Room-temperature infrared sub-band gap photoresponse in silicon is of interest for telecommunications, imaging and solid-state energy conversion. Attempts to induce infrared response in silicon largely centred on combining the modification of its electronic structure via controlled defect formation (for example, vacancies and dislocations) with waveguide coupling, or integration with foreign materials. Impurity-mediated sub-band gap photoresponse in silicon is an alternative to these methods but it has only been studied at low temperature. Here we demonstrate impurity-mediated room-temperature sub-band gap photoresponse in single-crystal silicon-based planar photodiodes. A rapid and repeatable laser-based hyperdoping method incorporates supersaturated gold dopant concentrations on the order of 10 20 cm À 3 into a single-crystal surface layer B150 nm thin. We demonstrate room-temperature silicon spectral response extending to wavelengths as long as 2,200 nm, with response increasing monotonically with supersaturated gold dopant concentration. This hyperdoping approach offers a possible path to tunable, broadband infrared imaging using silicon at room temperature.

. 2004. Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon.

Silicon supersaturated with up to 0.6 at. % sulfur in solid solution was fabricated by ion implantation and pulsed-laser-melting-induced rapid solidification. The optical absorption coefficient over the range of 1200-2500 nm is uniformly high at ϳ2.5ϫ 10 4 / cm, which is at least an order of magnitude greater than the maximum value attributable to free carriers. High crystal quality was confirmed by transmission electron microscopy and ion channeling. The absorption coefficient decreases markedly with subsequent furnace annealing over the range of 200-600°C. We propose that the high absorptivity is due to a broad distribution of sulfur-related localized states within the band gap.

Emergence of very broad infrared absorption band by hyperdoping of silicon with chalcogens

Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein is reported a thin film of BaZrS3, a lead-free chalcogenide perovskite.Photoluminescence and X-ray diffraction measurements show that BaZrS3 is far more stable than methylammonium lead iodide (MAPbI3) in moist environments. Moisture-and lightinduced degradations in BaZrS3 and MAPbI3 are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS3 due to two factorsweak interaction with water, and very low rates of ion migration. BaZrS3 photo-detecting devices with photo-responsivity of ~46.5 mA W -1 are also reported. The devices retain ~60% of their initial photo-response after 4 weeks in ambient conditions. Similar MAPbI3 devices degrade rapidly and show ~95% decrease in photoresponsivity in just 4 days. The findings establish the superior stability of BaZrS3 and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.

Highly supersaturated solid solutions of selenium or sulfur in silicon were formed by ion implantation followed by nanosecond pulsed laser melting. n+p photodiodes fabricated from these materials exhibit gain (external quantum efficiency >3000%) at 12 V of reverse bias and substantial optoelectronic response to light of wavelengths as long as 1250 nm. The amount of gain and the strength of the extended response both decrease with decreasing magnitude of bias voltage, but >100% external quantum efficiency is observed even at 2 V of reverse bias. The behavior is inconsistent with our expectations for avalanche gain or photoconductive gain.

We report the near through mid-infrared (MIR) optical absorption spectra, over the range 0.05-1.3 eV, of monocrystalline silicon layers hyperdoped with chalcogen atoms synthesized by ion implantation followed by pulsed laser melting. A broad mid-infrared optical absorption band emerges, peaking near 0.5 eV for sulfur and selenium and 0.3 eV for tellurium hyperdoped samples. Its strength and width increase with impurity concentration. Its strength decreases markedly with subsequent thermal annealing. The emergence of a broad MIR absorption band is consistent with the formation of an impurity band from isolated deep donor levels as the concentration of chalcogen atoms in metastable local configurations increases. V C 2013 AIP Publishing LLC.

The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters where B is the kinetic rate constant for coalescence and f is the pulse frequency. Measurements of the percolation transition were consistent with this prediction. These findings indicate that the elementary processes included in the KMC simulation -substrate terrace diffusion, irreversible aggregation of hemispherical islands, and two-island coalescence, but neglecting the effects of Warrender & Aziz, Pg. 2 kinetic energy -are sufficient to explain the behavior observed when the pulse rate is varied at constant kinetic energy.