Codoping as a measure against donor deactivation in Si:<i>Ab initio</i>calculations

Mueller, D. Christoph; Fichtner, W.

doi:10.1103/physrevb.73.035210

Cited by 6 publications

(4 citation statements)

References 27 publications

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“…74 A possible solution is co-doping with an electrically not active impurity that has a stronger binding with the vacancy than the dopant atom. Ab initio calculations show that co-doping with Ge or C is not effective due to their weak binding with the vacancy 75 as is also apparent from Table III. The calculations also suggest that Mg might be a suitable co-dopant in n-type Si to reduce the vacancy concentration as it shows a strong binding energy with the vacancy and at the same time when complexes are formed has a tendency to act as a donor.…”

Section: Impact Of the Fermi Level On [V/ G0] Cr I Tmentioning

confidence: 86%

Silicon Single Crystal Growth from a Melt: On the Impact of Dopants on thev/GCriterion

Vanhellemont

Kamiyama

Sueoka

2013

ECS J. Solid State Sci. Technol.

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The so called v/G criterion defines a critical value 0 crit of the ratio of the pulling rate v over the thermal gradient G at the melt-solid/interface. For a ratio larger than this critical value, the crystal is vacancy-rich while for values below the critical value, the crystal is self-interstitial-rich. When the ratio is equal to the critical value, the crystal would be defect free or made of so called "perfect silicon". The basic analytical expression for the critical ratio is analyzed and it is shown that thermal stress at the melt-solid interface and doping have an important effect on the 0 crit value. Furthermore, DFT calculations suggest that near the melt-solid interface the formation energy of the intrinsic point defects is lower than in the bulk of the crystal. This would lead to thermal equilibrium concentrations of vacancies and self-interstitials at the free surface and most probably also at the melt-solid interface that are considerably different from those in the bulk. It is illustrated how the v/G criterion can be further refined by taking into account these effects.The so called "Voronkov criterion" which allows predicting if a Si single crystal pulled from a melt will be vacancy-or self-interstitialrich, is the basis for defect-free Si crystal and wafer production. In its most simple form it is written as the critical ratio 0 crit of the pulling speed v over the thermal gradient G0 at the melt-solid interface 1-3with C eq and D the intrinsic point defect thermal equilibrium concentration and diffusivity, respectively, both at the melt temperature T m . E f is the intrinsic point defect formation energy and C the actual concentration of the intrinsic point defects at the melt-solid interface. The criterion was later further generalized by including also the possible effect of vacancy and self-interstitial drift which was shown however to be of minor importance. 3 An important question is which values one should use for the thermodynamic parameters of the intrinsic point defects in Eq. 1 as a very wide range of values have been reported in literature. The values for the self-diffusion coefficient D S D Si have however converged during the last years and in the temperature range between 855 and 1388 • C, D S D Si (in cm 2 s −1 ) is accurately described by 4with f I and f V the diffusion-correlation factors for self-interstitials and vacancies, respectively. Also the uncertainty on the transport capacity C eq D of the vacancy and the self-interstitial has decreased significantly. Assuming f I = 0.73, Bracht et al. 5,6 obtained (in cm −1 s −1 ) C eq V D V = 6.2C Si exp − 4.33 eV k B T [3] C eq I D I = 43C Si exp − 4.56 eV k B T . For the diffusivity of the vacancy Watkins recently proposed best estimates (in cm 2 s −1 ) for the double positively charged vacancy V 2+ and for the uncharged vacancy V 0 diffusivities, given by 7 D V 2+ = 6.5 × 10 −5 exp − 0.32 eV k B T [4] D V 0 = 0.0012 exp − 0.45 eV k B T . * Electrochemical Society Active Member. z E-mail: jan.vanhellemont@ugent.be Combining Eqs. 3 an...

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Section: Impact Of the Fermi Level On [V/ G0] Cr I Tmentioning

confidence: 86%

Silicon Single Crystal Growth from a Melt: On the Impact of Dopants on thev/GCriterion

Vanhellemont

Kamiyama

Sueoka

2013

ECS J. Solid State Sci. Technol.

