In this work, for the first time, we intentionally deposit an ultrathin layer of excess methyl am... more In this work, for the first time, we intentionally deposit an ultrathin layer of excess methyl ammonium iodide (MAI) on top of a methyl ammonium lead iodide (MAPI) perovskite film. Using photoelectron spectroscopy, we investigate the role of excess MAI at the interface between perovskite and spiro-MeOTAD hole transport layer in standard structure perovskite solar cells (PSCs). We found that interfacial, favorable, energy-level tuning of the MAPI film can be achieved by controlling the amount of excess MAI on top of the MAPI film. Our XPS results reveal that MAI dissociates at low thicknesses (< 16 nm) when deposited on MAPbI 3. It is not the MAI layer, but the dissociated species that leads to the interfacial energy-level tuning. Optimized interface energetics were verified by solar cell device testing, leading to both an increase of 19% in average steady state power conversion efficiency (PCE) and significantly improved reproducibility, which is represented by a much lower PCE standard deviation (from 15 ± 2% and 17.2 ± 0.4%).
Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photode... more Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photodetection due to its controllable heterojunction bandgap and sensitivity to normal incident radiation. It is expected to be superior to infrared photodetectors of mature technologies such as Mercury Cadmium Telluride (HgCdTe) or a quantum well infrared photodetector. In the presented paper, we have developed a theoretical model for the dark current in truncated conical QDIP as the truncated conical shaped QD structure is more appropriate to describe the fabricated dots. The dark current model is based on the drift diffusion model solving the main governing Poisson's and continuity equations. In this model, the carrier mobility is calculated by solving time-dependent Boltzmann transport equation in the photodetector material with embedded truncated conical QDs using finite difference technique. The results of the developed model have been compared with the dark current characteristics with published experimental results of Indium Arsenide/Gallium Arsenide (InAs/GaAs) truncated QDIP. The effects of QD volume, QD aspect ratio and QD density and the operating temperature on the dark current characteristics have also been investigated.
Due to the fabrication processes, inaccurate manufacturing of the photonic crystals (PCs) might o... more Due to the fabrication processes, inaccurate manufacturing of the photonic crystals (PCs) might occur which affect their performance. In this paper, we examine the effects of tolerance variations of the radii of the rods and the permittivity of the material of the two-dimensional PCs on their performance. The presented stochastic analysis relies on plane wave expansion method and Mote Carlo simulations. We focus on two structures, namely Si-Rods PCs and Air-Holes PCs. Numerical results showfor both structuresthat uncertainties in the dimensions of the PCs have higher impact on its photonic gap than do the uncertainties in the permittivity of the Si material. In addition, Air-Holes PCs could be a good candidate with least alteration in the photonic gap considering deviations that might occur in the permittivity of Si due to impurities up to 5%.
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
In this paper a novel nanoparticle structure has been presented to be used in plasmonic photovolt... more In this paper a novel nanoparticle structure has been presented to be used in plasmonic photovoltaic to enhance its efficiency. The proposed structure enhances the light absorption inside the active layer of the photovoltaics (PV) in the visible and near infrared range of frequencies (200–900 THz). In this work, the proposed nano-antenna, nantenna, takes the shape of crescent with a gap on its narrow side. This nantenna is embedded inside the photovoltaic cell resulting in a highly confined near-field around the nanoparticle and within the semiconductor forming the PV. The extinction cross-section of the proposed nanoparticle in vacuum has been calculated versus wavelength. Also, the modal fields are studied. The effect of embedding this crescent nanoparticle in a silicon photovoltaic is investigated by comparing its absorption with the conventional disk nanoparticle. The proposed structure enhances the light absorption leading to improvement of the efficiency of the PV cells.
In Resonant Cavity Enhanced Photodetectors (RCE-PDs), the trade-off between the bandwidth and the... more In Resonant Cavity Enhanced Photodetectors (RCE-PDs), the trade-off between the bandwidth and the quantum efficiency in the conventional photodetectors is overcome. In RCE-PDs, large bandwidth can be achieved using a thin absorption layer while the use of a resonant cavity allows for multiple passes of light in the absorption which boosts the quantum efficiency. In this paper, a complete bias-dependent model for the Resonant Cavity Enhanced-Separated Absorption Graded Charge Multiplication-Avalanche Photodetector (RCE-SAGCM-APD) is presented. The proposed model takes into account the case of drift velocities other than the saturation velocity, thus modeling this effect on the photodetector different design parameters such as Gain, Bandwidth and Gain-Bandwidth product.
Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photode... more Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photodetection due to its controllable heterojunction bandgap and sensitivity to normal incident radiation. It is expected to be superior to infrared photodetectors of mature technologies such as an HgCdTe or a quantum well infrared photodetector. In the presented paper, we have developed a theoretical model for the dark current in truncated conical QDIP as the truncated conical shaped QD structure is more appropriate to describe the fabricated dots. The dark current model is based on the drift diffusion model solving the main governing Poisson’s and continuity equations. In this model, the carrier mobility is calculated by solving time-dependent Boltzmann transport equation in the photodetector material with embedded truncated conical QDs using finite difference technique. The results of the developed model have been compared with the dark current characteristics with published experimental re...
Light trapping as a result of embedding plasmonic Nano-Particles (NPs) into Photovoltaics (PVs) h... more Light trapping as a result of embedding plasmonic Nano-Particles (NPs) into Photovoltaics (PVs) has been recently used to achieve better optical performance compared to conventional PVs. This light trapping technique enhances the efficiency of PVs by confining the incident light into hot-spot field regions around the NPs, which possess higher absorption, thus more enhancing of photocurrent. This research aims to study the impact of embedding metallic pyramidal-shaped NPs inside the PV’s active region for enhancing the efficiency of plasmonic silicon PVs. The optical properties of the pyramidal-shaped NPs in the visible and near-infrared spectrum have been investigated.The light absorption into silicon PV is significantly enhanced by embedding periodic arrays of pyramidal NPs in the cell comparedto the case of bare silicon PV. Furthermore, the effects of varying the pyramidal-shaped NPs dimensions on the absorption enhancement are studied. In addition, a sensitivity analysis has been...
This paper develops and evaluates a new topology of a planar metamaterial terahertz sensor. The s... more This paper develops and evaluates a new topology of a planar metamaterial terahertz sensor. The sensor is constructed by overlapping two E-shaped gold patches placed on top of a grounded dielectric substrate. The absorption spectrum includes peak resonances as a result of the electric field being contained within the gaps between the metallic arms. Two geometrical configurations of the proposed structure are presented and compared. The first configuration realizes a perfect overlap between the horizontal arms of the two E-patches. Almost absorption of (98%) occurs at 5.74 THz with an average sensitivity of 2.8 THz/RIU and a quality factor of 11.39, when the analyte refractive index is varied in the range between n = 1 to n = 1.4. The overlapping distance between the metallic arms is minimized for the second configuration. Therefore, the electric field is more localized within the small gap created between the overlapped arms of the two E-patches. The absorption, sensitivity, and qua...
Coupled Line Microstrip Bandpass Filters are considered as a promising candidate for bandpass fil... more Coupled Line Microstrip Bandpass Filters are considered as a promising candidate for bandpass filter for wireless and high frequency applications because of their small size, low cost and easy engineered fabrication. In this paper, a stochastic analysis of this coupled line bandpass filter which is based on Monte Carlo Model is developed, where the tolerances in the design parameters of this microstrip bandpass filter and their impacts on the filter performance are investigated. These design parameters include the thickness of the strips of the bandpass filter, their lengths and the spacing between them. The mean, the standard deviations and the probability distribution function of both the central frequency and the operating bandwidth are studied.
2020 2nd Novel Intelligent and Leading Emerging Sciences Conference (NILES), 2020
Concentrated Solar Power (CSP) systems have a good potential as a renewable energy candidate that... more Concentrated Solar Power (CSP) systems have a good potential as a renewable energy candidate that are based on converting the incident solar thermal energy to an electrical energy. In this paper, CSP using spot Fresnel lens instead of traditional lenses is presented to enhance the efficiency of the system, where Silicon Carbide (SiC) is used as a coating material for the receiver of the system due to its high thermal conductivity. The presented prototype has been investigated for uncoated spot Fresnel lens CSP, and for spot Fresnel lens CSP with the SiC as a coating material showing the enhancement of the presented design. The experimental efficiency of this design shows a significant improvement in the CSP efficiency.
