Sfina Noureddine - Academia.edu (original) (raw)
Papers by Sfina Noureddine
The European Physical Journal B, 2005
In view of the fact that the bandwidth required in optical fiber communication systems will excee... more In view of the fact that the bandwidth required in optical fiber communication systems will exceed 100 Gb s −1 , ultrafast optical switching and modulation devices with high efficiency must be developed. Given that intersubband transitions (ISBT) in quantum wells (QWs) are one of the important ultrafast phenomena, a numerical study of intersubband transition (ISBT) properties in (CdS/ZnSe)/BeTe QWs is considered. The structure modeled consists of a few monolayers of CdS embedded in a ZnSe/BeTe QW. A self-consistent analysis is made to achieve the desired properties and device applications. Variation of CdS well thickness leads to tailoring of the band alignment, achieving optical transitions in the wavelength range of 1.33-1.55 µm wavelengths for applications in optical fiber transmission. To analyze the optical behavior of the heterostructure under investigation, we have calculated the CdS well thickness-dependant oscillator strengths and electron emission energy of the intersubband transition between the two first states in the well. An attempt to explain our results will be presented.
physica status solidi c, 2014
ABSTRACT We report a theoretical investigation of strained Ge1−xSnx/Ge (001)-oriented quantum wel... more ABSTRACT We report a theoretical investigation of strained Ge1−xSnx/Ge (001)-oriented quantum wells as a bulding block in active region of infrared photodetector. The electronic band parameters, gaps, discontinuities and effective masses for heterointerfaces between compressively strained Ge1−xSnx and relaxed Ge have beencomputed at room temperature. From this preliminary and mendatory work, we conclude that pseudomorphic Ge1−xSnx alloys become direct band gap semiconductors at a Sn-fraction of 15.3%, e.g. a lattice mismatch as high as 2.3%. Due to achievable critical layer thickness and mainly solid solubility limit, a type-I compressively strained Ge/Ge0.92Sn0.08/Ge (double) quantum well is studied by solving Schrödinger equation without and applied bias voltage. A strong absorption coefficient (> 1×104 cm−1) and a Stark shift of the direct transition between 2.01 μm and 2.25 μm at large external fields (40kV/cm) are attractive characteristics for the design of infrared photodetectors (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Superlattices and Microstructures, 2015
For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge... more For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge/Ge 1-x Sn x /Ge a type-I single quantum wells (SQW) partially strain compensated on Ge 1-y Sn y relaxed layers grown onto (001)-oriented Ge substrate. Such elementary cells with W-like potential profiles of conduction and valence bands have been modeled by solving the one-dimensional Schrödinger equation under an applied external electrical field. First, strain effects on electrons, heavy holes (hh) and light holes (lh) energy bands for strained/relaxed Ge 1-x Sn x /Ge 1-y Sn y heterointerfaces are investigated using the modelsolid theory in the whole ranges (0 x, y 1) of Sn compositions. From the obtained band-discontinuities, band gaps and effective masses, Ge 1-y Sn y /Ge/Ge 0.80 Sn 0.20 /Ge/Ge 1-y Sn y cells are computed as a function of the Ge 0.80 Sn 0.20 well width for three compositions of the Ge 1-y Sn y buffer layer (y=0.05, 0.07 and 0.09) in order to get the optimum quantum confinement of electrons and holes levels while keeping a reasonable amount of averaged strain in the cell. The electric field effect on the absorption spectra is given. An absorption coefficient in the 6 to 3 10 3 cm −1 range is reasonably obtained for a SQW at room temperature with a rather large Stark shift of the direct transition between 0.46 and 0.38 eV (i.e., λ=3.26-2.70 μm) at large external fields (50 kV/cm). These characteristics are attractive for the design of MWIR optical modulators.
