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CRUE-CSIC (Acuerdos Transformativos 2022) "Authors would like to acknowledge C.A.I. de Técnicas Físicas of the Universidad Complutense de Madrid for ion implantation, and the technical. This work was partially supported by the Project MADRIDPV2 (Grant No. P20138/EMT-4308) funded by the Comunidad Autónoma de Madrid with the support of FEDER funds, by the Spanish MINECO (Ministerio de Economía y Competitividad) under grants PID2020-116508RB-100, PID2020-117498RB-I00 and RTI2018-096498-B-I00. One of the authors (S. Algaidy) would also like to acknowledge financial support from Ministry of Education in the Kingdom of Saudi Arabia. D.Caudevilla would also like to acknowledge a grant (PRE2018-083798), financed by MICINN and European Social Fund. F. Perez-Zenteno would like to acknowledge financial support Mexico grant program CONACyT under grant 786327. The authors would like to also acknowledge the services of CAI de Espectroscopia of UCM, (INA-LMA) de Universidad de Zaragoza and C.A.C.T.I de Universidad de Vigo for Raman, FIB-SEM and SIMS, respectively.", We present a detailed investigation on the formation of supersaturated GaAs using Ti+ implantation followed by nanosecond Pulsed Laser Melting (PLM). We have synthesized high-crystal quality supersaturated GaAs layers with concentrations of Ti above the insulator to metal transition (Mott limit). The Ti-implanted concentration depth profiles after PLM obtained by Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) show a redistribution of Ti impurities within the first hundred nanometers and superficial concentration up to 1 × 1021 redistrcm-3. Raman spectroscopy of these Ti supersaturated, and regrown GaAs samples shows a sharp crystalline peak and tensile strain due to the Ti lattice incorporation. Scanning Transmission Electron Microscopy (STEM) and high-resolution Transmission Electron Microscopy (TEM) images show a good GaAs crystallinity after the PLM process. Energy-Dispersive X-ray Spectroscopy (EDS) reveals an enhanced Ti signal inside bubble-like structures and an appearance of interface oxide layer with all processed samples., Ministerio de Ciencia e Innovación (MICINN)/FEDER, Comunidad de Madrid/ FEDER, Ministerio de Economía y Competitividad (MINECO), Ministry of Education of Saudi Arabia, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Microwave annealing (MWA) processes were used for the first time to obtain Ti supersaturated Si. High Ti doses were ion implanted on Si substrates and subsequently MWA processed to recrystallize the amorphous layer. The resulting layers were monocrystalline with a high density of defects. Ti depth profiles indicate that diffusion is avoided once recrystallization is produced. Finally, the electronic transport properties measurements point to a decoupling effect between the Si:Ti layer and the substrate. The implanted layer present also a shallow donor and very high Hall mobility., Universidad Complutense de Madrid, European Regional Development Fund (Unión Europea), Ministerio de Ciencia e Innovación (España), European Social Found (Unión Europea), Ministry of Education (Arabia Saudita), Consejo Nacional de Humanidades, Ciencias y Tecnologías (México), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

In this article, we study the effect of the inversion charge ( Q _inv ) in a solar cell based on the hole-selective characteristic of substoichiometric molybdenum oxide (MoO_x ) and vanadium oxide (VO_x ) deposited directly on n-type silicon. We measure the capacitance–voltage ( C – V ) curves of the solar cells at different frequencies and explain the results taking into account the variation of the space charge and the existence of Q_inv in the c-Si inverted region. The high-frequency capacitance measurements follow the Schottky metal–semiconductor theory, pointing to a low inversion charge influence in these measurements. However, for frequencies lower than 20 kHz, an increase in the capacitance is observed, which we relate to the contribution of the inversion charge. In addition, applying the metal–semiconductor theory to the high-frequency measurements, we have obtained the built-in voltage potential and show new evidence about the nature of the conduction process in this structure. This article provides a better understanding of the transition metal oxide/n-type crystalline silicon heterocontact., Comunidad de Madrid, Fondo Europeo de Desarrollo Regional (Unión Europea), Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), European Social Fund (Unión Europea), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Hyperdoped or supersaturated semiconductors are gathering the attention of industry and research institutions due to their sub-bandgap photon absorption properties. In this study, two fast and non-invasive techniques, time-resolved reflectometry (TRR) and Haze Measurements, are applied to infer the melt and solidification regimes of Ti supersaturated 300 mm silicon wafers, aiming to ease the characterization process towards high volume manufacturing of supersaturated materials. Ti supersaturation is attained by using an ion implantation process with a dose 3 x 10(15) cm(-2), which amorphizes the surface. Crystalline quality is then recovered by means of a XeCl UV nanosecond laser annealing process. TRR technique is used to determine two different melting and solidification processes of the laser annealed implanted surface. A first brief, low temperature peak (alpha peak) is associated with the melting process of the amorphized surface, followed by a longer peak/plateau (beta (1) peak/plateau), linked to the melting process of the crystalline phase below the amorphized layer, at sufficiently high laser fluences. Haze technique is used to indirectly measure the crystalline quality after the solidification process of the laser-annealed surface. Atomic force microscopy measurements are used to obtain the surface roughness value and cross-section high resolution transmission electron microscopy micrographs to check crystalline quality., Ministerio de Ciencia e Innovación (España), Comunidad de Madrid, Ministerio de Economia y Competitividad (España), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© AIP Publishing LLC. The authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantations and metallic evaporations. This work was partially supported by the Project NUMANCIA II (Grant No. S-2009/ENE/1477) funded by the Comunidad de Madrid. Research by E. Garca-Hemme was also supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). J. Olea and D. Pastor thank Professor A. Mart_ı and Professor A. Luque for useful discussions and guidance and acknowledge financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402 and JCI-2011-11471), under which this research was undertaken., We report room-temperature operation of 1 x 1 cm(2) infrared photoconductive photodetectors based on silicon supersaturated with titanium. We have fabricated these Si-based infrared photodetectors devices by means of ion implantation followed by a pulsed laser melting process. A high sub-band gap responsivity of 34 mVW(-1) has been obtained operating at the useful telecommunication applications wavelength of 1.55 mu m (0.8 eV). The sub-band gap responsivity shows a cut-off frequency as high as 1.9 kHz. These Si-based devices exhibit a non-previous reported specific detectivity of 1.7 x 10(4) cm Hz(1/2) W-1 at 660Hz, under a 1.55 mu m wavelength light. This work shows the potential of Ti supersaturated Si as a fully CMOS-compatible material for the infrared photodetection technology., Comunidad de Madrid, Moncloa Campus of International Excellence (UCM-UPM), MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 IOP Publishing Ltd. Authors would like to acknowledge the CAI de Técnicas Físicas and C.A.I de Espectroscopía of the Universidad Complutense de Madrid for the use of its laboratories and FTIR measurements. This work was partially supported by the Project MADRID-PV (Grant No. 2013/MAE-2780) funded by the Comunidad de Madrid, by the Spanish MINECO (Ministerio de economía y competitividad) under grant TEC 2013-41730-R and by the Universidad Complutense de Madrid (Programa de Financiación de Grupos de Investigación UCM–Banco Santander) under grant 910173-2014. D. Montero acknowledges the Spanish MINECO (Ministerio de economía y competitividad) for financial support under contract BES-2014-067585, Amorphous silicon thin films were deposited using the high pressure sputtering (HPS) technique to study the influence of deposition parameters on film composition, presence of impurities, atomic bonding characteristics and optical properties. An optical emission spectroscopy (OES) system has been used to identify the different species present in the plasma in order to obtain appropriate conditions to deposit high purity films. Composition measurements in agreement with the OES information showed impurities which critically depend on the deposition rate and on the gas pressure. We prove that films deposited at the highest RF power and 3.4 × 10^−2 mbar, exhibit properties as good as the ones of the films deposited by other more standard techniques., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Programa de Financiación de Grupos de Investigación UCM–Banco Santander, Universidad Complutense de Madrid (UCM), Banco Santander Central Hispano (BSCH), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

©2015 IOP Publishing Ltd. Authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantations and metallic evaporations and to the Nanotechnology and Surface Analysis Services of the Universidad de Vigo C.A.C.T.I. for ToF-SIMS measurements. This work was partially supported by the Project MADRID-PV (Grant No. P2013/MAE-2780) funded by the Comunidad de Madrid and by the Spanish MINECO (Economic and Competitiviness Ministery) under grant TEC 2013-41730-R Research by E. García-Hemme was also supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). J. Olea thank Professor A. Martí and Professor A. Luque for useful discussions and guidance and acknowledge financial support from the MICINN within the program Juan de la Cierva (JCI- 2011-10402 and JCI-2011-11471), under which this research was undertaken. D. Pastor acknowledges the financial support to the grant EX-2010-0662 from the Spanish Science Ministry., This paper presents the results for the transverse conductance across a bilayer formed by supersaturating with diverse transition metals a thin layer of a silicon wafer. The layer is formed by ion implantation and annealed by pulsed laser melting. The transverse conductance is exponentially activated, obtaining values ranging from 0.018 to 0.7 eV for the activation energy and pre-exponential factors of 10^-2-10^12 S depending on the annealing energy density. A semi-logarithmic plot of the pre-exponential factor versus activation energy shows an almost perfect linear behavior as stated by the Meyer Neldel rule. The Meyer Neldel energy obtained for implantation with different transition metals and also annealed in different conditions is 22meV, which is within the range of silicon phonons, thus confirming the hypothesis of the Multi Excitation Entropy theory., Comunidad de Madrid, Ministerio de Economía y Competitividad (MINECO), España, Programa MADRID-PV, Programa Internacional de Captación de Talento (PICATA ), CEI-Moncloa, Campus de Excelencia Internacional (CEI) Moncloa, Programa Juan de la Cierva, Ministerio de Ciencia e Innovación (MICINN), España, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 IOP Publishing Ltd. The authors would like to acknowledge the C A I de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantations and metallic evaporations, the Nanotechnology and Surface Analysis Services of the Universidad de Vigo C.A.C.T.I. for ToF-SIMS measurements and Dr J P González García from CIEMAT for reflectance measurements. Research by E García-Hemme was supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). J Olea acknowledges financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402), under which this research was undertaken. D Pastor acknowledges the financial support to the grant EX-2010-0662 from the Spanish Science Ministry. This work was partially supported by the Spanish MINECO (Economic and Competitiviness Ministery) through grant TEC 2013-41730-R. The authors acknowledge the financial support from la Comunidad de Madrid throughout the funding of the project, MADRID-PV (S2013/MAE-2780)., Silicon samples were implanted with high Ti doses and subsequently processed with the pulsed-laser melting technique. The electronic transport properties in the 15–300 K range and the room temperature spectral photoresponse at energies over the bandgap were measured. Samples with Ti concentration below the insulator-metal (I-M) transition limit showed a progressive reduction of the carrier lifetime in the implanted layer as Ti dose is increased. However, when the Ti concentration exceeded this limit, an extraordinary recovery of the photoresponse was measured. This result supports the theory of intermediate band materials and is of utmost relevance for photovoltaic cells and Si-based detectors., Ministerio de Economía y Competitividad (MINECO), Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid, Campus de Excelencia Internacional Moncloa UCM-UPM, PICATA Programa Internacional de Captación de Talento Convocatorias Campus Moncloa, Ayudas para contratos Juan de la Cierva (MICINN), Ministerio de Ciencia y Tecnología (MCYT), España, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 AIP Publishing LLC. The study has been supported by the Spanish TEC2014 under Grant No. 52152-C3-3-R, TEC2013 41730-R funded by the Ministerio de Economía y Competitividad, and the P2013/MAE-2780 funded by the Comunidad de Madrid. Research of E. Pérez was supported by a University of Valladolid FPI Grant. J. Olea acknowledges financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402), under which this research was undertaken. Research by E. García-Hemme was also supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM)., The energy levels created in supersaturated n-type silicon substrates with titanium implantation in the attempt to create an intermediate band in their band-gap are studied in detail. Two titanium ion implantation doses (1013 cm-2 and 1014 cm-2) are studied in this work by conductance transient technique and admittance spectroscopy. Conductance transients have been measured at temperatures of around 100 K. The particular shape of these transients is due to the formation of energy barriers in the conduction band, as a consequence of the band-gap narrowing induced by the high titanium concentration. Moreover, stationary admittance spectroscopy results suggest the existence of different energy level configuration, depending on the local titanium concentration. A continuum energy level band is formed when titanium concentration is over the Mott limit. On the other hand, when titanium concentration is lower than the Mott limit, but much higher than the donor impurity density, a quasi-continuum energy level distribution appears. Finally, a single deep center appears for low titanium concentration. At the n-type substrate, the experimental results obtained by means of thermal admittance spectroscopy at high reverse bias reveal the