Electronic and Vibrational Properties of GeSn and SiGeSn Alloys

GeSn and SiGeSn alloys posses an intriguing §potential for IR optoelectronics and photovoltaic §applications. This book reports a detailed §compositional study of the electronic and §vibrational properties of GeSn and SiGeSn alloys. §The various optical transition energies in the §electronic band structure of the alloys are obtained §by spectroscopic ellipsometry and photoreflectance. §From the analysis, GeSn alloys are predicted to be a §direct gap material for Sn concentration as low as 6-§11 %. The bowing of optical transitions in GeSn and §SiGeSn alloys is found to scale with the atomic size §mismatch and electronegativity difference between §Si, Ge and -Sn. The Raman spectra of GeSn alloys §show two optical modes and two disorder-activated §modes. The Raman spectra of SiGeSn alloys are SiGe §like and the compositional dependence of vibrations §can be expressed in terms of the corresponding §vibrations in the binaries constituting the ternary §alloys. This experimental work should be useful to §scientists and engineers in the semiconductor field §and to anyone who is interested in learning the §basic optical properties of these novel materials. GeSn and SiGeSn alloys posses an intriguing §potential for IR optoelectronics and photovoltaic §applications. This book reports a detailed §compositional study of the electronic and §vibrational properties of GeSn and SiGeSn alloys. §The various optical transition energies in the §electronic band structure of the alloys are obtained §by spectroscopic ellipsometry and photoreflectance. §From the analysis, GeSn alloys are predicted to be a §direct gap material for Sn concentration as low as 6-§11 %. The bowing of optical transitions in GeSn and §SiGeSn alloys is found to scale with the atomic size §mismatch and electronegativity difference between §Si, Ge and -Sn. The Raman spectra of GeSn alloys §show two optical modes and two disorder-activated §modes. The Raman spectra of SiGeSn alloys are SiGe §like and the compositional dependence of vibrations §can be expressed in terms of the corresponding §vibrations in the binaries constituting the ternary §alloys. This experimental work should be useful to §scientists and engineers in the semiconductor field §and to anyone who is interested in learning the §basic optical properties of these novel materials.