Bridgman and Czochralski growth of GeSi alloy crystals

Abstract

Ge, -,Six crystals were grown with the Bridgman and the Czochralski method over a wide concentration range. With the Bridgman process single crystals up to 40 at.% Si were possible. The reasons for polycrystalline growth were the permanent contact of the interface with the crucible wall in combination with curvature towards the crystal and inclusions of high Si concentration. Analysis of striations in Czochralski grown material showed that in this process the crystal does not continuously grow in one direction but consists of piece-wise grown crystals in which the composition permanently changes. According to that fact the main reason for polycrystalline growth in the Czochralski process is common due to lattice mismatch between the seed and equilibrium concentration transients in the crystal corresponding to the microscopic growth rates.Sowohl mit dem Bridgman-als auch mit dem Czochralski-Verfahren wurden Gel _,Si,-Kristalle uber einen weiten Konzentrationsbereich hergestellt. Mit dem Bridgman-Verfahren gelang auf der Ge-Seite die Herstellung von einkristallinem Material rnit einem Si-Gehalt von 40 at.%. Als Grunde fur polykristallines Wachstum wurden einerseits der standige Kontakt der Phasengrenze rnit der Tiegelwand in Verbindung mit einer zum Kristall konkav gekrummten Phasengrenze, andererseits der Einschlulj von Bereichen rnit stark erhohter Si-Konzentration ermittelt. Anhand der Analyse von Wachstumsstreifen in Czochralski-Kristallen wurde festgestellt, d a 8 bei diesem Verfahren der Kristall nicht monoton in eine Richtung, sondern bei periodischem Anwachsen und Abschmelzen rnit kurzzeitig variierender Zusammensetzung wlchst. Als Hauptgrund fur polykristallines Wachstum wird eine damit zusammenhangende starke Gitterparameterschwankung vermutet.

Bulk growth of silicon-germanium solid solutions

“…The results derived from the FZ solidification experiments support the findings of diffusion controlled segregation profiles during directional solidification [38][39][40]. In spite of the rather slow processing speed, it seems that the mixing of the melt is not complete.…”

“…In CZ-growth, solidified crystals do not have any contact to the container and the unavoidable cracking during the cooling phase does not pose any difficulty. This makes quartz the material of choice for Si-Ge CZ growthl Also for zone melting/leveling [9,25] of all Si-Ge compositions or Bridgman growth of Ge-rich material [38,40], the use of quartz boats and ampoules, respectively, is reported. By using extremely slow cooling rates, cracking of containers or ingots could be mostly avoided -however, a reaction between crystal and ampoule was still detected and identified as a source for polycrystalline growth.…”

Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles

“…Furthermore, we noticed apparent striations in the germanium concentration for Si 0.95 Ge 0.05 samples, with a periodicity around 15 μm. Such fluctuations are common in the growth of SiGe from both Czochralski and Bridgman processes (31)(32)(33). Generally these striations show a 10-to 15-μm periodicity independent of growth conditions, and commonly attributed to fluctuations in growth velocity associated with time-dependent temperature fluctuations at the interface that can be due to convection or fluctuations in solid-phase conductivity (31-33).…”

Evolution of the growth interface in liquid phase diffusion growth of bulk SiGe single crystals

“…Therefore, the availability of high quality and relatively defect free and compositionally uniform Si x Ge 1-x substrates is desirable, and will allow the deposition of thicker lattice matched alloys with high compositions. In order to achieve high quality Si x Ge 1-x crystals with different germanium contents, a variety of melt crystal growth techniques, such as Czochralski (Cz) [20][21][22][23], floating zone (FZ) [24], Bridgman [25,26], multi component [9], and liquid encapsulated zone melting [27], have been utilized. It is however difficult to grow single crystals by Cz [20,21], Bridgman [25,26] or FZ [24].…”