(a) Schematic illustration of deformation of Ge and Si crystals before and after cooling from a high-temperature to a low-temperature , (b) calculated results of strain as a function of in a -thick (001) Ge layer on a -thick (001) Si substrate for several different starting temperatures for cooling and (c) calculated result of strain in the Ge at RT (300 K) as a function of .
Calculated results of C–HH and C–LH direct band-gap energies of biaxially strained (001) Ge as a function of the in-plane strain.
(a) Typical XRD curves from the -thick Ge layer on Si (sample F: solid line) and bulk Ge (dashed line) and (b) in-plane strain by XRD as a function of starting temperature for cooling. The solid line shows the theoretical one.
Typical PR spectra from samples E and F, which have the Ge layer with 0.20% tensile strain (bottom). Solid lines show the experimental spectra and dashed lines show the fitting results. The arrows show the C–LH and C–HH band-gap energies determined by the fitting of the spectra. Spectrum from the bulk Ge (middle) and theoretical relationship between the band-gap energies and the strain (top) are also shown.
(a) Typical responsivity spectrum obtained for a Ge pin photodiode on a -Si wafer and (b) absorption coefficient of Ge layer on Si calculated using Eq. (8b). In (b), absorption coefficient for bulk Ge after Ref. 36 is also shown.
Comparisons of absorption coefficient between experiment and theory for (a) bulk Ge and for (b) Ge layer on Si.
Calculated responsivity spectra of photodiodes having -thick Ge layer with the tensile strain of 0–0.6%.
Summary of grown samples.
Fitting results of PR spectra.
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