Search

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 cm−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.

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

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

© 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)

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

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)

© 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

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.