presence of single levels located at around Ec-425 and Ec-275 meV for implantation doses of 1013 cm2 and 1014 cm2, respectively. At low reverse bias voltage, quasi continuously distributed energy levels between the minimum of the conduction bands, Ec and Ec-450 meV, are obtained for both doses. Conductance transients detected at low temperatures reveal that the high impurity concentration induces a band gap narrowing which leads to the formation of a barrier in the conduction band. Besides, the relationship between the activation energy and the capture cross section values of all the energy levels fits very well to the Meyer-Neldel rule. As it is known, the Meyer Neldel rule typically appears in processes involving multiple excitations, like carr, Comunidad de Madrid, Spanish TEC2014, Ministerio de Economía y Competitividad (MINECO), University of Valladolid, Ministerio de Ciencia e Innovación (MICINN), Moncloa Campus of International Excellence (UCM-UPM)., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Institute of Physics. Authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantations and metallic evaporations and the Nanotechnology and Surface Analysis Services of the Universidad de Vigo C.A.C.T.I. for ToF-SIMS measurements. This work was partially supported by the Project NUMANCIA II (Grant No. S-2009/ENE/1477) funded by the Comunidad de Madrid. Research by E. García-Hemme was also supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). J. Olea and D. Pastor thanks Professor A. Martí and Professor A. Luque for useful discussions and guidance and acknowledge financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402 and JCI-2011-11471), under which this research was undertaken., We have analyzed the increase of the sheet conductance (Delta G(square)) under spectral illumination in high dose Ti implanted Si samples subsequently processed by pulsed-laser melting. Samples with Ti concentration clearly above the insulator-metal transition limit show a remarkably high Delta G(square), even higher than that measured in a silicon reference sample. This increase in the Delta G(square) magnitude is contrary to the classic understanding of recombination centers action and supports the lifetime recovery predicted for concentrations of deep levels above the insulator-metal transition., Comunidad de Madrid, MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 The Author(s). The study has been supported by the Spanish TEC2014 under Grant Nos. 52152-C3-3-R and TEC2013-41730-R, funded by the Ministerio de Economía y Competitividad, and the P2013/MAE-2780 funded by the Comunidad de Madrid., A complete electrical characterization of hydrogenated amorphous silicon layers (a-Si:H) deposited on crystalline silicon (c-Si) substrates by electron cyclotron resonance chemical vapor deposition (ECR-CVD) was carried out. These structures are of interest for photovoltaic applications. Different growth temperatures between 30 and 200 °C were used. A rapid thermal annealing in forming gas atmosphere at 200 °C during 10 min was applied after the metallization process. The evolution of interfacial state density with the deposition temperature indicates a better interface passivation at higher growth temperatures. However, in these cases, an important contribution of slow states is detected as well. Thus, using intermediate growth temperatures (100–150 °C) might be the best choice., Spanish TEC2014 Ministerio de Economía y Competitividad, Comunidad de Madrid, Spain, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 Elsevier B.V. Authors would like to acknowledge the C.A.I. de Técnicas Físicas of the Universidad Complutense de Madrid for ion implantation experiments and the Nanotechnology and Surface Analysis Services of the Universidad de Vigo C.A.C.T.I. for ToF-SIMS measurements. This work was partially supported by the Projects GENESIS-FV (CSD2006-0004) funded by the Spanish Consolider National Programme, NUMANCIA II (S-2009/ENE-1477) funded by the Regional Government of Comunidad de Madrid and grant GR58/08 funded by the Universidad Complutense de Madrid., Si samples implanted with very high Ti doses and subjected to Pulsed-Laser Melting (PLM) have been electrically analyzed in the scope of a two-layer model previously reported based on the Intermediate Band (IB) theory. Conductivity and Hall effect measurements using the van der Pauw technique suggest that the insulator-metal transition takes place for implantation doses in the 10(14)-10(16) cm(-2) range. Results of the sample implanted with the 10(16) cm(-2) dose show a metallic behavior at low temperature that is explained by the formation of a p-type IB out of the Ti deep levels. This suggests that the IB would be semi-filled, which is essential for IB photovoltaic devices., Comunidad de Madrid, Spanish Consolider National Programme - Projects GENESIS-FV, Universidad Complutense de Madrid, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 AIP Publishing LLC. he authors would like to acknowledge the C.A.I. de Técnicas Físicas for ion implantation experiments and e-beam evaporations, the Nanotechnology and Surface Analysis Services of the Universidad de Vigo C.A.C.T.I. for ToF-SIMS measurements, Dr. J. Herrero (CIEMAT) for UVVIS-IR measurements facilities, and the Instituto de Nanociencia de Aragón for the TEM images. J. Olea and D. Pastor thanks Professor A. Martí and Professor A. Luque for useful discussions and guidance and acknowledge financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402 and JCI-2011-11471), under which this research was undertaken. Research by E. Garcìa-Hemme has been partly supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). This work was partially supported by the projects NUMANCIA II (S-2009/ENE-1477) founded by the Regional Government of Comunidad de Madrid and grant GR35/10-A founded by the Universidad Complutense de Madrid., In this study, we present a structural and optoelectronic characterization of high dose Ti implanted Si subsequently pulsed-laser melted (Ti supersaturated Si). Time-of-flight secondary ion mass spectrometry analysis reveals that the theoretical Mott limit has been surpassed after the laser process and transmission electron microscopy images show a good lattice reconstruction. Optical characterization shows strong sub-band gap absorption related to the high Ti concentration. Photoconductivity measurements show that Ti supersaturated Si presents spectral response orders of magnitude higher than unimplanted Si at energies below the band gap. We conclude that the observed below band gap photoconductivity cannot be attributed to structural defects produced by the fabrication processes and suggest that both absorption coefficient of the new material and lifetime of photoexcited carriers have been enhanced due to the presence of a high Ti concentration. This remarkable result proves that Ti supersaturated Si is a promising material for both infrared detectors and high efficiency photovoltaic devices., Comunidad de Madrid, MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 IOP Publishing Ltd. The authors would like to thank the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for ion implantations, metallic evaporations and measurements with the optical profilometer. This work was partially supported by the Project NUMANCIA II (Grant No S-2009/ENE/1477) funded by the Comunidad de Madrid. Research by E García-Hemme has been partly supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). DP and JO are grateful to Professors A Luque and A Martí for useful discussions and guidance and also acknowledge financial support from the MICINN within the program Juan de la Cierva (JCI-2011-10402 