2017 IEEE International Conference on Telecommunications and Photonics (ICTP), 2017
Single photon avalanche detector is widely used for the optical detection of weak signals utilizi... more Single photon avalanche detector is widely used for the optical detection of weak signals utilizing photocurrent multiplication mechanism beyond the breakdown voltage. In the present work, photocurrent characteristics of InGaAs/InP based SPAD device are analysed. The device in the model employs self-differencing method and operates in gated mode with 1GHz gating frequency in near infrared region. Dark count probabilities have been generated for varying single photon detection efficiency (SPDE). The results of current-voltage characteristics (for operating temperatures −50, −30, 0 and 20 degree Celsius) and dark count probability as a function of SPDE have been examined by comparing them with published experimental results. Error analysis shows that the deviation of the present model from the experimental results is low in room temperature and agrees with the experimental values within 3% range.
For the first time, we intentionally deposit an ultrathin layer of excess methylammonium iodide (... more For the first time, we intentionally deposit an ultrathin layer of excess methylammonium iodide (MAI) on top of a methylammonium lead iodide (MAPI) perovskite film. Using photoelectron spectroscopy, we investigate the role of excess MAI at the interface between perovskite and spiro-MeOTAD hole-transport layer in standard structure perovskite solar cells (PSCs). We found that interfacial, favorable, energy-level tuning of the MAPI film can be achieved by controlling the amount of excess MAI on top of the MAPI film. Our XPS results reveal that MAI dissociates at low thicknesses (<16 nm) when deposited on MAPbI 3. It is not the MAI layer but the dissociated species that leads to the interfacial energy-level tuning. Optimized interface energetics were verified by solar cell device testing, leading to both an increase of 19% in average steady-state power conversion efficiency (PCE) and significantly improved reproducibility, which is represented by a much lower PCE standard deviation (from 15 ± 2% to 17.2 ± 0.4%).
Resonant cavity enhanced photodetectors (RCE-PDs) are promising candidates for applications in hi... more Resonant cavity enhanced photodetectors (RCE-PDs) are promising candidates for applications in high-speed optical communications and interconnections. In these high-speed photodetectors, both high bandwidth and high external quantum efficiency can be achieved simultaneously because of the multipaths of the incident light due to the presence of the Fabry- Pérot cavity into which the photodetector is inserted. In this paper, state-of-the-art RCE-PDs
Self assembled quantum dots have shown a great promise as a leading candidate for infrared detect... more Self assembled quantum dots have shown a great promise as a leading candidate for infrared detection at room temperature. In this paper, a theoretical model of the absorption coefficient of quantum dot devices is presented. Both of bound to bound absorption and bound to continuum absorption are taken into consideration in this model. This model is based on the effective mass theory and the Non Equilibrium Greens Function (NEGF) formalism. NEGF formalism is used to calculate the bound to continuum absorption coefficient. The results of the model have been compared with a published experimental work and a good agreement is obtained. Based on the presented model, the bound to bound absorption coefficient component is compared to the bound to continuum absorption coefficient component. In addition, the effects of the dot dimensions and electron filling on the bound to continuum absorption coefficient are also investigated. In general, increasing the dot filling increases the absorption and decreasing the dots dimensions will increase the absorption and move the absorption peak towards longer wavelengths.