Optical Materials, 2015
We theoretically investigate GaAs/Ge/InGaAs as a quantum wells for the design of shortwave infrar... more We theoretically investigate GaAs/Ge/InGaAs as a quantum wells for the design of shortwave infrared p-in photodetectors in which the quantum well Ge/InGaAs is the active region. At room temperature, strained Ge/In x Ga 1Àx As becomes a direct band gap when In composition x is lower than 2.5% and 5% respectively. We have calculated the electronic band parameters for the heterointerface Ge/In x Ga 1Àx As. Then, a type-II strain GaAs/Ge/In 0.35 Ga 0.65 As/GaAs quantum wells heterostructure optimized in terms of compositions and thicknesses is studied by solving Schrödinger equation as well as the absorption coefficient (>1.5 Â 10 4 cm À1). These computations have been used for the study of p-in infrared photodetectors operating at room temperature in the range 1.3-1.55 lm. The electron transport in the GaAs/Ge/In 0.35 Ga 0.65 As/GaAs multi-quantum wells-based p-in structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. The temperature dependence of dark current mechanisms and zero-bias resistance area product (R 0 A) have been analyzed. Extracted from current-voltage characteristics, R 0 A products above 3.6 Á 10 6 X cm 2 at 77 K were calculated, and the quantitative analysis of the J-V curves showed that the dark current density of Ge/In 0.35 Ga 0.65 As photodetector is dominated by generation-recombination processes. The suitability of the modeled photodetector is approved by its feasibility of achieving good device performance near room temperature operating at 1.55 lm.
Modeling and Numerical Simulation of Material Science, 2014
In this paper, a p-in heterojunction based on strain-compensated Si/Si 1−x Ge x /Si multiple quan... more In this paper, a p-in heterojunction based on strain-compensated Si/Si 1−x Ge x /Si multiple quantum wells on relaxed Si 1−y Ge y is proposed for photodetection applications. The Si 1−y Ge y /Si/Si 1−x Ge x /Si/Si 1−y Ge y stack consists in a W-like potential profile strain-compensated in the two low absorption windows of silica fibers infrared (IR) photodetectors. These computations have been used for the study of p-in infrared photodetectors operating at room temperature (RT) in the range 1.3-1.55 μm. The electron transport in the Si/Si 1−x Ge x /Si multi-quantum wells-based p-in structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. These processes were modeled with a system of Schrödinger and kinetic equations self-consistently resolved with the Poisson equation. Temperature dependence of zero-bias resistance area product (R 0 A) and bias-dependent dynamic resistance of the diode have been analyzed in details to investigate the contribution of dark current mechanisms which reduce the electrical performances of the diode.
Computer Physics Communications, 2014
We theoretically study the electron transport through a resonant tunneling diode (RTD) based on s... more We theoretically study the electron transport through a resonant tunneling diode (RTD) based on strained Al x Ga 1−x N/In 0.1 Ga 0.9 N/Al x Ga 1−x N quantum wells embedded in relaxed n-Al 0.15 Ga 0.85 N/strained In 0.1 Ga 0.9 N emitter and collector. The aluminum composition in both injector and collector contacts is taken relatively weak; this does not preclude achieving a wide band offset at the border of the preconfinement wells. The epilayers are assumed with a cubic crystal structure to reduce spontaneous and piezoelectric polarization effects. The resonant tunneling and the thermally activated transfer through the barriers are the two mechanisms of transport taken into account in the calculations based on the Schrödinger, Poisson and kinetic equations resolved self-consistently. Using the transfer matrix formalism, we have analyzed the influence of the double barrier height on the resonant current. With an Al composition in the barriers varying between 30% and 50%, we have found that resonant tunneling dominates over the transport mediated by the thermally activated charge transfer for low applied voltages. It is also found that the designed n-type InGaN/AlGaN RTD with 30% of Al composition in the barriers is a potential candidate for achieving a resonant tunneling diode.
Thin Solid Films, 2008
Self-consistent computations of the potential profile in complex semiconductor heterostructures c... more Self-consistent computations of the potential profile in complex semiconductor heterostructures can be successfully applied for comprehensive simulation of many device characteristics. Such computations have been used for the study of SiGe/Si multiple quantum wells (MQWs) based infrared photodetectors operating in the two low absorption windows of silica fibers, e.g. around λ = 1.3 and λ = 1.55 µm. In this paper, a versatile model is proposed for the design optimization of SiGe/Si MQWs based photodetectors. It is based on the coupled Schrödinger-Poisson equations that allow the determination of the energy quantization levels and the wave functions of charge carriers. The optimum parameters such as the layers thickness, compositions and doping of the relative MQWs based p-in photodetectors under an external applied electric field are determined for the aimed range of wavelength.
