Material and optical characterizations have been conducted for epitaxially grown Ge1−xSnx thin films on Si with Sn composition up to 10%. A direct bandgap Ge0.9Sn0.1 alloy has been identified by temperature-dependent photoluminescence (PL) study based on the single peak spectrum and the narrow line-width. Room temperature PL emission as long as 2230 nm has also been observed from the same sample.

Germanium-tin alloys were grown directly on Si substrate at low temperatures using a coldwall ultra-high vacuum chemical-vapor-deposition system. Epitaxial growth was achieved by adopting commercial gas precursors of germane and stannic chloride without any carrier gases. The X-ray diffraction analysis showed the incorporation of Sn and that the Ge 1−x Sn x films are fully epitaxial and strain relaxed. Tin incorporation in the Ge matrix was found to vary from 1 to 7%. The scanning electron microscopy images and energy-dispersive X-ray spectra maps show uniform Sn incorporation and continuous film growth. Investigation of deposition parameters shows that at high flow rates of stannic chloride the films were etched due to the production of HCl. The photoluminescence study shows the reduction of band-gap from 0.8 to 0.55 eV as a result of Sn incorporation.

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The (Si)GeSn films have been grown with and without carrier gases on Si substrate using a cold-wall ultra-high vacuum chemical vapor deposition system. Material characterization of the films grown with Ar carrier gas using X-ray diffraction and transmission electron microscopy shows achievement of higher quality films. Optical characterization of the films with photoluminescence shows enhancement in material quality of the films at 350 and 400ºC growth temperatures. Increase in the pressure results in higher Sn incorporation and higher photoluminescence intensity. Spectroscopic ellipsometry data confirms the change in the GeSn bandgap towards lower energies.

Germanium films were deposited on silicon substrate by an ultra-high vacuum chemical vapor deposition system using GeH4 as Ge precursor and different carrier gases (Ar, N2 and H2). Silicon-germanium and SiGeSn films were deposited using optimized growth conditions of Ge growth. Silane and SnD4 were used as precursors for Si and Sn, respectively. A complete study of SiGe growth at chamber pressure from 0.1 to 1.0 torr and at temperatures from 350-450ºC for different SiH4 flow rate is performed. Silicon incorporation in Ge films varied from 1% to 17%. Tin incorporation of 2% was observed in the films with 17% Si incorporation. Investigation of film quality has been done using etch pit measurement, scanning electron microscopy and transmission electron microscopy. Threading dislocation density for Ge, SiGe and SiGeSn films were 1.7×107 cm-2, 2.3 ×107 cm-2 and 4.0 ×107 cm-2 , respectively.