and JCI-2011-11471)., We investigated the electrical transport properties of ultraheavily Ti-implanted silicon layers subsequently pulsed laser melted (PLM). After PLM, the samples exhibit anomalous electrical behaviour in sheet resistance and Hall mobility measurements, which is associated with the formation of an intermediate band (IB) in the implanted layer. An analytical model that assumes IB formation and a current limitation effect between the implanted layer and the substrate was developed to analyse this anomalous behaviour. This model also describes the behaviour of the function V/Delta V and the electrical function F that can be extracted from the electrical measurements in the bilayer. After chemical etching of the implanted layer, the anomalous electrical behaviour observed in sheet resistance and Hall mobility measurements vanishes, recovering the unimplanted Si behaviour, in agreement with the analytical model. The behaviour of V/Delta V and the electrical function F can also be successfully described in terms of the analytical model in the bilayer structure with the implanted layer entirely stripped., Comunidad de Madrid, MICINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 IOP Publishing Ltd. Authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantation procees and metallic evaporations. This work was partially supported by the Project MADRID-PV (Grant No. 2013/MAE-2780) funded by the Comunidad de Madrid, by the Spanish MINECO (Economic and Competitiviness Ministery) under grant TEC 2013-41730-R and by the Universidad Complutense de Madrid (Programa de Financiación de Grupos de Investigación UCM-Banco Santander) under grant 910173-2014. D Montero acknowledge the Spanish MINECO (Economic and Competitiviness Ministery) for financial support under contract BES-2014-067585., We report the observation of the insulator-to-metal transition in crystalline silicon samples supersaturated with vanadium. Ion implantation followed by pulsed laser melting and rapid resolidification produce high quality single-crystalline silicon samples with vanadium concentrations that exceed equilibrium values in more than 5 orders of magnitude. Temperature-dependent analysis of the conductivity and Hall mobility values for temperatures from 10K to 300K indicate that a transition from an insulating to a metallic phase is obtained at a vanadium concentration between 1.1 × 10^(20) and 1.3 × 10^(21) cm^(−3) . Samples in the insulating phase present a variable-range hopping transport mechanism with a Coulomb gap at the Fermi energy level. Electron wave function localization length increases from 61 to 82 nm as the vanadium concentration increases in the films, supporting the theory of impurity band merging from delocalization of levels states. On the metallic phase, electronic transport present a dispersion mechanism related with the Kondo effect, suggesting the presence of local magnetic moments in the vanadium supersaturated silicon material., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Universidad Complutense de Madrid (Programa de Financiación de Grupos de Investigación UCM-Banco Santander), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 IEEE. This work was supported in part by the Project MADRID-PV (under Grant 2013/MAE-2780) funded by the Comunidad de Madrid, by the Spanish Ministerio de Economía y Competitividad (MINECO) under Grant TEC 2013-41730-R and Grant TEC2016-75099-R, and by the Universidad Complutense de Madrid (Programa de Financiación de Grupos de Investigación UCM–Banco Santander) under Grant 910173-2014. The work of D. Montero was supported by the Spanish MINECO under Contract BES-2014-067585., We have deposited intrinsic amorphous silicon (a-Si:H) using the electron cyclotron resonance (ECR) chemical vapor deposition technique in order to analyze the a-Si:H/c-Si heterointerface and assess the possible application in heterojunction with intrinsic thin layer (HIT) solar cells. Physical characterization of the deposited films shows that the hydrogen content is in the 15-30% range, depending on deposition temperature. The optical bandgap value is always comprised within the range 1.9- 2.2 eV. Minority carrier lifetime measurements performed on the heterostructures reach high values up to 1.3 ms, indicating a well-passivated a-Si:H/c-Si heterointerface for deposition temperatures as low as 100°C. In addition, we prove that the metal-oxide- semiconductor conductance method to obtain interface trap distribution can be applied to the a-Si:H/c-Si heterointerface, since the intrinsic a-Si:H layer behaves as an insulator at low or negative bias. Values for the minimum of D_it as low as 8 × 10^10 cm^2 · eV^-1 were obtained for our samples, pointing to good surface passivation properties of ECR-deposited a-Si:H for HIT solar cell applications., Ministerio de Economía y Competitividad (MINECO), España, Comunidad de Madrid, Programa de Financiación de Grupos de Investigación UCM–Banco Santander, Universidad Complutense de Madrid (UCM), Banco Santander Central Hispano (BSCH), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Una de las principales herramientas para la creación de circuitos son los transistores. Estos dispositivos electrónicos actúan como interruptores controlados eléctricamente que permiten la creación de circuitos lógicos que pueden operar con señales de "1" y "0". Los transistores se han convertido en una pieza fundamental para la creación de la tecnología digital moderna, y su presencia es imprescindible en una gran cantidad de dispositivos electrónicos, desde microprocesadores hasta sensores. En este trabajo de fin de grado, se profundizará en el estudio de los transistores, abarcando desde su funcionamiento básico hasta su aplicación en circuitos digitales complejos de memorias SRAM. Se explicará en detalle cómo los transistores permiten la manipulación de las señales eléctricas y cómo se pueden utilizar para la creación de dispositivos lógicos simples y complejos. También se analizarán las características de los diferentes tipos de transistores, como los MOSFETs, y se explorará su uso en circuitos integrados y otros dispositivos electrónicos avanzados. El objetivo final de este trabajo es proporcionar una comprensión sólida de los transistores, así como su aplicación y funcionamiento en el diseño de circuitos electrónicos de memorias SRAM. Además, se espera que este trabajo sirva como una base sólida para futuros estudios en electrónica y tecnología de la información., One of the main tools for creating circuits are transistors. These electronic devices act as electrically controlled switches allowing the creation of logic circuits that can operate with binary signals. Transistors have become a undamental part of the creation of modern digital technology, and their presence is essential in many electronic devices, from microprocessors to sensors. In this BSc thesis, transistors will be studied in depth, ranging from its basic operation to its application in complex digital circuits of SRAM memories. It will be explained in detail how transistors allow for the manipulation of electrical signals and how they can be used to create simple and complex logic devices. The characteristics of different types of transistors, such as MOSFETs, will also be analyzed, and their use in integrated circuits and other advanced electronic devices will be explored. The goal of this work is to provide a solid understanding of transistors, as well as their application and operation in the design of electronic circuits for SRAM memories. Furthermore, it is hoped that this work will serve as a solid foundation for future studies in electronics and information technology.

© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., In this article, we study the effect of the inversion charge ( Q inv ) in a solar cell based on the hole-selective characteristic of substoichiometric molybdenum oxide (MoO x ) and vanadium oxide (VO x ) deposited directly on n-type silicon. We measure the capacitance–voltage ( C – V ) curves of the solar cells at different frequencies and explain the results taking into account the variation of the space charge and the existence of Q inv in the c-Si inverted region. The high-frequency capacitance measurements follow the Schottky metal–semiconductor theory, pointing to a low inversion charge influence in these measurements. However, for frequencies lower than 20 kHz, an increase in the capacitance is observed, which we relate to the contribution of the inversion charge. In addition, applying the metal–semiconductor theory to the high-frequency measurements, we have obtained the built-in voltage potential and show new evidence about the nature of the conduction process in this structure. This article provides a better understanding of the transition metal oxide/n-type crystalline silicon heterocontact., The authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid. The authors would also like to thank the Mexican grants program CONACyT for its financial collaboration., Peer Reviewed, Postprint (author's final draft)

Artículo firmado por 15 autores. © 2022 IOP Publishing Ltd. The authors would like to thank the Physical Sciences Research Assistance Centre (CAI de Técnicas Físicas) of the Complutense University of Madrid. This study was partially funded by Project MADRID-PV2 (P2018/EMT-4308), with aid from the Regional Government of Madrid and the ERDF, by the Spanish Ministry of Science and Innovation/National Research Agency (MCIN/AEI) under Grants TEC2017- 84378-R, PID2019-109215RB-C41, PID2020-116508RB-I00 and PID2020-117498RB-I00. Daniel Caudevilla would like to express his thanks for Grant PRE2018-083798, provided by the MICINN and the European Social Fund. Francisco Pérez Zenteno would also like to express his thanks for Grant 984933, provided by CONACyT (Mexico)., According to intermediate band (IB) theory, it is possible to increase the efficiency of a solar cell by boosting its ability to absorb low-energy photons. In this study, we used a hyperdoped semiconductor approach for this theory to create a proof of concept of different silicon-based IB solar cells. Preliminary results show an increase in the external quantum efficiency (EQE) in the silicon sub-bandgap region. This result points to sub-bandgap absorption in silicon having not only a direct application in solar cells but also in other areas such as infrared photodetectors. To establish the transport mechanisms in the hyperdoped semiconductors within a solar cell, we measured the J-V characteristic at different temperatures. We carried out the measurements in both dark and illuminated conditions. To explain the behavior of the measurements, we proposed a new model with three elements for the IB solar cell. This model is similar to the classic two-diodes solar cell model but it is necessary to include a new limiting current element in series with one of the diodes. The proposed model is also compatible with an impurity band formation within silicon bandgap. At high temperatures, the distance between the IB and the n-type amorphous silicon conduction band is close enough and both bands are contacted. As the temperature decreases, the distance between the bands increases and therefore this process becomes more limiting., Project MADRID-PV2, Regional Government of Madrid, ERDF, Spanish Ministry of Science and Innovation/National Research Agency (MCIN/AEI), Ministerio de Ciencia e Innovación, European Social Fund, CONACyT (Mexico), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2022 IOP Publishing Ltd. Authors wish to acknowledge assistance from CAI de Técnicas Físicas (Unidad de Implantación Iónica) and CAI de Técnicas Químicas (Espectroscopía Raman y Correlación) from the Universidad Complutense de Madrid with the Ion Implantations and Raman measurements, respectively. We also acknowledge Servicio de Nanotecnología y Análisis de Superficies del CACTI de la Universidad de Vigo for ToF-SIMS measurements and ICTS-CNM from Madrid for the SEM images. This work was partially supported by the Projects MADRID-PV2 (P2018/EMT-4308) funded by the Comunidad Autónoma de Madrid with the support from FEDER Funds and Projects SCCell (PID2020-116508RB-I00), HyperPHIR (PID2020-117498RB-I00) and SCALED (PID2019-109215RB-C42), funded by the Spanish Ministry of Science and Innovation. D Caudevilla would also acknowledge the Grant PRE2018-083798, financed by MICINN and European Social Fund. F Pérez-Zenteno would also like to acknowledge Grant 786327 form Mexican grants program CONACyT., In this work we have successfully hyperdoped germanium with tellurium with a concentration peak of 10(21) cm(-3). The resulting hyperdoped layers show good crystallinity and sub-bandgap absorption at room temperature which makes the material a good candidate for a new era of complementary metal-oxide-semiconductor-compatible short-wavelength-infrared photodetectors. We obtained absorption coefficients ci higher than 4.1 x 10(3) cm(-1) at least up to 3 mu m. In this study we report the temperature-dependency electrical properties of the hyperdoped layer measured in van der Pauw configuration. The electrical behaviour of this hyperdoped material can be explained with an electrical bilayer coupling/decoupling model and the values for the isolated hyperdoped layer are a resistivity of 4.25 x 10(-3) Omega.cm with an electron-mobility around -100 cm(2) V-1 s(-1)., Ministerio de Ciencia e innovación (MICINN)., Ministerio de Ciencia e Innovación (MICINN)/FEDER, Comunidad de Madrid/ FEDER, Mexican grants program CONACyT, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2021) The authors acknowledge the "CAI de Tecnicas Fisicas", the "CAI de Difraccion de Rayos X '' of Universidad Complutense de Madrid, and "Laboratorio de Caracterizacion de Superficies" of CENIM for sample fabrication, GIXRD and XPS measurements, respectively. Also we acknowledge J. Gandia for his support in the analysis of the optical measurements. This work is part of the project MADRID-PV2 (P2018/EMT-4308) funded by the Comunidad Autonoma de Madrid with the support from FEDER Funds, project TEC2017-84378-R, funded by MICINN and European Social Fund, and projects SCCell (PID2020-116508RB-I00) , HyperPHIR (PID2020-117498RB-I00) and SCALED (PID2019-109215RB-C42) , funded by the Spanish Ministry of Science and Innovation. D.Pastor acknowledges financial support from the MEC to the program Ramon y Cajal (No. RYC-2014-16936) . D. Caudevilla would also acknowledge grant PRE2018-083798, financed by