Low temperature growth of high crystallinity GeSn on amorphous layers for advanced optoelectronics

High crystallinity GeSn substitutional alloy thin films with up to 8.7 at.% Sn are directly grown on amorphous SiO2 layers at low crystallization temperatures of 370~470 °C for potential applications in 3D electronic-photonic integration on Si as well as inexpensive virtual substrates for tandem solar cells. The optimal Ge0.913Sn0.087 thin film demonstrates a strong (111) texture and an average gain size of 10 μm, and its grain boundaries are mostly twin and low-angle boundaries with low densities of defect recombination centers. The 8.7 at.% Sn incorporated substitutionally into the Ge lattice far exceeds the ~1 at.% equilibrium solubility limit. Correspondingly, the direct band gap is significantly red-shifted from 0.8 eV for pure Ge to ~0.5 eV for crystalline Ge0.913Sn0.087, right at the verge of the indirect-to-direct gap transition that occurs at 8-10 at.% Sn alloying. Optoelectronic properties are greatly enhanced due to this transition.

[1]  M. Lipson,et al.  CMOS-compatible athermal silicon microring resonators. , 2009, Optics express.

[2]  Effect of grain alignment on lateral carrier transport in aligned-crystalline silicon films on polycrystalline substrates , 2007 .

[3]  H. Atwater,et al.  Selective solid phase crystallization for control of grain size and location in Ge thin films on silicon dioxide , 1996 .

[4]  Jurgen Michel,et al.  High performance, waveguide integrated Ge photodetectors. , 2007, Optics express.

[5]  B. Jalali,et al.  Multilayer 3-D photonics in silicon. , 2007 .

[6]  Richard A. Soref,et al.  Direct-gap Ge/GeSn/Si and GeSn/Ge/Si heterostructures , 1993 .

[7]  James S. Harris,et al.  Increased photoluminescence of strain-reduced, high-Sn composition Ge1−xSnx alloys grown by molecular beam epitaxy , 2011 .

[8]  Randolph Kirchain,et al.  A roadmap for nanophotonics , 2007 .

[9]  Richard A. Soref,et al.  Advances in SiGeSn technology , 2007 .

[10]  Gerald Siefer,et al.  Current-matched triple-junction solar cell reaching 41.1% conversion efficiency under concentrated sunlight , 2009 .

[11]  J. Tolle,et al.  Direct gap electroluminescence from Si/Ge1−ySny p-i-n heterostructure diodes , 2011 .

[12]  Jurgen Michel,et al.  Direct-gap optical gain of Ge on Si at room temperature. , 2009, Optics letters.

[13]  M. Miyao,et al.  Ge-enhanced MILC velocity in a-Ge/a-Si/SiO2 layered structure , 2005 .

[14]  A. G. Rodríguez,et al.  Ge1-xSnx alloys pseudomorphically grown on Ge(001) , 2003 .

[15]  J. Michel,et al.  Ge-on-Si laser operating at room temperature. , 2010, Optics letters.

[16]  R. Soref,et al.  The Past, Present, and Future of Silicon Photonics , 2006, IEEE Journal of Selected Topics in Quantum Electronics.

[17]  A. Chizmeshya,et al.  Thermal expansivity of Ge1-y sny alloys , 2010 .

[18]  Paul Handler,et al.  Franz-Keldysh Effect in the Space-Charge Region of a Germanium p − n Junction , 1965 .

[19]  Stefan Zollner,et al.  Optical critical points of thin-film Ge 1-y Sn y alloys: A comparative Ge 1-y Sn y /Ge 1-x Si x study , 2006 .

[20]  Jörg Schulze,et al.  Germanium-tin p-i-n photodetectors integrated on silicon grown by molecular beam epitaxy , 2011 .

[21]  Harry A. Atwater,et al.  INTERBAND TRANSITIONS IN SNXGE1-X ALLOYS , 1997 .

[22]  R. J. Jaccodine,et al.  Surface Energy of Germanium and Silicon , 1963 .

[23]  Mark Beals,et al.  Process flow innovations for photonic device integration in CMOS , 2008, SPIE OPTO.

[24]  John Tolle,et al.  Raman scattering in Ge1−ySny alloys , 2007 .

[25]  Jurgen Michel,et al.  Waveguide-integrated, ultralow-energy GeSi electro-absorption modulators , 2008 .

[26]  P. Yeh,et al.  Metal-induced crystallization of amorphous Si1−xGex by rapid thermal annealing , 2004 .

[27]  Van de Walle Cg Band lineups and deformation potentials in the model-solid theory. , 1989 .

[28]  Sarah R. Kurtz,et al.  High-Efficiency Multijunction Solar Cells , 2007 .