International Symposium on Photonics and Optoelectronics 2014, 2014
ABSTRACT Waveguide photodetectors (WGPDs) are considered a leading candidate to overcome the band... more ABSTRACT Waveguide photodetectors (WGPDs) are considered a leading candidate to overcome the bandwidth-quantum efficiency trade-off as the flow of the photon and carrier fluxes are perpendicular to each other enabling high date rate applications. Mushroom-WGPD was proposed to overcome the trade-off between the capacitance of the photodetector and the contact resistance. In this paper, an extended calibrated circuit model for mushroom-WGPD, including the effect of the biasing of the photodetector, is presented so resulting in the feasibility of a complete circuit simulation of the entire photoreceiver circuit. The effects of the biasing over the performance of Mushroom-WGPDs have been explored for different loads and different dimensions of the device. Based on the studies of different parameters for design and materials, optimization has been performed for the mushroom-WGPD. With this optimization, the optimal values of the thickness of the absorption layer to produce the highest bandwidth of the photodetector are obtained for different biasing values. These optimizations are performed for different areas of the photodetector and also for different load resistors, and they result in a significant improvement in the performance of the mushroom-WGPDs.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2004
Waveguide photodetectors ͑WGPDs͒ are promising candidates for applications in high-speed optical ... more Waveguide photodetectors ͑WGPDs͒ are promising candidates for applications in high-speed optical communications and interconnections. In these high-speed photodetectors, both high bandwidth and high external quantum efficiency can be achieved simultaneously. Mushroom-WGPD is proposed to overcome the trade-off between the capacitance and contact resistance of the photodetector. In this article, a physical model of the mushroom-WGPD is presented including both time and frequency responses of this photodetector and how they depend on the parameters of the photodetector. A SPICE model for mushroom-WGPD including all the parasitics is also presented, showing the dependence of the transfer function of this model on the dimensions and the material parameters of the photodetector. The effects of the parasitics are also studied for different photodetector areas. The characteristics of mushroom-WGPD are studied for two cases, first without an inductor added in series with the load resistance and second, if an inductor is added in series to the load resistor. A significant improvement in performance is achieved in the second case where an inductor is added.
We present a detailed analysis, optimization, and SPICE modeling of the resonant-cavity-enhanced ... more We present a detailed analysis, optimization, and SPICE modeling of the resonant-cavity-enhanced p-in photodetector (RCE-p-in -PD). Time response, frequency response, and the quality factor of RCE-p-in -PD are calculated for different thicknesses of the active layer and for different areas of the photodetector. The standing-wave effect is examined for all these calculations. The effect of the parasitic inductor is studied, and then an optimization is applied to the photodetector to get the optimal value of thickness of the active layer and the series inductor values. Two cases are compared, one with an inductor () in series with the load resistor (), and another without this inductor. High performance is obtained in the first case with an inductor, and its optimal values are obtained. A SPICE model for this high-speed photodetector is also presented, and the transfer function of this model is compared for different parameters of the device. Finally, predictions from this SPICE model are compared with published experimental results. Index Terms-Modeling, optimization, photodetector SPICE modeling, photodetectors, photodiode frequency response, photodiode parasitic effects, photodiode time response, photodiodes, p-in photodiodes, resonant-cavity-enhanced (RCE) photodiodes, resonant-cavity-enhanced (RCE) p-in photodiode, resonant-cavity-enhanced photodetectors (RCE-PD), standing-wave effect. NOMENCLATURE Area of the photodetector. Total capacitance of the photodetector. Thickness of the active region. Distributed Bragg reflector. 3-dB bandwidth of the photodetector. Planck's constant. Transfer function of the SPICE model of RCE-p-in -PD. Photogenerated current of the photodetector. Optical incident current. Parasitic inductance of the photodetector including the wire bond inductance. , Thickness of the n-layer and the player , respectively. , Total photogenerated electrons resulted from forward and reflected wave, respectively. , Total photogenerated electrons and holes, respectively.
ABSTRACT A theoretical model of the absorption coefficient of quantum dot devices is presented. B... more ABSTRACT A theoretical model of the absorption coefficient of quantum dot devices is presented. Both of bound to bound absorption and bound to continuum absorption are taken into consideration in this model which is based on the effective mass theory and the nonequilibrium Greens function formalism. The results of the model have been compared with a published experimental work and a good agreement is obtained. The effects of the dot dimensions and electron filling on the bound to continuum absorption coefficient are also investigated. In general, increasing the dot filling increases the absorption and decreasing the dots dimensions will increase the absorption and move the absorption peak towards longer wavelengths.
