Absorptance of chalcogen-hyperdoped silicon. Data for a control sample (Si:N2) and the silicon substrate (c-Si) are also plotted for comparison. Data from 0.09 to 0.62 eV was collected using an FTIR spectrometer and data from 0.5 to 1.5 eV was collected using a UV-VIS-NIR spectrophotometer. The mismatch between the data from two instruments at 0.5 eV is about 3%.
Scanning electron micrographs of fs-laser hyperdoped silicon. The images are taken at a 45° angle to the surface. Si:S-1, Si:Se, Si:Te, and Si:N2 are irradiated with the same fs-laser parameter: 4 kJ/m2, 80 pulses. Si:S-2 is irradiated with 8 kJ/m2, 50 pulses. After annealing, we examined all samples under SEM and observed no change in surface morphology in any of the samples.
(a) Illustration of light propagation though micrometer-scale structures with spacing w and height h, as well as the corresponding reflectance and transmittance as a function of photon energy (proportional to inverse wavelength). Three wavelength ranges represent different light and matter interactions: optically smooth (left), graded density (middle), and multiple reflections (right). The representative wavelengths are shown for the incoming light (gray); for each wavelength, three arrows indicate incoming, reflected, and transmitted light. (b) Reflectance and transmittance spectra of Si:Se (brown) and Si:Te (green) between 0.09 and 0.2 eV. The vertical dashed lines at 0.11 eV (11.3 μm) and 0.16 eV (7.6 μm) correspond to transition wavelengths at 2.5h and 2w, respectively.
Mid-infrared absorptance of Si:S-2, Si:Se, and Si:Te before (black) and after annealing at 730 K (blue) and 990 K (red). Except for the gray line, all Si:S-2 data are taken after a 5% HF etch for 1 min and the surface oxide absorption band from 0.13 to 0.15 eV is removed. Labels correspond to absorption features phonon vibrations and other contaminants: hydroxide (OH; centered at 0.42 eV), 44 hydrocarbon (CH; three peaks near 0.36 eV), 44 silicon phonons (below 0.13 eV and between 0.16–0.18 eV), 45 and CO2 molecules in the spectrometer (0.29 eV). 46 The curves are fits of the free carrier absorption model in Eq. (2) :
Average surface feature spacing w and height h.
Hall-effect and resistivity measurements of Se- and Te-hyperdoped Si after annealing.
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