Publications (18)22.9 Total impact
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Article: Polarization strategies to improve the emission of Si-based light sources emitting at 1.55μm
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ABSTRACT: We present a electroluminescence (EL) study of the Si-rich silicon oxide (SRSO) LEDs with and without Er3+ ions under different polarization schemes: direct current (DC) and pulsed voltage (PV). The power efficiency of the devices and their main optical limitations are presented. We show that under PV polarization scheme, the devices achieve one order of magnitude superior performance in comparison with DC. Time-resolved measurements have shown that this enhancement is met only for active layers in which annealing temperature is high enough (>1000 °C) for silicon nanocrystal (Si-nc) formation. Modeling of the system with rate equations has been done and excitation cross-sections for both Si-nc and Er3+ ions have been extracted.Highlights► We study the electroluminescence of LPCVD SiOx layers doped or not with Er ions. ► Direct current and pulsed voltage polarization have been used to compare the EL. ► Annealing treatment is correlated with the visible EL improvement in pulsed voltage. ► The improvement is ascribed to the lack of auger processes at the voltage switch off. ► The infrared EL in Er doped devices does not improve under pulsed voltage.Materials Science and Engineering B 12/2012; 177(10):734-738. · 1.52 Impact Factor -
Dataset: O. Jambois J. Phys. D. Appl. Phys. 45 045103 (2012)
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Article: Erbium emission in MOS light emitting devices: from energy transfer to direct impact excitation.
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ABSTRACT: The electroluminescence (EL) at 1.54 μm of metal–oxide–semiconductor (MOS) devices withEr3C ions embedded in the silicon-rich silicon oxide (SRSO) layer has been investigated under different polarization conditions and compared with that of erbium doped SiO2 layers. EL time-resolved measurements allowed us to distinguish between two different excitation mechanisms responsible for the Er3C emission under an alternate pulsed voltage signal (APV). Energy transfer from silicon nanoclusters (Si-ncs) to Er3C is clearly observed at low-field APV excitation. We demonstrate that sequential electron and hole injection at the edges of the pulses creates excited states in Si-ncs which upon recombination transfer their energy to Er3C ions. On the contrary, direct impact excitation of Er3C by hot injected carriers starts at the Fowler–Nordheim injection threshold (above 5 MV cm(-1)) and dominates for high-field APV excitation.Nanotechnology 03/2012; 23(12):125203. · 3.98 Impact Factor -
Article: Modeling of silicon nanocrystals based down-shifter for enhanced silicon solar cell performance
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ABSTRACT: A transfer matrix model of a luminescent down-shifter (LDS) layer, consisting of silicon nanocrystals (Si-NCs) embedded in a silicon oxide matrix, on a silicon solar cells is presented. To enhance the efficiency of the silicon solar cell, we propose using a SiO2/Si-NCs double layer stack, as an anti-reflection-coating (ARC) and as a LDS material. The optical characteristics of this stack have been simulated and optimized as a front surface coating. The cell performances have been simulated by means of a two-dimensional device simulator and compared with the performances of a reference silicon solar cell. We found a 6% relative enhancement of the energy conversion efficiency with respect to the reference cell. We demonstrate that this enhancement results from the lower reflectance and from the down-shifter effect of the Si-NCs activated coating stack.Journal of Applied Physics. 02/2012; 111(3):034303-034303-7. -
Article: Bipolar pulsed excitation of erbium-doped nanosilicon light emitting diodes Bipolar pulsed excitation of erbium-doped nanosilicon light emitting diodes
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ABSTRACT: Identification of device degradation positions in multi-layered phosphorescent organic light emitting devices using water probes Appl. Phys. Lett. 100, 183306 (2012) Efficiency enhancement of blue InGaN/GaN light-emitting diodes with an AlGaN-GaN-AlGaN electron blocking layer J. Appl. Phys. 111, 094503 (2012) Identification of device degradation positions in multi-layered phosphorescent organic light emitting devices using water probes APL: Org. Electron. Photonics 5, 102 (2012) High efficiency warm-white organic light emitting diodes from a single emitter in graded-doping device architecture APL: Org. Electron. Photonics 5, 101 (2012) Additional information on J. Appl. Phys. High quantum efficiency erbium doped silicon nanocluster (Si-NC:Er) light emitting diodes (LEDs) were grown by low-pressure chemical vapor deposition (LPCVD) in a complementary metal-oxide-semiconductor (CMOS) line. Erbium (Er) excitation mechanisms under direct current (DC) and bipolar pulsed electrical injection were studied in a broad range of excitation voltages and frequencies. Under DC excitation, Fowler-Nordheim tunneling of electrons is mediated by Er-related trap states and electroluminescence originates from impact excitation of Er ions. When the bipolar pulsed electrical injection is used, the electron transport and Er excitation mechanism change. Sequential injection of electrons and holes into silicon nanoclusters takes place and nonradiative energy transfer to Er ions is observed. This mechanism occurs in a range of lower driving voltages than those observed in DC and injection frequencies higher than the Er emission rate. V C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694680]Journal of Applied Physics 01/2012; 111(063102). · 2.17 Impact Factor -
Article: Effect of the annealing treatments on the electroluminescence efficiency of SiO2 layers doped with Si and Er
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ABSTRACT: We studied the effect of rapid thermal processing and furnace annealing on the transport properties and electroluminescence (EL) of SiO2 layers doped with Si and Er ions. The results show that for the same annealing temperature, furnace annealing decreases the electrical conductivity and increases the probability of impact excitation, which leads to an improved external quantum efficiency. Correlations between predictions from phenomenological transport models, annealing regimes and erbium EL are observed and discussed.Journal of Physics D-Applied Physics. 01/2012; 45(4). -