In this work, for the first time, we intentionally deposit an ultrathin layer of excess methyl am... more In this work, for the first time, we intentionally deposit an ultrathin layer of excess methyl ammonium iodide (MAI) on top of a methyl ammonium lead iodide (MAPI) perovskite film. Using photoelectron spectroscopy, we investigate the role of excess MAI at the interface between perovskite and spiro-MeOTAD hole transport layer in standard structure perovskite solar cells (PSCs). We found that interfacial, favorable, energy-level tuning of the MAPI film can be achieved by controlling the amount of excess MAI on top of the MAPI film. Our XPS results reveal that MAI dissociates at low thicknesses (< 16 nm) when deposited on MAPbI 3. It is not the MAI layer, but the dissociated species that leads to the interfacial energy-level tuning. Optimized interface energetics were verified by solar cell device testing, leading to both an increase of 19% in average steady state power conversion efficiency (PCE) and significantly improved reproducibility, which is represented by a much lower PCE standard deviation (from 15 ± 2% and 17.2 ± 0.4%).
Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photode... more Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photodetection due to its controllable heterojunction bandgap and sensitivity to normal incident radiation. It is expected to be superior to infrared photodetectors of mature technologies such as Mercury Cadmium Telluride (HgCdTe) or a quantum well infrared photodetector. In the presented paper, we have developed a theoretical model for the dark current in truncated conical QDIP as the truncated conical shaped QD structure is more appropriate to describe the fabricated dots. The dark current model is based on the drift diffusion model solving the main governing Poisson's and continuity equations. In this model, the carrier mobility is calculated by solving time-dependent Boltzmann transport equation in the photodetector material with embedded truncated conical QDs using finite difference technique. The results of the developed model have been compared with the dark current characteristics with published experimental results of Indium Arsenide/Gallium Arsenide (InAs/GaAs) truncated QDIP. The effects of QD volume, QD aspect ratio and QD density and the operating temperature on the dark current characteristics have also been investigated.
Due to the fabrication processes, inaccurate manufacturing of the photonic crystals (PCs) might o... more Due to the fabrication processes, inaccurate manufacturing of the photonic crystals (PCs) might occur which affect their performance. In this paper, we examine the effects of tolerance variations of the radii of the rods and the permittivity of the material of the two-dimensional PCs on their performance. The presented stochastic analysis relies on plane wave expansion method and Mote Carlo simulations. We focus on two structures, namely Si-Rods PCs and Air-Holes PCs. Numerical results showfor both structuresthat uncertainties in the dimensions of the PCs have higher impact on its photonic gap than do the uncertainties in the permittivity of the Si material. In addition, Air-Holes PCs could be a good candidate with least alteration in the photonic gap considering deviations that might occur in the permittivity of Si due to impurities up to 5%.
2017 11th European Conference on Antennas and Propagation (EUCAP), 2017
In this paper a novel nanoparticle structure has been presented to be used in plasmonic photovolt... more In this paper a novel nanoparticle structure has been presented to be used in plasmonic photovoltaic to enhance its efficiency. The proposed structure enhances the light absorption inside the active layer of the photovoltaics (PV) in the visible and near infrared range of frequencies (200–900 THz). In this work, the proposed nano-antenna, nantenna, takes the shape of crescent with a gap on its narrow side. This nantenna is embedded inside the photovoltaic cell resulting in a highly confined near-field around the nanoparticle and within the semiconductor forming the PV. The extinction cross-section of the proposed nanoparticle in vacuum has been calculated versus wavelength. Also, the modal fields are studied. The effect of embedding this crescent nanoparticle in a silicon photovoltaic is investigated by comparing its absorption with the conventional disk nanoparticle. The proposed structure enhances the light absorption leading to improvement of the efficiency of the PV cells.
In Resonant Cavity Enhanced Photodetectors (RCE-PDs), the trade-off between the bandwidth and the... more In Resonant Cavity Enhanced Photodetectors (RCE-PDs), the trade-off between the bandwidth and the quantum efficiency in the conventional photodetectors is overcome. In RCE-PDs, large bandwidth can be achieved using a thin absorption layer while the use of a resonant cavity allows for multiple passes of light in the absorption which boosts the quantum efficiency. In this paper, a complete bias-dependent model for the Resonant Cavity Enhanced-Separated Absorption Graded Charge Multiplication-Avalanche Photodetector (RCE-SAGCM-APD) is presented. The proposed model takes into account the case of drift velocities other than the saturation velocity, thus modeling this effect on the photodetector different design parameters such as Gain, Bandwidth and Gain-Bandwidth product.
Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photode... more Quantum Dot Infrared Photodetector (QDIP) is one of the promising candidates for infrared photodetection due to its controllable heterojunction bandgap and sensitivity to normal incident radiation. It is expected to be superior to infrared photodetectors of mature technologies such as an HgCdTe or a quantum well infrared photodetector. In the presented paper, we have developed a theoretical model for the dark current in truncated conical QDIP as the truncated conical shaped QD structure is more appropriate to describe the fabricated dots. The dark current model is based on the drift diffusion model solving the main governing Poisson’s and continuity equations. In this model, the carrier mobility is calculated by solving time-dependent Boltzmann transport equation in the photodetector material with embedded truncated conical QDs using finite difference technique. The results of the developed model have been compared with the dark current characteristics with published experimental re...
Light trapping as a result of embedding plasmonic Nano-Particles (NPs) into Photovoltaics (PVs) h... more Light trapping as a result of embedding plasmonic Nano-Particles (NPs) into Photovoltaics (PVs) has been recently used to achieve better optical performance compared to conventional PVs. This light trapping technique enhances the efficiency of PVs by confining the incident light into hot-spot field regions around the NPs, which possess higher absorption, thus more enhancing of photocurrent. This research aims to study the impact of embedding metallic pyramidal-shaped NPs inside the PV’s active region for enhancing the efficiency of plasmonic silicon PVs. The optical properties of the pyramidal-shaped NPs in the visible and near-infrared spectrum have been investigated.The light absorption into silicon PV is significantly enhanced by embedding periodic arrays of pyramidal NPs in the cell comparedto the case of bare silicon PV. Furthermore, the effects of varying the pyramidal-shaped NPs dimensions on the absorption enhancement are studied. In addition, a sensitivity analysis has been...
This paper develops and evaluates a new topology of a planar metamaterial terahertz sensor. The s... more This paper develops and evaluates a new topology of a planar metamaterial terahertz sensor. The sensor is constructed by overlapping two E-shaped gold patches placed on top of a grounded dielectric substrate. The absorption spectrum includes peak resonances as a result of the electric field being contained within the gaps between the metallic arms. Two geometrical configurations of the proposed structure are presented and compared. The first configuration realizes a perfect overlap between the horizontal arms of the two E-patches. Almost absorption of (98%) occurs at 5.74 THz with an average sensitivity of 2.8 THz/RIU and a quality factor of 11.39, when the analyte refractive index is varied in the range between n = 1 to n = 1.4. The overlapping distance between the metallic arms is minimized for the second configuration. Therefore, the electric field is more localized within the small gap created between the overlapped arms of the two E-patches. The absorption, sensitivity, and qua...
Coupled Line Microstrip Bandpass Filters are considered as a promising candidate for bandpass fil... more Coupled Line Microstrip Bandpass Filters are considered as a promising candidate for bandpass filter for wireless and high frequency applications because of their small size, low cost and easy engineered fabrication. In this paper, a stochastic analysis of this coupled line bandpass filter which is based on Monte Carlo Model is developed, where the tolerances in the design parameters of this microstrip bandpass filter and their impacts on the filter performance are investigated. These design parameters include the thickness of the strips of the bandpass filter, their lengths and the spacing between them. The mean, the standard deviations and the probability distribution function of both the central frequency and the operating bandwidth are studied.
2020 2nd Novel Intelligent and Leading Emerging Sciences Conference (NILES), 2020
Concentrated Solar Power (CSP) systems have a good potential as a renewable energy candidate that... more Concentrated Solar Power (CSP) systems have a good potential as a renewable energy candidate that are based on converting the incident solar thermal energy to an electrical energy. In this paper, CSP using spot Fresnel lens instead of traditional lenses is presented to enhance the efficiency of the system, where Silicon Carbide (SiC) is used as a coating material for the receiver of the system due to its high thermal conductivity. The presented prototype has been investigated for uncoated spot Fresnel lens CSP, and for spot Fresnel lens CSP with the SiC as a coating material showing the enhancement of the presented design. The experimental efficiency of this design shows a significant improvement in the CSP efficiency.
