Temperature varying photoconductivity of GeSn alloys grown by chemical vapor deposition with Sn concentrations from 4% to 11%

Abstract

Pseudomorphic GeSn layers with Sn atomic percentages between 4.5% and 11.3% were grown by chemical vapor deposition using digermane and SnCl4 precursors on Ge virtual substrates grown on Si. The layers were characterized by x-ray diffraction rocking curves and reciprocal space maps. Photoconductive devices were fabricated, and the dark current was found to increase with Sn concentration. The responsivity of the photoconductors was measured at a wavelength of 1.55 μm using calibrated laser illumination at room temperature and a maximum value of 2.7 mA/W was measured for a 4.5% Sn device. Moreover, the responsivity for higher Sn concentration was found to increase with decreasing temperature. Spectral photoconductivity was measured using Fourier transform infrared spectroscopy. The photoconductive absorption edge continually increased in wavelength with increasing tin percentage, out to approximately 2.4 μm for an 11.3% Sn device. The direct band gap was extracted using Tauc plots and was fit to a bandgap model accounting for layer strain and Sn concentration. This direct bandgap was attributed to absorption from the heavy-hole band to the conduction band. Higher energy absorption was also observed, which was thought to be likely from absorption in the light-hole band. The band gaps for these alloys were plotted as a function of temperature. These experiments show the promise of GeSn alloys for CMOS compatible short wave infrared detectors.

Stereochemistry of Simple Molecules inside Nanotubes and Fullerenes: Unusual Behavior of Usual Systems

“…The experimental barrier of rotation about the Ge-Ge bond in digermane corresponds to 1.2 kcal/mol [157]. On the other hand, this compound is widely used in epitaxial technology for the creation of mono-or polycrystalline thin films on the surfaces of silicon [158][159][160][161], tin [162], and germanium [163,164], with remarkable semiconducting properties. In this connection, endohedral nanocomplexes containing Ge 2 H 6 are interesting as an important component in this process.…”

Progress on Germanium–Tin Nanoscale Alloys

“…Naturally, this can be predicted as the lower energies are expected due to the reducing energy of the Γ-valley. Due to the presence of band mixing, Ge 1– x Sn x alloys also have a broad spectral response, across all telecommunications bands. ,, A strong spectral response has been observed for Ge 1– x Sn x thin films (0.045 < x < 0.052) compared to pure Ge thin films or, indeed, for samples with x > 0.052 which showed similar magnitudes at 1550 nm . This consistency of responsivity of Ge 1– x Sn x devices with increasing x indicates that a photodetector comprised of Ge 1– x Sn x will be of equal, or greater, quality than a Ge photodetector.…”

“…57,168,169 A strong spectral response has been observed for Ge 1−x Sn x thin films (0.045 < x < 0.052) compared to pure Ge thin films or, indeed, for samples with x > 0.052 which showed similar magnitudes at 1550 nm. 170 This consistency of responsivity of Ge 1−x Sn x devices with increasing x indicates that a photodetector comprised of Ge 1−x Sn x will be of equal, or greater, quality than a Ge photodetector. Hart et al 170 dark conductivity three times higher than that of their Ge reference.…”

“…170 This consistency of responsivity of Ge 1−x Sn x devices with increasing x indicates that a photodetector comprised of Ge 1−x Sn x will be of equal, or greater, quality than a Ge photodetector. Hart et al 170 dark conductivity three times higher than that of their Ge reference. In fact, it was noted that, at room temperature, the dark conductance increased with increasing Sn content.…”

Studies on plasma assisted molecular beam epitaxial growth of GaN-based multilayer heterostructures on Si for photodetector application

“…This approach is limited by interconnect size and losses, which affects performance, restricts the minimum pixel and chip sizes and augments the cost and complexity [279][280][281][282]. Another method is GeSn photodetectors grown on silicon, which have been reported to extend the detection wavelength up to 2.4 μm [283], yet further extension of the operating wavelength is challenging [284].…”