Conference Proceeding: 1.54 μm Er doped Light Emitting Devices: Role of Silicon Content
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ABSTRACT: Thin erbium implanted silicon rich oxides films have been used as active layer in light emitting devices. Electroluminescence has been observed and analyzed as a function of the silicon content.The 8th IEEE International Conference on Group IV Photonics 2011, London, England; 09/2011 -
Article: Graded-size Si quantum dot ensembles for efficient light-emitting diodes
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ABSTRACT: We propose a simple way to engineer the energy band gap of an ensemble of silicon nanocrystal (Si-NC) embedded in SiO(2) via thickness/composition profiling of Si-NC multilayers. By means of a complementary metal-oxide-semiconductor compatible process, light emitting diodes (LEDs) which incorporate graded energy gap Si-NC multilayers in the active region have been grown. Electrical and optical properties of these graded Si-NC LEDs demonstrate the ability of the proposed method to tailor the optoelectronic properties of Si-NC devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3658625]Applied Physics Letters 01/2011; 99(18). · 3.84 Impact Factor -
Article: Silicon nanocrystal light emitting device as a bidirectional optical transceiver
Semiconductor Science and Technology. 01/2011; 26(9). -
Article: Power efficiency estimation of silicon nanocrystals based light emitting devices in alternating current regime
Applied Physics Letters 01/2011; 98(20). · 3.84 Impact Factor -
Conference Proceeding: Effect of the annealing treatments on the transport and electroluminescence properties of SiO2 layers doped with Er and Si nanoclusters
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ABSTRACT: We studied the effect of RTP and furnace annealing on the transport properties and electroluminescence of Si-nc embedded in SiO2 layers, and of Er ions coupled to Si-nc. The light emitting devices have been fabricated in a CMOS line by implantation of Si and Er in SiO2. The results show that for the same annealing temperature, furnace annealing decreases electrical conductivity and increases probability of impact excitation, which leads to an improved external quantum efficiency. Correlations between phenomenological transport models, annealing regimes, and erbium electroluminescence are observed and discussed.MRS proceeding, Boston, USA; 11/2010 -
Conference Proceeding: Photovoltaic properties of Si nanostructure based solar cells fabricated on quartz
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ABSTRACT: Solar cells with different silicon nanostructures have been fabricated on quartz wafers. A correlation between their photovoltaic properties and the conductivity was clearly found. The best results are achieved for amorphous silicon based nanostructures.Group IV Photonics (GFP), 2010 7th IEEE International Conference on; 10/2010 -
Article: Low-voltage onset of electroluminescence in nanocrystalline-Si/SiO2 multilayers
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ABSTRACT: Thin film metal-oxide-semiconductor light emitting devices (LEDs) based on nanocrystalline silicon multilayer structure were grown by plasma-enhanced chemical vapor deposition. Room temperature electroluminescence was studied under direct current and time-resolved pulsed-current injection schemes. Multilayer LEDs operating at voltages below 5 V and electroluminescence turn-on voltage of 1.4–1.7 V are demonstrated. The turn-on voltage is less than 3.2 V which corresponds to the barrier height at the silicon oxide interface for electrons. Electrical injection in the multilayer LED is controlled by direct tunneling of electrons and holes among silicon nanocrystals. This injection regime is different than the Fowler–Nordheim tunneling that controls the electron injection in single thick layer LED operating at high voltages. A comparison of the power efficiency for the multilayer based LED and a similar single thick layer LED shows larger power efficiency for the former than for the second. Our results open new directions in the development of highly efficient room temperature silicon based LED.Journal of Applied Physics 09/2009; · 2.17 Impact Factor -
Article: Low-voltage onset of electroluminescence in nanocrystalline-Si/SiO(2) multilayers
Journal of Applied Physics. 01/2009; 106(3). -
Article: Light emitting devices based on nanocrystalline-silicon multilayer structure
Physica E Low-dimensional Systems and Nanostructures 01/2009; 41(6):912-915. · 1.53 Impact Factor -
Article: High power efficiency in Si-nc/SiO(2) multilayer light emitting devices by bipolar direct tunneling
Applied Physics Letters 01/2009; 94(22). · 3.84 Impact Factor -
Conference Proceeding: Electroluminescence from nanocrystalline-Si/SiO2 multilayers with an electron injection barrier
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ABSTRACT: The effect of an injection barrier placed on top of a nanocrystalline-Si/SiO<sub>2</sub> multilayered LED is discussed. Direct and alternating current injection schemes and time resolved electroluminescence are reported.Group IV Photonics, 2008 5th IEEE International Conference on; 10/2008 -
Conference Proceeding: Photovoltaic effect in ultra-thin a-Si/SiO2 multilayered structures
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ABSTRACT: Photovoltaic and photoconductive properties of ultra-thin a-Si/SiO<sub>2</sub> multilayers grown by PECVD and annealed at 1150degC were studied. A quantum yield greater than one is observed due to secondary carrier generation from interface trap states.Group IV Photonics, 2008 5th IEEE International Conference on; 10/2008
Top co-authors
Top Journals
Institutions
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2012
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University of Barcelona
- Departament d'Electrònica
Barcelona, Catalonia, Spain
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2008–2012
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Università degli Studi di Trento
- Department of Physics
Trento, Trentino-Alto Adige, Italy
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