2017 IEEE International Conference on Telecommunications and Photonics (ICTP), 2017
Single photon avalanche detector is widely used for the optical detection of weak signals utilizi... more Single photon avalanche detector is widely used for the optical detection of weak signals utilizing photocurrent multiplication mechanism beyond the breakdown voltage. In the present work, photocurrent characteristics of InGaAs/InP based SPAD device are analysed. The device in the model employs self-differencing method and operates in gated mode with 1GHz gating frequency in near infrared region. Dark count probabilities have been generated for varying single photon detection efficiency (SPDE). The results of current-voltage characteristics (for operating temperatures −50, −30, 0 and 20 degree Celsius) and dark count probability as a function of SPDE have been examined by comparing them with published experimental results. Error analysis shows that the deviation of the present model from the experimental results is low in room temperature and agrees with the experimental values within 3% range.
For the first time, we intentionally deposit an ultrathin layer of excess methylammonium iodide (... more For the first time, we intentionally deposit an ultrathin layer of excess methylammonium iodide (MAI) on top of a methylammonium lead iodide (MAPI) perovskite film. Using photoelectron spectroscopy, we investigate the role of excess MAI at the interface between perovskite and spiro-MeOTAD hole-transport layer in standard structure perovskite solar cells (PSCs). We found that interfacial, favorable, energy-level tuning of the MAPI film can be achieved by controlling the amount of excess MAI on top of the MAPI film. Our XPS results reveal that MAI dissociates at low thicknesses (<16 nm) when deposited on MAPbI 3. It is not the MAI layer but the dissociated species that leads to the interfacial energy-level tuning. Optimized interface energetics were verified by solar cell device testing, leading to both an increase of 19% in average steady-state power conversion efficiency (PCE) and significantly improved reproducibility, which is represented by a much lower PCE standard deviation (from 15 ± 2% to 17.2 ± 0.4%).
Resonant cavity enhanced photodetectors (RCE-PDs) are promising candidates for applications in hi... more Resonant cavity enhanced photodetectors (RCE-PDs) are promising candidates for applications in high-speed optical communications and interconnections. In these high-speed photodetectors, both high bandwidth and high external quantum efficiency can be achieved simultaneously because of the multipaths of the incident light due to the presence of the Fabry- Pérot cavity into which the photodetector is inserted. In this paper, state-of-the-art RCE-PDs
Self assembled quantum dots have shown a great promise as a leading candidate for infrared detect... more Self assembled quantum dots have shown a great promise as a leading candidate for infrared detection at room temperature. In this paper, a theoretical model of the absorption coefficient of quantum dot devices is presented. Both of bound to bound absorption and bound to continuum absorption are taken into consideration in this model. This model is based on the effective mass theory and the Non Equilibrium Greens Function (NEGF) formalism. NEGF formalism is used to calculate the bound to continuum absorption coefficient. The results of the model have been compared with a published experimental work and a good agreement is obtained. Based on the presented model, the bound to bound absorption coefficient component is compared to the bound to continuum absorption coefficient component. In addition, the effects of the dot dimensions and electron filling on the bound to continuum absorption coefficient are also investigated. In general, increasing the dot filling increases the absorption and decreasing the dots dimensions will increase the absorption and move the absorption peak towards longer wavelengths.