MICINN and European Social Fund., This article studies the physical and electrical behavior of indium tin oxide layers (ITO) grown by an unconventional technique: High Pressure Sputtering (HPS), from a ceramic ITO target in a pure Ar atmosphere. This technique has the potential to reduce plasma induced damage to the samples. The aim is to obtain, at low temperature via HPS, good quality transparent conductive oxide layers for experimental photovoltaic cells with emerging selective contacts such as transition metal oxides, alkaline metal fluorides, etc. We found that the resistivity of the films was strongly dependent on Ar pressure. To obtain device-quality resistivity without intentional heating during deposition a pressure higher than 1.0 mbar was needed. These films deposited on glass were amorphous, presented a high electron mobility (up to 45 cm2V- 1s- 1) and a high carrier density (2.9 x 1020 cm-3 for the sample with the highest mobility). The optimum Ar pressure range was found at 1.5-2.3 mbar. However, the resistivity degraded with a moderate annealing temperature in air. Finally, the feasibility of the integration with photovoltaic cells was assessed by depositing on Si substrates passivated by a-Si:H. The film deposited at 1.5 mbar was uniform and amorphous, and the carrier lifetime obtained was 1.22 ms with an implied open circuit voltage of 719 mV after a 215 degrees C air anneal. The antireflective properties of HPS ITO were also demonstrated. These results show that ITO deposited by HPS is adequate for the research of solar cells with emerging selective contacts., Ministerio de Ciencia e Innovación (MICINN)/ESF, Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid/FEDER, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Se deposita la versión posprint del artículo, In the scope of supersaturated semiconductors for infrared detectors, we implanted Si samples with Ti at high doses and processed them by rapid thermal annealing (RTA) to recover the crystal quality. Also, for comparative purposes, some samples were processed by pulsed-laser melting. We measured the electronic transport properties at variable temperatures and analyzed the results. The results indicate that, for RTA samples, surface layers with a high Ti concentration have negligible conductivity due to defects. In contrast, the implantation tail region has measurable conductivity due to very high electron mobility. This region shows the activation of a very shallow donor and a deep donor level. While deep levels have been previously reported for Ti in Si, such a shallow level has never been measured, and we suggest that it originates from Ti-Si complexes. Finally, a decoupling effect between the implanted layer and the substrate seems to be present, and a bilayer model is applied to fit the measured properties. The fitted parameters follow the Meyer–Neldel rule. The role of the implantation tails in Si supersaturated with Ti is revealed in this work., Comunidad de Madrid, ERDF Funds - MICINN, European Social Fund (ESF), Ministerio de Ciencia e Innovación (España), Mexican grants program CONACyT, Ministry of Education in the Kingdom of Saudi Arabia, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Authors would like to acknowledge the technical and human support provided by Facility of Analysis and Characterization of Solids and Surfaces of SAIUEx (financed by UEX, Junta de Extremadura, MICINN, FEDER and FSE), as well as the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the ion implantation and rapid thermal annealing processes, and the ICTS Centro Nacional de Microscopia Electrónica for the microstructural measurements. The authors would like to thank Sven Kayser from IONTOF GmbH (Germany) for his helpful discussion about the dual beam configuration and ion beam mixing artefact. This work was partially supported by the Project MADRID-PV2 (P2018/EMT-4308) funded by the Regional Government of Madrid with the support from the European Regional Development Fund (ERDF), by the Spanish MINECO (Ministerio de Economía y Competitividad) under grants TEC2017-84378-R, PID2020-116508RB-I00, and PID2020-117498RB-I00. Daniel Caudevilla would also acknowledge the grant PRE2018-083798, financed by MICINN and European Social Fund. The authors are also thankful for financial collaboration from the Mexican grants program CONACyT., This work deepens the understanding of the optoelectronic mechanisms ruling hyperdoped-based photodevices and shows the potential of Ti hyperdoped-Si as a fully complementary metal-oxide semiconductor compatible material for room-temperature infrared photodetection technologies. By the combination of ion implantation and laser-based methods, approximate to 20 nm thin hyperdoped single-crystal Si layers with a Ti concentration as high as 10(20) cm(-3) are obtained. The Ti hyperdoped Si/p-Si photodiode shows a room temperature rectification factor at +/- 1 V of 509. Analysis of the temperature-dependent current-voltage characteristics shows that the transport is dominated by two mechanisms: a tunnel mechanism at low bias and a recombination process in the space charge region at high bias. A room-temperature sub-bandgap external quantum efficiency (EQE) extending to 2.5 mu m wavelength is obtained. Temperature-dependent spectral photoresponse behavior reveals an increase of the EQE as the temperature decreases, showing a low-energy photoresponse edge at 0.45 eV and a high-energy photoresponse edge at 0.67 eV. Temperature behavior of the open-circuit voltage correlates with the high-energy photoresponse edge. A model is proposed to relate the optoelectronic mechanisms to sub-bandgap optical transitions involving an impurity band. This model is supported by numerical semiconductor device simulations using the SCAPS software., MADRID-PV2 - Regional Government of Madrid, European Regional Development Fund (ERDF), Ministerio de Economía y Competitividad (MINECO), MICINN, European Social Fund, CONACyT, UEX, Junta de Extremadura, FEDER, FSE, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