Sensor Letters, 2011
ABSTRACT Due to the large variety of properties offered by the binaries of telluride family CdTe,... more ABSTRACT Due to the large variety of properties offered by the binaries of telluride family CdTe, ZnTe, MgTe, HgTe and MnTe as well as their mixed ternary alloys, these materials have been extensively studied but, some points bearing on several properties have never previously reported or are still not clear. In this paper, we report results on the conduction and valence band offsets of the pseudomorphically strained Cd1−x X x Te layer on relaxed Cd1−y X y Te substrate, X = Zn, Hg, Mg and Mn. Based on the Van Der Walle model, calculations have been performed for the all range of material and substrate 0 ≤ x, y ≤ 1. For the CdMnTe diluted magnetic semiconductor which we focus more interest du to its considerable current interest for applications, calculations have been done without and with correction taking into account magnetic effect of magnesium ions Mn++. As it is found that the introduction of only a few percent of Mn into CdTe provides a unique opportunity to combine two important fields in physics, semiconductivity and magnetism. We can take advantage both of possibility of applications in solid-state lasers and exceptional magnetic properties offered by this magnetic diluted semiconductor. This study presents important quantities that are required to model quantum structures and offers a fast and inexpensive way to check device designs and processes.
Sensor Letters, 2011
ABSTRACT The intersubband transition at 1.55 μm wavelength has been demonstrated theoretically in... more ABSTRACT The intersubband transition at 1.55 μm wavelength has been demonstrated theoretically in asymmetric II–VI double quantum wells heterostructures consisting of a deep CdS well and a shallow ZnSe well coupled by a thick BeTe barrier. The intersubband transition allows ultra fast relaxation time. The asymmetric geometry reduces the coupling and then lowers the switching energies. The electronic states of these structures are calculated using the envelope wave function approximation. The transition energies have been studied as a function of CdS and ZnSe well thicknesses. Then the linear and nonlinear optical properties such as optical absorption associated with intersubband transitions have been investigated. The optimum parameters of 1.55 μm photo detector have been determined at 300 K.
Sensor Letters, 2011
ABSTRACT III-V quantum well structures are now the subject of increasing number of studies due to... more ABSTRACT III-V quantum well structures are now the subject of increasing number of studies due to their applications in optoelectronic devices. We have calculated the electronic band parameters for Al-x Ga1-xAsySb1-y/GaSb. Thus and using the model solid theory, strain effects on heavy holes (hh), light holes (lh) and split off (so) are investigated as function of Aluminum and arsenic compositions in the hole range 0 <= x, y <= 1. Taking into account these results and based on a one dimensional Shrodinguer equation, we report a calculation of the quantum confinement of electron and heavy-hole levels for Ga1-xInxAsySb1-y/AlxGa1-xAsySb1-y. Our results provide useful information for the design of heterostructure emitting near 3 mu m.
Physica E: Low-dimensional Systems and Nanostructures, 2009
It has been a long time since the start of successful production in laboratory of light-emitting ... more It has been a long time since the start of successful production in laboratory of light-emitting devices based on wide bandgap II–VI semiconductors, but the applications have been limited by the luck of materials that can emit blue light efficiently. In this work, we propose and model a ZnSxSe1−x-based structure emitting blue light and resolve many defect problems due to
Optik, 2013
The effect of well and barrier widths on optical properties of intersubband transitions in asymme... more The effect of well and barrier widths on optical properties of intersubband transitions in asymmetric (CdS/ZnSe) quantum wells have been investigated theoretically. The electronic states in these structures are calculated using both the envelope wave function approximation and the compact-density matrix formalism. The obtained results reveal that the linear and nonlinear properties have non-monotonic behavior with these parameters. It is found that the optical absorption and the refractive index change are greater in asymmetric double quantum well than that of symmetric heterostructure. These results suggest that the absorption process can be easily controlled by the structure parameters of an asymmetric rectangular quantum well. Thus, our results can be useful for electro-optical modulators and photodetectors in the infrared region.