International Symposium on Photonics and Optoelectronics 2014, 2014
ABSTRACT Waveguide photodetectors (WGPDs) are considered a leading candidate to overcome the band... more ABSTRACT Waveguide photodetectors (WGPDs) are considered a leading candidate to overcome the bandwidth-quantum efficiency trade-off as the flow of the photon and carrier fluxes are perpendicular to each other enabling high date rate applications. Mushroom-WGPD was proposed to overcome the trade-off between the capacitance of the photodetector and the contact resistance. In this paper, an extended calibrated circuit model for mushroom-WGPD, including the effect of the biasing of the photodetector, is presented so resulting in the feasibility of a complete circuit simulation of the entire photoreceiver circuit. The effects of the biasing over the performance of Mushroom-WGPDs have been explored for different loads and different dimensions of the device. Based on the studies of different parameters for design and materials, optimization has been performed for the mushroom-WGPD. With this optimization, the optimal values of the thickness of the absorption layer to produce the highest bandwidth of the photodetector are obtained for different biasing values. These optimizations are performed for different areas of the photodetector and also for different load resistors, and they result in a significant improvement in the performance of the mushroom-WGPDs.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2004
Waveguide photodetectors ͑WGPDs͒ are promising candidates for applications in high-speed optical ... more Waveguide photodetectors ͑WGPDs͒ are promising candidates for applications in high-speed optical communications and interconnections. In these high-speed photodetectors, both high bandwidth and high external quantum efficiency can be achieved simultaneously. Mushroom-WGPD is proposed to overcome the trade-off between the capacitance and contact resistance of the photodetector. In this article, a physical model of the mushroom-WGPD is presented including both time and frequency responses of this photodetector and how they depend on the parameters of the photodetector. A SPICE model for mushroom-WGPD including all the parasitics is also presented, showing the dependence of the transfer function of this model on the dimensions and the material parameters of the photodetector. The effects of the parasitics are also studied for different photodetector areas. The characteristics of mushroom-WGPD are studied for two cases, first without an inductor added in series with the load resistance and second, if an inductor is added in series to the load resistor. A significant improvement in performance is achieved in the second case where an inductor is added.
We present a detailed analysis, optimization, and SPICE modeling of the resonant-cavity-enhanced ... more We present a detailed analysis, optimization, and SPICE modeling of the resonant-cavity-enhanced p-in photodetector (RCE-p-in -PD). Time response, frequency response, and the quality factor of RCE-p-in -PD are calculated for different thicknesses of the active layer and for different areas of the photodetector. The standing-wave effect is examined for all these calculations. The effect of the parasitic inductor is studied, and then an optimization is applied to the photodetector to get the optimal value of thickness of the active layer and the series inductor values. Two cases are compared, one with an inductor () in series with the load resistor (), and another without this inductor. High performance is obtained in the first case with an inductor, and its optimal values are obtained. A SPICE model for this high-speed photodetector is also presented, and the transfer function of this model is compared for different parameters of the device. Finally, predictions from this SPICE model are compared with published experimental results. Index Terms-Modeling, optimization, photodetector SPICE modeling, photodetectors, photodiode frequency response, photodiode parasitic effects, photodiode time response, photodiodes, p-in photodiodes, resonant-cavity-enhanced (RCE) photodiodes, resonant-cavity-enhanced (RCE) p-in photodiode, resonant-cavity-enhanced photodetectors (RCE-PD), standing-wave effect. NOMENCLATURE Area of the photodetector. Total capacitance of the photodetector. Thickness of the active region. Distributed Bragg reflector. 3-dB bandwidth of the photodetector. Planck's constant. Transfer function of the SPICE model of RCE-p-in -PD. Photogenerated current of the photodetector. Optical incident current. Parasitic inductance of the photodetector including the wire bond inductance. , Thickness of the n-layer and the player , respectively. , Total photogenerated electrons resulted from forward and reflected wave, respectively. , Total photogenerated electrons and holes, respectively.
ABSTRACT A theoretical model of the absorption coefficient of quantum dot devices is presented. B... more ABSTRACT A theoretical model of the absorption coefficient of quantum dot devices is presented. Both of bound to bound absorption and bound to continuum absorption are taken into consideration in this model which is based on the effective mass theory and the nonequilibrium Greens function formalism. The results of the model have been compared with a published experimental work and a good agreement is obtained. The effects of the dot dimensions and electron filling on the bound to continuum absorption coefficient are also investigated. In general, increasing the dot filling increases the absorption and decreasing the dots dimensions will increase the absorption and move the absorption peak towards longer wavelengths.
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Papers by Yasser El-Batawy