flows are also studied numerically.Publisher's Versio

Optical properties of Si x Ge 1Àx single crystals grown by liquid phase diffusion

a b s t r a c t In this article, we present measurements for the pseudo-optical functions of germanium-rich Si x Ge 1Àx (0.000rxr0.100) single-crystals (grown by Liquid Phase Diffusion; LPD) using spectroscopic ellipsometry and photoreflectance techniques in the energy range of 1.72-3.20 eV. The E 1 interband transition energies are obtained from numerically differentiated optical spectra for various crystal compositions. It was shown that the values of E 1 interband transition energy determined by both the ellipsometric and photoreflectance measurements for germanium-rich Si x Ge 1Àx single-crystals are in agreement with those of bulk SiGe crystals reported in the literatur