Materials Science in Semiconductor Processing, 2006
SiGe/Si resonant tunneling diodes (RTDs) grown on relaxed n-Ge 0.3 Si 0.7 virtual substrates are ... more SiGe/Si resonant tunneling diodes (RTDs) grown on relaxed n-Ge 0.3 Si 0.7 virtual substrates are attractive devices for lowpower/high-frequency applications compatible with Si-CMOS technology. With the intention to improve the performances of n-type RTDs build-on Si 0.4 Ge 0.6 /Si/Si 0.4 Ge 0.6 double barriers, we consider graded Si 1Àx Ge x (x ¼ 0.3-0.0) spacers (triangular quantum wells) for injection and collection of electrons. Graded layer composition, implanted for the lattice mismatch growth of many semiconductors, has offered significant improvement in the epilayer quality and hence was used for many advanced electronic and optoelectronic applications. The modeled design is aimed to further reduce the voltage at which peak-current density is achieved and to increase the current-peak to valley ratio. We report a numerical solution of the conduction-band profile by solving self-consistently Schro¨dinger and Poisson equations without and with an applied electric field. An analysis of the Stark effect on electronic levels is made. Two main features have been extrapolated: (i) a charge transfer can occur due to the tunneling effect, and this charge transfer tends to saturate as the applied electric field increases; (ii) the middle quantum well is populated compared with common RTD having an abrupt Si spacer (squared quantum wells).
Materials Science in Semiconductor Processing, 2014
In this paper, we report on the design and characterization of a quantum well based infrared phot... more In this paper, we report on the design and characterization of a quantum well based infrared photodetectors covering simultaneously infrared radiation within mid-and longinfrared spectral regions. The proposed infrared photodetectors rely on intersubband transitions in asymmetric ZnSe/CdS double quantum wells. The three-energy-level and the wavelengths of the intersubband transitions in the asymmetric double quantum wells are obtained by solving the Schrödinger and Poisson equations self consistently, the influence of the right well width on the absorption coefficient is studied. The peak positions of intersubband absorption coefficients in the structure are found at 3.31, 4.4 and 13.5 mm for a 1 nm right well width while the absorption peak positions are located at 3.33, 6.43 and 6.95 mm for a 1.4 nm right well thickness. Then, the electro-optic performances of the infrared photodetector are evaluated; the dark current dependence with the applied voltage and temperature is discussed. This work demonstrates the possibility of detection of widely separated wavelength bands using intersubband transitions in quantum wells with a low dark current.
Materials Science and Engineering: C, 2006
ABSTRACT A theoretical analysis, using a Schrödinger solver, is made to calculate the electric fi... more ABSTRACT A theoretical analysis, using a Schrödinger solver, is made to calculate the electric field-dependent interband transitions in a Si/Si1−xGex/Si double QW strain-compensated in relaxed Si1−yGey barriers. The conduction and the valence band present a W-like potential profile, resulting in a quasi-type I heterostructure. Three peculiar features are revealed as the electric field is increased: (i) two uncoupled e11 and e12 electron levels are generated, (ii) the e11–hh1 fundamental transition due to first silicon QW exhibits a red shift in emission energy while the e12–hh1 transition energy is bleu shifted, (iii) an improved wave function overlap for the e11–h1 fundamental transition, the latter property showing the advantage having two adjacent QWs in this W architecture.
Materials Science and Engineering: B, 2005
We report on optoelectronic properties of devices based on Si/Si1−xGex systems. To limit the inhe... more We report on optoelectronic properties of devices based on Si/Si1−xGex systems. To limit the inherent problems of the type II character and the indirect nature of the bandgap, we propose Si/Si1−xGex strained QWs embedded in relaxed Si1−yGey barriers. The conduction and the valence band present a W-, Usami- or M-like potential profile with a quasi-type I heterostructures. Based on Schrödinger
Materials Science and Engineering: B, 2005
... [1] and now, resonant tunneling diodes (RTDs) are a mature technology in the IIIV system wit... more ... [1] and now, resonant tunneling diodes (RTDs) are a mature technology in the IIIV system with many demonstrations of memory [2] and logic circuits [3]. In IIVI semiconductors, resonant tunneling has been realized in narrow-gap [4] and in wide-gap [5] systems. ...
