Photocarrier lifetime and transport in silicon supersaturated with sulfur

Persans, P. D.; Berry, Nathaniel E.; Recht, Daniel; Hutchinson, David; Peterson, Hannah; Clark, Jessica; Charnvanichborikarn, Supakit; Williams, James S.; DiFranzo, Anthony; Aziz, Michael J.; Warrender, Jeffrey M.

doi:10.1063/1.4746752

Cited by 29 publications

(28 citation statements)

References 18 publications

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“…Charge carriers in hyperdoped silicon have short carrier lifetimes on the order of picoseconds 23 , so the hyperdoped layer must be thin enough to allow carriers to be transported out of the layer before recombination occurs. The transport length for holes in sulfur-hyperdoped silicon was estimated in one study to be around 100 nm, 25 but in general the transport length can be expected to depend on a number of factors, including the dopant concentration, the material microstructure, and electrostatic fields set up by the dopant concentration gradient. If the electrostatic fields set up by the dopant concentration gradient prove to be a limiting factor in carrier transport, then it might necessary to control the dopant concentration gradient 58 59 (e.g., producing a monotonic dopant concentration profile with depth) in order to fabricate efficient hyperdoped intermediate band photovoltaics or subbandgap photodetectors.…”

Section: Discussionmentioning

confidence: 99%

“…Second, the thickness of the hyperdoped layer should be less than the carrier transport lengths. (The transport length for holes in sulfur-hyperdoped silicon, for example, was estimated in one study to be at least 100 nm under an internal field produced by the dopant concentration gradient 25 ). Because the transport length is generally less than the optical absorption depth, light trapping strategies, such as geometric light trapping from surface structures or plasmonic light trapping from metal nanoparticles, should be used to increase absorption within the hyperdoped layer.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

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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“…13 Microwave photoconductivity decay and low-temperature photoconductivity measurements on carrier dynamics in this material lack the time-resolution required to measure the lifetime directly. [14][15][16] Similar to microwaves, THz radiation is long-wavelength electromagnetic radiation and is sensitive to free charge carriers. Moreover, subpicosecond-duration THz pulses can be straightforwardly generated, enabling direct mapping of the carrier recombination dynamics on picosecond time scales.…”

Section: à3mentioning

confidence: 99%

Picosecond carrier recombination dynamics in chalcogen-hyperdoped silicon

Sher

Simmons

Krich

et al. 2014

Applied Physics Letters

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Intermediate-band materials have the potential to be highly efficient solar cells and can be fabricated by incorporating ultrahigh concentrations of deep-level dopants. Direct measurements of the ultrafast carrier recombination processes under supersaturated dopant concentrations have not been previously conducted. Here, we use optical-pump/terahertz-probe measurements to study carrier recombination dynamics of chalcogen-hyperdoped silicon with sub-picosecond resolution. The recombination dynamics is described by two exponential decay time scales: a fast decay time scale ranges between 1 and 200 ps followed by a slow decay on the order of 1 ns. In contrast to the prior theoretical predictions, we find that the carrier lifetime decreases with increasing dopant concentration up to and above the insulator-to-metal transition. Evaluating the material's figure of merit reveals an optimum doping concentration for maximizing performance.

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“…3,4,18 In this article, we will focus on the latter concept, which has been studied extensively from a materials standpoint in two primary material systems: silicon hyperdoped with Ti (Si:Ti) [19][20][21][22][23][24][25][26] and silicon hyperdoped with sulfur (Si:S). [27][28][29][30][31][32][33][34][35] Despite significant efforts on these impurity-band materials, no high-efficiency devices have been demonstrated. We present an experimental framework that predicts whether a candidate impurity-band material system will actually enhance the efficiency of a photovoltaic (PV) device.…”

Section: Introductionmentioning

confidence: 99%

Methodology for vetting heavily doped semiconductors for intermediate band photovoltaics: A case study in sulfur-hyperdoped silicon

Sullivan

Simmons

Krich

et al. 2013

Journal of Applied Physics

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We present a methodology for estimating the efficiency potential for candidate impurity-band photovoltaic materials from empirical measurements. This methodology employs both Fourier transform infrared spectroscopy and low-temperature photoconductivity to calculate a "performance figure of merit" and to determine both the position and bandwidth of the impurity band. We evaluate a candidate impurity-band material, silicon hyperdoped with sulfur; we find that the figure of merit is more than one order of magnitude too low for photovoltaic devices that exceed the thermodynamic efficiency limit for single band gap materials. V C 2013 AIP Publishing LLC. [http://dx

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Photocarrier lifetime and transport in silicon supersaturated with sulfur

Cited by 29 publications

References 18 publications

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

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

Picosecond carrier recombination dynamics in chalcogen-hyperdoped silicon

Methodology for vetting heavily doped semiconductors for intermediate band photovoltaics: A case study in sulfur-hyperdoped silicon

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