According to intermediate band (IB) theory, it is possible to increase the efficiency of a solar cell by boosting its ability to absorb low-energy photons. In this study, we used a hyperdoped semiconductor approach for this theory to create a proof of concept of different silicon-based IB solar cells. Preliminary results show an increase in the external quantum efficiency (EQE) in the silicon sub-bandgap region. This result points to sub-bandgap absorption in silicon having not only a direct application in solar cells but also in other areas such as infrared photodetectors. To establish the transport mechanisms in the hyperdoped semiconductors within a solar cell, we measured the J–V characteristic at different temperatures. We carried out the measurements in both dark and illuminated conditions. To explain the behavior of the measurements, we proposed a new model with three elements for the IB solar cell. This model is similar to the classic two-diodes solar cell model but it is necessary to include a new limiting current element in series with one of the diodes. The proposed model is also compatible with an impurity band formation within silicon bandgap. At high temperatures, the distance between the IB and the n-type amorphous silicon conduction band is close enough and both bands are contacted. As the temperature decreases, the distance between the bands increases and therefore this process becomes more limiting., The authors would like to thank the Physical Sciences Research Assistance Centre (CAI de Técnicas Físicas) of the Complutense University of Madrid. This study was partially funded by Project MADRID-PV2 (P2018/EMT-4308), with aid from the Regional Government of Madrid and the ERDF, by the Spanish Ministry of Science and Innovation/National Research Agency (MCIN/AEI) under grants TEC2017- 84378-R, PID2019-109215RB-C41, PID2020-116508RB-I00 and PID2020- 117498RB-I00. Daniel Caudevilla would like to express his thanks for grant PRE2018-083798, provided by the MICINN and the European Social Fund. Francisco Pérez Zenteno would also like to express his thanks for grant 984933, provided by CONACyT (Mexico)., Peer Reviewed, Postprint (author's final draft)

©IEEE. Spanish Conference on Electron Devices (CDE) (13.2021. Sevilla) This work is part of the project TEC2017-84378-R, funded by MICINN and European Social Fund and project MADRID-PV2 (P2018/EMT-4308) funded by the Comunidad Autónoma de Madrid with the support from FEDER Funds. Parts of this research were carried out at IBC at the Helmholtz–Zentrum Dresden–Rossendorf e. V., a member of the Helmholtz Association. Authors would like to thank Ulrich Kentsch for his assistance with the lowtemperature implantations. D. Caudevilla would also acknowledge grant PRE2018-083798, financed by MICINN and European Social Fund. D. Pastor acknowledges financial support from the program Ramón y Cajal (Grant No. RYC2014-16936)., Germanium hyperdoped with deep level donors, such as tellurium, would lead to dopant-mediated sub-band gap mid-infrared photoresponse at room temperature. We use a combination of non-equilibrium techniques to supersaturate Ge with Te via ion implantation followed by pulsed laser melting (PLM). Typically, liquid N2 (77K) temperatures are used to avoid implantation-induced Ge surface porosity. In this work, alternatively, we report on the use of slightly higher implantation temperatures (143 K) together with an amorphous Si (a-Si) capping layer. We demonstrate that the solid solubility limit of Te in Ge is overcome upon recovering the crystallinity of the material after laser processing., Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid/FEDER, Programa Ramón y Cajal, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Este proyecto plantea una mejora de la actividad docente en la asignatura de Fundamentos de Electricidad y Electrónica que se cursa simultáneamente en el primer curso de los grados en Ingeniería Informática, Ingeniería del Software e Ingeniería de Computadores en la facultad de Informática de la Universidad Complutense de Madrid (UCM). Se ha realizado una mejora en la actividad docente mediante métodos de aprendizaje y motivación basados en procesos de clase invertida y otras actividades en clase.

El proyecto ha consistido en la creación de un espacio virtual en Moodle para publicar contenidos complementarios para las asignaturas relacionadas con el área de la Electrónica.

© 2019 Elsevier B.V. All rights reserved. Authors would like to acknowledge the C.A.I. de Técnicas Físicas of the Universidad Complutense de Madrid for ion implantation and evaporation processes. Also, the Institute for Optoelectronics Systems and Microtechnology of the Universidad Politécnica de Madrid for photoluminescence experiments. The fabrication of TEM samples were conducted in the Laboratorio de Microscopias Avanzadas at the Instituto de Nanociencia de Aragón (LMA-INA) of the Universidad de Zaragoza. Authors acknowledge the LMA-INA for offering access to their instruments and expertise, and the Centro Nacional de Microelectrónica at the Moncloa Campus for the TEM and XEDS measurements. This work was partially supported by the Spanish Ministry of Science, Innovation and Universities under grants TEC2017-84378-R and RTI 2018-096498-B-I00. The work of D. Montero was supported by the Spanish MINECO under contract BES-2014-067585. This work is part of the project MADRID-PV2 P-2018/EMT-4308 funded by the Regional Government of Madrid with the support from FEDER funds., We have fabricated GaP supersaturated with Ti by means of ion implantation and pulsed-laser melting to obtain an intermediate band material with applications in photovoltaics. This material has a strong sheet photoconductance at energies below the bandgap of GaP and it seems to be passivated by a Ga defective GaPO oxide layer during the laser process. Passivation is consistently analyzed by sheet photoconductance and photoluminescence measurements. We report on the structural quality of the resulting layers and analyze the energy of the new optical transitions measured on GaP:Ti. A collapse found in the sheet photoconductance spectra of GaP:Ti samples fabricated on undoped substrates is explained by the negative photoconductivity phenomenon. (C) 2019 Elsevier B.V. All rights reserved., Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid/FEDER, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Esta tesis doctoral se enmarca dentro de la tecnología fotovoltaica basada en silicio. El silicio es un material semiconductor con unas propiedades y un desarrollo tecnológico tal que le han convertido en el material más importante de la industria fotovoltaica. En la actualidad, las células solares basadas en silicio suponen el 95 % de toda la potencia fotovoltaica instalada en el mundo. De las células solares basadas en silicio, las que han demostrado tener una mayor eficiencia han sido las células de heterounión. El proceso clave por el cual este tipo de estructuras ostentan dicho récord es por lograr una buena pasivación de la superficie del silicio cristalino..., This thesis is framed in the silicon based photovoltaic technology. Silicon is a semiconductor with properties and a technologic development that make it the most important material in the photovoltaic industry. Currently, silicon-based solar cells are the most extended technology with more than 95% of all photovoltaic power installed in the world. The silicon based solar cells with the highest efficiency are the heterojunction cells. The passivation of the crystalline silicon surface is the key process in these cells...