Journal of Physics: Condensed Matter, 2006
II-VI quantum well (QW) structures are now the subject of an increasing number of studies due to ... more II-VI quantum well (QW) structures are now the subject of an increasing number of studies due to their applications in optoelectronics. Following our recent calculations showing that the fundamental gap of ZnSxSe1-x presents a minimum for sulfur molar fraction x = 0.20, an accurate knowledge of band offsets for these ternary alloys will be useful to model devices based on
The European Physical Journal B, 2005
In view of the fact that the bandwidth required in optical fiber communication systems will excee... more In view of the fact that the bandwidth required in optical fiber communication systems will exceed 100 Gb s −1 , ultrafast optical switching and modulation devices with high efficiency must be developed. Given that intersubband transitions (ISBT) in quantum wells (QWs) are one of the important ultrafast phenomena, a numerical study of intersubband transition (ISBT) properties in (CdS/ZnSe)/BeTe QWs is considered. The structure modeled consists of a few monolayers of CdS embedded in a ZnSe/BeTe QW. A self-consistent analysis is made to achieve the desired properties and device applications. Variation of CdS well thickness leads to tailoring of the band alignment, achieving optical transitions in the wavelength range of 1.33-1.55 µm wavelengths for applications in optical fiber transmission. To analyze the optical behavior of the heterostructure under investigation, we have calculated the CdS well thickness-dependant oscillator strengths and electron emission energy of the intersubband transition between the two first states in the well. An attempt to explain our results will be presented.
physica status solidi c, 2014
ABSTRACT We report a theoretical investigation of strained Ge1−xSnx/Ge (001)-oriented quantum wel... more ABSTRACT We report a theoretical investigation of strained Ge1−xSnx/Ge (001)-oriented quantum wells as a bulding block in active region of infrared photodetector. The electronic band parameters, gaps, discontinuities and effective masses for heterointerfaces between compressively strained Ge1−xSnx and relaxed Ge have beencomputed at room temperature. From this preliminary and mendatory work, we conclude that pseudomorphic Ge1−xSnx alloys become direct band gap semiconductors at a Sn-fraction of 15.3%, e.g. a lattice mismatch as high as 2.3%. Due to achievable critical layer thickness and mainly solid solubility limit, a type-I compressively strained Ge/Ge0.92Sn0.08/Ge (double) quantum well is studied by solving Schrödinger equation without and applied bias voltage. A strong absorption coefficient (> 1×104 cm−1) and a Stark shift of the direct transition between 2.01 μm and 2.25 μm at large external fields (40kV/cm) are attractive characteristics for the design of infrared photodetectors (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Superlattices and Microstructures, 2015
For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge... more For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge/Ge 1-x Sn x /Ge a type-I single quantum wells (SQW) partially strain compensated on Ge 1-y Sn y relaxed layers grown onto (001)-oriented Ge substrate. Such elementary cells with W-like potential profiles of conduction and valence bands have been modeled by solving the one-dimensional Schrödinger equation under an applied external electrical field. First, strain effects on electrons, heavy holes (hh) and light holes (lh) energy bands for strained/relaxed Ge 1-x Sn x /Ge 1-y Sn y heterointerfaces are investigated using the modelsolid theory in the whole ranges (0 x, y 1) of Sn compositions. From the obtained band-discontinuities, band gaps and effective masses, Ge 1-y Sn y /Ge/Ge 0.80 Sn 0.20 /Ge/Ge 1-y Sn y cells are computed as a function of the Ge 0.80 Sn 0.20 well width for three compositions of the Ge 1-y Sn y buffer layer (y=0.05, 0.07 and 0.09) in order to get the optimum quantum confinement of electrons and holes levels while keeping a reasonable amount of averaged strain in the cell. The electric field effect on the absorption spectra is given. An absorption coefficient in the 6 to 3 10 3 cm −1 range is reasonably obtained for a SQW at room temperature with a rather large Stark shift of the direct transition between 0.46 and 0.38 eV (i.e., λ=3.26-2.70 μm) at large external fields (50 kV/cm). These characteristics are attractive for the design of MWIR optical modulators.
