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(a) RBS spectra of a 1 μm-thick Ge0.886Si0.094Sn0.02 film showing a high degree of crystallographic alignment with the Ge substrate; (b) XRD 2θ/ω plot and 224 reciprocal space map (inset) indicating very close lattice-matching between the film and the substrate.
XTEM data for a 700-nm-thick Ge0.92Si0.065Sn0.015/Ge(100) pin device as-grown at 300 °C. (a) Image of the sloped heterojunction marked by arrows indicating conformal and fully commensurate film growth on the offcut Ge wafer; (b) micrograph of the entire film showing a defect-free microstructure (arrow denotes the surface of the film); (c) image of the surface edge showing nanometer-scale steps essentially replicating the interface profile.
(a) I-V curves of Ge1−x−y Si x Sn y (y = 0.01–0.05) devices measured from their respective 300 μm mesas. The inset is a schematic of the device; (b) EQE for a heterostructure diode with composition Ge0.91Si0.07Sn0.020 measured at zero bias. The data show the absorption edges for the Ge substrate near 1600 nm and the epilayer at 1360 nm.
(a) Normalized EQE plots of diodes with 1%–4% Sn content. The inset shows the numerical derivative of EQE for one of the diodes. The solid black line is a Gaussian fit from which the E 0 gap is determined. (b) The solid spheres show the measured E 0 gap energies as a function of the Si- and Sn-concentrations. The colored plane is a bilinear fit of these energies, whose linear coefficients are given in Eq. (1). The solid line in the concentration plane indicates the Si/Sn concentrations that give a perfect lattice match between Ge1− x − y Si x Sn y and the Ge substrate.
Temperature dependence of the dark current at −0.5 V bias for selected Ge1− x − y Si x Sn y /Ge diodes. The lines represent Arrhenius fits from which the activation energy Ea is obtained. The inset shows the dark current ideality factor m.
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