"Authors would like to acknowledge C.A.I. de Técnicas Físicas of theUniversidad Complutense de Madrid for ion implantation, RTA andJoule and e‐beam evaporations, and the technical and human supportprovided by Facility of Analysis and Characterization of Solids andSurfaces of SAIUEx (financed by UEX, Junta de Extremadura, MICINN,FEDER, and FSE). This work was partially supported by ProjectMADRID‐PV (grant no. P2013/MAE‐2780) funded by the Comunidadde Madrid, by the Spanish MINECO (Ministerio de Economía yCompetitividad) under grants TEC 2013‐41730‐R and TEC 2015‐69916‐C2‐1‐R, and by the Universidad Complutense de Madrid(Programa de Financiación de Grupos de Investigación UCM–BancoSantander) under grant 910173‐2014. The work of D. Montero wassupported by the Spanish MINECO under contract BES‐2014‐067585. J. Solis from the Instituto de Optica is acknowledged for help-ful discussions.", Photovoltaic solar cells based on the intermediate band (IB) concept could greatly enhance theefficiency of future devices. We have analyzed the electrical and photoconductivity propertiesof GaP supersaturated with Ti to assess its suitability for IB solar cells. GaP:Ti was obtained byion implantation followed by pulsed‐laser melting (PLM) using an ArF excimer laser. It was foundthat PLM energy densities between 0.35 and 0.55 J/cm2produced a good recovery of thecrystalline structure of GaP (both unimplanted and implanted with Ti), as evidenced by highmobility measured values (close to the reference GaP). Outside this energy density window,the PLM failed to recover the crystalline structure producing a low mobility layer that iselectrically isolated from the substrate. Spectral photoconductivity measurements wereperformed by using the van der Pauw set up. For GaP:Ti a significant enhancement of theconductivity was observed when illuminating the sample with photon energies below 2.26 eV,suggesting that this photoconductivity is related to the presence of Ti in a concentration highenough to form an IB within the GaP bandgap. The position of the IB was estimated to be around1.1 eV from the conduction band or the valence band of GaP, which would lead to maximumtheoretical efficiencies of 25% to 35% for a selective absorption coefficients scenario and higherfor an overlapping scenario, Comunidad de Madrid, Ministerio de Economía y Competitividad, Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2018 Elsevier B.V. All rights reserved. Authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the use of its laboratories. This work was partially supported by the Project MADRID-PV (Grant No. 2013/MAE-2780) funded by the Comunidad de Madrid, by the Spanish MINECO (Ministerio de Economía y Competitividad) under grants TEC 2013-41730-R, TEC2017-84378-R and ENE2016-78933-C4-1-R. Also by the Universidad Complutense de Madrid (Programa de Financiación de Grupos de Investigación UCM–Banco Santander) under grant 910173-2014. D. Montero acknowledges the Spanish MINECO (Ministerio de Economía y Competitividad) for financial support under contract BES-2014-067585and L.G. Gerling the support from Mexico's grant program CONACyT., Heterojunction solar cells based on molybdenum sub-oxide (MoOx) deposited on n-type crystalline silicon have been fabricated. The hole selective character of MoOx is explained by its high workfunction, which causes a strong band bending in the Si substrate. This bending pushes the surface into inversion. In addition, the sub-stoichiometry of the evaporated MoOx layers leads to a high density of states within the bandgap. This is crucial for charge transport. The J-V electrical characteristics at several temperatures were analysed to elucidate the dominant charge transport mechanisms of this heterojunction structure. We have identified two different transport mechanisms. At low bias voltage, transport is dominated by hole tunnelling through the MoOx gap states. At higher voltage the behaviour is similar to a Schottky junction with a high barrier value, due to the high MoOx work function. These results provide a better understanding of the hole selective character of MoOx/n-type silicon heterocontacts, which is key to further improve this new kind of solar cells., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Universidad Complutense de Madrid/Banco de Santander, Mexico's grant program CONACyT, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© <2018>. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, Heterojunction solar cells based on molybdenum sub-oxide (MoOx) deposited on n-type crystalline silicon have been fabricated. The hole selective character of MoOx is explained by its high workfunction, which causes a strong band bending in the Si substrate. This bending pushes the surface into inversion. In addition, the sub-stoichiometry of the evaporated MoOx layers leads to a high density of states within the bandgap. This is crucial for charge transport. The J-V electrical characteristics at several temperatures were analysed to elucidate the dominant charge transport mechanisms of this heterojunction structure. We have identified two different transport mechanisms. At low bias voltage, transport is dominated by hole tunnelling through the MoOx gap states. At higher voltage the behaviour is similar to a Schottky junction with a high barrier value, due to the high MoOx work function. These results provide a better understanding of the hole selective character of MoOx/n-type silicon heterocontacts, which is key to further improve this new kind of solar cells., Peer Reviewed, Postprint (author's final draft)

© 2017 Elsevier B.V. Authors would like to acknowledge the CAI de Técnicas Físicas of the Universidad Complutense de Madrid for the metallic evaporations and sample etching. This work was partially supported by the Project MADRID-PV (Grant No. P2013/MAE-2780) funded by the Comunidad de Madrid and by the Spanish MINECO (Economic and Competitiviness Ministery) under grant TEC 2013- 41730-R Research by E. García-Hemme was also supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM). D. Pastor acknowledges the financial support to the grant EX-2010-0662 from the Spanish Science Ministry., The van der Pauw method to calculate the sheet resistance and the mobility of a semiconductor is a pervasive technique both in the microelectronics industry and in the condensed matter science field. There are hundreds of papers dealing with the influence of the contact size, nonuniformities and other second order effects. In this paper we will develop a simple methodology to evaluate the error produced by finite size contacts, detect the presence of contact resistance, calculate it for each contact, and determine the linear or rectifying behavior of the contact. We will also calculate the errors produced by the use of voltmeters with finite input resistance in relation with the sample sheet resistance., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Campus de Excelencia Internacional (UCM-UPM), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

The effect of high dose vanadium ion implantation and pulsed laser annealing on the crystal structure and sub-bandgap optical absorption features of V-supersaturated silicon samples has been studied through the combination of experimental and theoretical approaches. Interest in V-supersaturated Si focusses on its potential as a material having a new band within the Si bandgap. Rutherford backscattering spectrometry measurements and formation energies computed through quantum calculations provide evidence that V atoms are mainly located at interstitial positions. The response of sub-bandgap spectral photoconductance is extended far into the infrared region of the spectrum. Theoretical simulations (based on density functional theory and many-body perturbation in GW approximation) bring to light that, in addition to V atoms at interstitial positions, Si defects should also be taken into account in explaining the experimental profile of the spectral photoconductance. The combination of experimental and theoretical methods provides evidence that the improved spectral photoconductance up to 6.2 µm (0.2 eV) is due to new sub-bandgap transitions, for which the new band due to V atoms within the Si bandgap plays an essential role. This enables the use of V-supersaturated silicon in the third generation of photovoltaic devices