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“…Transistors beyond the 14 nm node will require electrically active dopant concentrations in excess of ∼10 21 cm –3 to maintain performance, far beyond what is currently possible using traditional doping techniques such as ion implantation . The use of two-dimensional doping methods has been suggested as a means to achieve higher active dopant concentrations in a range of materials for ultrashallow junctions, − avoiding the formation of deactivating dopant pairs in adjacent crystallographic planes. In particular, monolayer doping of Si has been used to produce high n -type sheet densities in silicon 2DEGs, reaching active carrier densities of (2–3) × 10 14 cm –2 for both Sb and P dopants. , Recently, it has been demonstrated that an optimized double-dosing recipe yields a maximum active carrier density of n s = (3.6 ± 0.1) × 10 14 cm –2 (∼0.5 ML) in a single Si:P δ-layer without the formation of deactivating dopant precipitates .…”

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confidence: 99%

The Impact of Dopant Segregation on the Maximum Carrier Density in Si:P Multilayers

2015

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Abrupt dopant profiles and low resistivity are highly sought after qualities in the silicon microelectronics industry and, more recently, in the development of an all epitaxial Si:P based quantum computer. If we increase the active carrier density in silicon to the point where the material becomes superconducting, while maintaining a low thermal budget, it will be possible to fabricate nanoscale superconducting devices using the highly successful technique of depassivation lithography. In this work, we investigate the dopant profile and activation in multiple high density Si:P δ-layers fabricated by stacking individual layers with intervening silicon growth. We determine that dopant activation is ultimately limited by the formation of P-P dimers due to the segregation of dopants between multilayers. By increasing the encapsulation thickness between subsequent layers, thereby minimizing the formation of these deactivating defects, we are able to achieve an active carrier density of ns = 4.5 ×10(14) cm(-2) for a triple layer. The results of electrical characterization are combined with those of secondary ion mass spectroscopy to construct a model that accurately describes the impact of P segregation on the final active carrier density in Si:P multilayers. Our model predicts that a 3D active carrier density of 8.5 × 10(20) cm(-3) (1.7 atom %) can be achieved.

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“…Ab initio calculations reveal that formation of C-As complex has a deactivating effect because the C-As complex is electrically inactive and neutral at high Fermi level. 21 Lower dopant activation in SPE Si:C will offset the performance gain due to strain effect, especially for aggressively scaled n-MOSFETs. This problem can be mitigated with the use of PLA that allows for improved dopant activation in Si:C samples.…”

Section: Resultsmentioning

confidence: 99%

Silicon-Carbon Formed Using Cluster-Carbon Implant and Laser-Induced Epitaxy for Application as Source/Drain Stressors in Strained n-Channel MOSFETs

Koh

Wang

Sekar³

et al. 2009

J. Electrochem. Soc.

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Supersaturated and metastable silicon-carbon (Si:C) source/drain (S/D) stressors produced by laser anneal allow strain engineering for device performance enhancement. We report the use of a cluster-carbon (normalC7normalH7+) implant and pulsed excimer laser-induced epitaxial crystallization technique to form embedded Si:C S/D stressors with substitutional carbon concentration Csub of ∼1.1% . Transmission electron microscopy, secondary-ion mass spectrometry, and high resolution X-ray diffraction is used to characterize the structure and composition. n-field effect transistors (FETs) integrated with embedded Si:C S/D stressors formed using the normalC7normalH7+ implant and pulsed laser anneal technique demonstrate improvement in Ioff-IDSAT performance of ∼16% over control n-FETs formed without carbon implant at an Ioff=1×10−7A∕μm . Cluster–Carbon implant and laser anneal presented in this work is a simple and cost-effective approach to boost IDSAT performance and is a promising option for strain-engineering in advanced technology nodes.

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Codoping as a measure against donor deactivation in Si:Ab initiocalculations

Cited by 6 publications

References 27 publications

Silicon Single Crystal Growth from a Melt: On the Impact of Dopants on thev/GCriterion

Silicon Single Crystal Growth from a Melt: On the Impact of Dopants on thev/GCriterion

The Impact of Dopant Segregation on the Maximum Carrier Density in Si:P Multilayers

Silicon-Carbon Formed Using Cluster-Carbon Implant and Laser-Induced Epitaxy for Application as Source/Drain Stressors in Strained n-Channel MOSFETs

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