Role of the Background Gas in the Morphology and Optical Properties of Laser-Microstructured Silicon

Sheehy, Michael; Winston, Luke; Carey, James E.; Friend, Cynthia M.; Mazur, Eric

doi:10.1021/cm049029i

Cited by 153 publications

(106 citation statements)

References 16 publications

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“…While the sub-band-gap absorption phenomenon is still not understood, dilute chalcogen atoms are known to form deep levels in the silicon band gap [18]. It has been proposed that, due to the high concentration of substitutional chalcogen incorporation, impurity bands within the Si forbidden gap may form and lead to the observed broad sub-band-gap absorption [8,19].…”

Section: Resultsmentioning

confidence: 99%

Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing

Tabbal

Kim²,

Woolf³

et al. 2009

Appl. Phys. A

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Selenium supersaturated silicon layers were fabricated by pulsed excimer laser induced liquid-phase mixing of thin Se films on Si(001) wafers. Sufficiently low Se coverage avoids destabilization of rapid epitaxial solidification, resulting in supersaturated solid solutions free of extended defects, as shown by transmission electron microscopy. The amount of retained Se depends on the original film thickness, the laser fluence, and the number of laser pulses irradiating the same spot on the surface. Using this method, Se has incorporated into the topmost 300 nm of the silicon with a concentration of 0.1 at.%. Channeling Rutherford backscattering spectrometry measurements show that the substitutional fraction can be as high as 75% of the total retained Se. These alloys exhibit strong sub-band-gap absorption with optical absorption coefficient ranging up to about 10 4 cm −1 , thus making them potential candidates for applications in Si-based optoelectronic devices. PACS 87.15. Nt · 78.66.Db · 79.20.Ds

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Section: Resultsmentioning

confidence: 99%

Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing

Tabbal

Kim²,

Woolf³

et al. 2009

Appl. Phys. A

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“…22 Second, carrier lifetimes, 23 carrier mobilities, 24 25 and absorption coefficients 26 1 in chalcogen-hyperdoped crystalline silicon have been measured and imply that the dopant concentration that maximizes carrier extraction from a hyperdoped silicon layer of a given optical thickness is around 0.03 atomic % (1.4×10 19 cm -3 ), 23 which is about two orders of magnitude greater than the equilibrium solubility limit for chalcogens in silicon of 0.0001 atomic % (5×10 16 cm -3 ). 27 Third, microstructural investigations of hyperdoped black silicon have shown that after fabrication with femtosecond laser irradiation, the light-trapping surface structures (typically cones that are 1-10 micrometers tall) are often polyphasic, containing amorphous and various pressure-induced crystalline silicon phases, and the dopants are incorporated within a thin layer on the surface which is typically 20-200 nm thick. 28 29 10 Fourth, thermal annealing increases the crystallinity of hyperdoped black silicon and can improve electrical rectification at the homojunction between the hyperdoped layer and the substrate, but thermal annealing also deactivates the sub-bandgap optical absorptance of the material in a manner consistent with the dopants diffusing to optically inactive sites in the silicon lattice (with diffusion lengths < 1 micrometer).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous high crystallinity and sub-bandgap optical absorptance in hyperdoped black silicon using nanosecond laser annealing

Franta

Pastor

Gandhi

et al. 2015

Journal of Applied Physics

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Hyperdoped black silicon fabricated with femtosecond laser irradiation has attracted interest for applications in infrared photodetectors and intermediate band photovoltaics due to its sub-bandgap optical absorptance and light-trapping surface. However, hyperdoped black silicon typically has an amorphous and polyphasic polycrystalline surface that can interfere with carrier transport, electrical rectification, and intermediate band formation. Past studies have used thermal annealing to obtain high crystallinity in hyperdoped black silicon, but thermal annealing causes a deactivation of the sub-bandgap optical absorptance. In this study, nanosecond laser annealing is used to obtain high crystallinity and remove pressure-induced phases in hyperdoped black silicon while maintaining high sub-bandgap optical absorptance and a light-trapping surface morphology. Furthermore, it is shown that nanosecond laser annealing reactivates the sub-bandgap optical absorptance of hyperdoped black silicon after deactivation by thermal annealing. Thermal annealing and nanosecond laser annealing can be combined in sequence to fabricate hyperdoped black silicon that simultaneously shows high crystallinity, high above-bandgap and sub-bandgap absorptance, and a rectifying electrical homojunction. Such nanosecond laser annealing could potentially be applied to non-equilibrium material systems beyond hyperdoped black silicon.

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“…12 The resulting material, socalled black silicon, presents strong optical absorption even at energies below the Si band gap. Near-unity absorptance has been found for photon energies down to approximately 0.5 eV.…”

Section: Introductionmentioning

confidence: 99%

Formation of a reliable intermediate band in Si heavily coimplanted with chalcogens (S, Se, Te) and group III elements (B, Al)

et al. 2010

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This first-principles study describes the properties of Si implanted with several chalcogen species (S, Se, Te) at doses considerably above the equilibrium solubility limit, especially when coimplanted with the group III atoms B and Al. The measurements of chalcogen-implanted Si show strong optical absorption in the infrared range. The calculations carried out show that substitution of Si by chalcogen atoms requires lower formation energy than the interstitial implantation. In the resulting electronic structure, at concentrations cióse to 0.5%, an impurity band determined by the properties of the chalcogens introduced is observed in the forbidden energy gap of Si. Although this band is a few tenths of an electrón volt wide, it remains energetically isolated from both the valence and the conduction bands. Appropriate coimplantation with group III elements allows control over the occupation of the intermedíate band while modifying its energies only slightly. A modérate energy gain (especially small for B) seems to be obtained when p-doping atoms occupy the sites next to those of the chalcogens. Therefore, the apparent electrostatic attraction between species that in isolation would act as acceptors and double donors is smaller than expected. The intermediate-band properties have been preserved for all of the coimplanted compounds analyzed here, regardless of the species involved or the distance between them, which constitutes an appreciable advantage for the design of new experimental materials. PACS number(s): 71.20. Be, 71.15.Mb, 71.28.+d

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Role of the Background Gas in the Morphology and Optical Properties of Laser-Microstructured Silicon

Cited by 153 publications

References 16 publications

Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing

Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing

Simultaneous high crystallinity and sub-bandgap optical absorptance in hyperdoped black silicon using nanosecond laser annealing

Formation of a reliable intermediate band in Si heavily coimplanted with chalcogens (S, Se, Te) and group III elements (B, Al)

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