Optical Materials, 2015
We theoretically investigate GaAs/Ge/InGaAs as a quantum wells for the design of shortwave infrar... more We theoretically investigate GaAs/Ge/InGaAs as a quantum wells for the design of shortwave infrared p-in photodetectors in which the quantum well Ge/InGaAs is the active region. At room temperature, strained Ge/In x Ga 1Àx As becomes a direct band gap when In composition x is lower than 2.5% and 5% respectively. We have calculated the electronic band parameters for the heterointerface Ge/In x Ga 1Àx As. Then, a type-II strain GaAs/Ge/In 0.35 Ga 0.65 As/GaAs quantum wells heterostructure optimized in terms of compositions and thicknesses is studied by solving Schrödinger equation as well as the absorption coefficient (>1.5 Â 10 4 cm À1). These computations have been used for the study of p-in infrared photodetectors operating at room temperature in the range 1.3-1.55 lm. The electron transport in the GaAs/Ge/In 0.35 Ga 0.65 As/GaAs multi-quantum wells-based p-in structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. The temperature dependence of dark current mechanisms and zero-bias resistance area product (R 0 A) have been analyzed. Extracted from current-voltage characteristics, R 0 A products above 3.6 Á 10 6 X cm 2 at 77 K were calculated, and the quantitative analysis of the J-V curves showed that the dark current density of Ge/In 0.35 Ga 0.65 As photodetector is dominated by generation-recombination processes. The suitability of the modeled photodetector is approved by its feasibility of achieving good device performance near room temperature operating at 1.55 lm.
Modeling and Numerical Simulation of Material Science, 2014
In this paper, a p-in heterojunction based on strain-compensated Si/Si 1−x Ge x /Si multiple quan... more In this paper, a p-in heterojunction based on strain-compensated Si/Si 1−x Ge x /Si multiple quantum wells on relaxed Si 1−y Ge y is proposed for photodetection applications. The Si 1−y Ge y /Si/Si 1−x Ge x /Si/Si 1−y Ge y stack consists in a W-like potential profile strain-compensated in the two low absorption windows of silica fibers infrared (IR) photodetectors. These computations have been used for the study of p-in infrared photodetectors operating at room temperature (RT) in the range 1.3-1.55 μm. The electron transport in the Si/Si 1−x Ge x /Si multi-quantum wells-based p-in structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. These processes were modeled with a system of Schrödinger and kinetic equations self-consistently resolved with the Poisson equation. Temperature dependence of zero-bias resistance area product (R 0 A) and bias-dependent dynamic resistance of the diode have been analyzed in details to investigate the contribution of dark current mechanisms which reduce the electrical performances of the diode.
Computer Physics Communications, 2014
We theoretically study the electron transport through a resonant tunneling diode (RTD) based on s... more We theoretically study the electron transport through a resonant tunneling diode (RTD) based on strained Al x Ga 1−x N/In 0.1 Ga 0.9 N/Al x Ga 1−x N quantum wells embedded in relaxed n-Al 0.15 Ga 0.85 N/strained In 0.1 Ga 0.9 N emitter and collector. The aluminum composition in both injector and collector contacts is taken relatively weak; this does not preclude achieving a wide band offset at the border of the preconfinement wells. The epilayers are assumed with a cubic crystal structure to reduce spontaneous and piezoelectric polarization effects. The resonant tunneling and the thermally activated transfer through the barriers are the two mechanisms of transport taken into account in the calculations based on the Schrödinger, Poisson and kinetic equations resolved self-consistently. Using the transfer matrix formalism, we have analyzed the influence of the double barrier height on the resonant current. With an Al composition in the barriers varying between 30% and 50%, we have found that resonant tunneling dominates over the transport mediated by the thermally activated charge transfer for low applied voltages. It is also found that the designed n-type InGaN/AlGaN RTD with 30% of Al composition in the barriers is a potential candidate for achieving a resonant tunneling diode.
