Lifetime recovery in ultrahighly titanium-doped silicon for the implementation of an intermediate band material

Antolín, E.; Martı́, Antonio; Olea, J.; Pastor, David; González-Dı́az, G.; Mártil, I.; Ĺuque, A.

doi:10.1063/1.3077202

Cited by 127 publications

(83 citation statements)

References 19 publications

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“…16 2 show the sheet resistance and Hall mobility, respectively, as a function of the absolute temperature (90-380 K) for the three different implantation doses and a nonimplanted substrate that will act as reference. The figures also include the fitting curves resulting from the model that will be described in Sec.…”

Section: Methodsmentioning

confidence: 99%

Two-layer Hall effect model for intermediate band Ti-implanted silicon

Olea

González-Dı́az

Pastor

et al. 2011

Journal of Applied Physics

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Si samples have been implanted with very high Ti doses (over the theoretical Mott limit) to obtain an intermediate band (IB) in the host semiconductor. The electronic transport properties of this material have been analyzed by temperature-dependent sheet resistance and Hall effect measurements in the 7-400 K range. The experimental results are successfully explained by means of an analytical two-layer model, in which the implanted layer and the substrate behave as an IB/ n-Si type junction. We deduce that the IB is located at 0.38 eV below the conduction band, which is around one third of the Si bandgap, i.e., theoretically close to the optimum location for an IB. Finally, we obtain that carriers at the IB behave as holes with a mobility of 0.4-0.6 cm 2 V À1 s À1 . This extremely low mobility is the one expected for a semifilled, metallic band, being this metallic condition of the IB a requirement for IB solar cells.

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Section: Methodsmentioning

confidence: 99%

Two-layer Hall effect model for intermediate band Ti-implanted silicon

Olea

González-Dı́az

Pastor

et al. 2011

Journal of Applied Physics

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“…However, experiments have shown that implanting larger doses of titanium in silicon results in lower SRH recombination 44 .…”

Section: Bulk Ib Materials and Solar Cellsmentioning

confidence: 99%

Understanding intermediate-band solar cells

2012

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The intermediate-band solar cell is designed to provide a large photogenerated current while maintaining a high output voltage. To make this possible, these cells incorporate an energy band that is partially filled with electrons within the forbidden bandgap of a semiconductor. Photons with insufficient energy to pump electrons from the valence band to the conduction band can use this intermediate band as a stepping stone to generate an electron-hole pair. Nanostructured materials and certain alloys have been employed in the practical implementation of intermediate-band solar cells, although challenges still remain for realizing practical devices. Here we offer our present understanding of intermediate-band solar cells, as well as a review of the different approaches pursed for their practical implementation. We also discuss how best to resolve the remaining technical issues.T he intermediate-band (IB) solar cell consists of an IB material sandwiched between two ordinary n-and p-type semiconductors 1 , which act as selective contacts to the conduction band (CB) and valence band (VB), respectively (Fig. la). In an IB material, sub-bandgap energy photons are absorbed through transitions from the VB to the IB and from the IB to the CB, which together add up to the current of conventional photons absorbed through the VB-CB transition. In 1997 2 , researchers used hypotheses similar to those adopted by Shockley and Queisser in 1961 3 to derive a detailed balance-limiting efficiency of 63% for the IB solar cell, at isotropic sunlight illumination (concentration of 46,050 suns) and assuming Sun and Earth temperatures to be 6,000 K and 300 K, respectively (Fig. lb). This work also presented the Shockley-Queisser limiting efficiency of 41% for single-gap solar cells operating under the same conditions 2 . The limiting efficiency of the IB solar cell is similar to that of a triple-junction solar cell connected in series. However, the IB can be regarded 4 as a set of two cells connected in series (corresponding to the VB-IB and IB-CB transitions) and one in parallel (corresponding to the VB-CB transition). This provides the IB solar cell with additional tolerance to changes in the solar spectrum.An optimal IB solar cellhas a total bandgap of about 1.95 eV, which is split by the IB into two sub-bandgaps of approximately 0.71 eV and 1.24 eV The quasi-Fermi levels (QFLs) or electrochemical potentials of the electrons in the different bands are usually close to the edges of the bands. Because the voltage of any solar cell is the difference between the CB QFL at the electrode in contact with the n-type side and the VB QFL at the electrode in contact with the p-type side, the maximum photovoltage of the IB solar cell is limited to 1.95 eV, although it is still capable of absorbing photons of energy above 0.71 eV In contrast, single-gap solar cells cannot supply a voltage greater than the lowest photon energy they can absorb. IB solar cells can deliver a high photovoltage by absorbing two subbandgap photons to produce one high ...

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“…In this way, the laser thermal annealing ͑LTA͒ process could be a technological key to obtain an IB in bulk semiconductors. 10,[14][15][16] The effect of the LTA process on III-V semiconductors has been reported previously. 17 However, as far as we are concerned no detailed study has been carried out on GaP.…”

Section: Introductionmentioning

confidence: 99%

Laser thermal annealing effects on single crystal gallium phosphide

Pastor¹,

Olea²,

Toledano-Luque³

et al. 2009

Journal of Applied Physics

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We have studied the laser thermal annealing ͑LTA͒ effects on single crystal GaP. The samples have been analyzed by means of Raman spectroscopy, glancing incidence x-ray diffraction ͑GIRXD͒, and transmission electron microscopy ͑TEM͒ measurements. After LTA process, the Raman spectra of samples annealed with the highest energy density show a forbidden TO vibrational mode of GaP. This result suggests the formation of crystalline domains with a different orientation in the annealed region regarding the GaP unannealed wafer. This behavior has been corroborated by GIXRD measurements. TEM images show that the LTA produces a defective layer with disoriented crystalline domains in the surface. The depth of this defective layer increases with the energy density of LTA. The lack of crystallinity after LTA processes could be related with the high bond energy value of GaP.

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Lifetime recovery in ultrahighly titanium-doped silicon for the implementation of an intermediate band material

Cited by 127 publications

References 19 publications

Two-layer Hall effect model for intermediate band Ti-implanted silicon

Two-layer Hall effect model for intermediate band Ti-implanted silicon

Understanding intermediate-band solar cells

Laser thermal annealing effects on single crystal gallium phosphide

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