Thin Solid Films, 2008
Self-consistent computations of the potential profile in complex semiconductor heterostructures c... more Self-consistent computations of the potential profile in complex semiconductor heterostructures can be successfully applied for comprehensive simulation of many device characteristics. Such computations have been used for the study of SiGe/Si multiple quantum wells (MQWs) based infrared photodetectors operating in the two low absorption windows of silica fibers, e.g. around λ = 1.3 and λ = 1.55 µm. In this paper, a versatile model is proposed for the design optimization of SiGe/Si MQWs based photodetectors. It is based on the coupled Schrödinger-Poisson equations that allow the determination of the energy quantization levels and the wave functions of charge carriers. The optimum parameters such as the layers thickness, compositions and doping of the relative MQWs based p-in photodetectors under an external applied electric field are determined for the aimed range of wavelength.
Sensor Letters, 2011
ABSTRACT Due to the large variety of properties offered by the binaries of telluride family CdTe,... more ABSTRACT Due to the large variety of properties offered by the binaries of telluride family CdTe, ZnTe, MgTe, HgTe and MnTe as well as their mixed ternary alloys, these materials have been extensively studied but, some points bearing on several properties have never previously reported or are still not clear. In this paper, we report results on the conduction and valence band offsets of the pseudomorphically strained Cd1−x X x Te layer on relaxed Cd1−y X y Te substrate, X = Zn, Hg, Mg and Mn. Based on the Van Der Walle model, calculations have been performed for the all range of material and substrate 0 ≤ x, y ≤ 1. For the CdMnTe diluted magnetic semiconductor which we focus more interest du to its considerable current interest for applications, calculations have been done without and with correction taking into account magnetic effect of magnesium ions Mn++. As it is found that the introduction of only a few percent of Mn into CdTe provides a unique opportunity to combine two important fields in physics, semiconductivity and magnetism. We can take advantage both of possibility of applications in solid-state lasers and exceptional magnetic properties offered by this magnetic diluted semiconductor. This study presents important quantities that are required to model quantum structures and offers a fast and inexpensive way to check device designs and processes.
Sensor Letters, 2011
ABSTRACT The intersubband transition at 1.55 μm wavelength has been demonstrated theoretically in... more ABSTRACT The intersubband transition at 1.55 μm wavelength has been demonstrated theoretically in asymmetric II–VI double quantum wells heterostructures consisting of a deep CdS well and a shallow ZnSe well coupled by a thick BeTe barrier. The intersubband transition allows ultra fast relaxation time. The asymmetric geometry reduces the coupling and then lowers the switching energies. The electronic states of these structures are calculated using the envelope wave function approximation. The transition energies have been studied as a function of CdS and ZnSe well thicknesses. Then the linear and nonlinear optical properties such as optical absorption associated with intersubband transitions have been investigated. The optimum parameters of 1.55 μm photo detector have been determined at 300 K.
Sensor Letters, 2011
ABSTRACT III-V quantum well structures are now the subject of increasing number of studies due to... more ABSTRACT III-V quantum well structures are now the subject of increasing number of studies due to their applications in optoelectronic devices. We have calculated the electronic band parameters for Al-x Ga1-xAsySb1-y/GaSb. Thus and using the model solid theory, strain effects on heavy holes (hh), light holes (lh) and split off (so) are investigated as function of Aluminum and arsenic compositions in the hole range 0 <= x, y <= 1. Taking into account these results and based on a one dimensional Shrodinguer equation, we report a calculation of the quantum confinement of electron and heavy-hole levels for Ga1-xInxAsySb1-y/AlxGa1-xAsySb1-y. Our results provide useful information for the design of heterostructure emitting near 3 mu m.
Physica E: Low-dimensional Systems and Nanostructures, 2009
It has been a long time since the start of successful production in laboratory of light-emitting ... more It has been a long time since the start of successful production in laboratory of light-emitting devices based on wide bandgap II–VI semiconductors, but the applications have been limited by the luck of materials that can emit blue light efficiently. In this work, we propose and model a ZnSxSe1−x-based structure emitting blue light and resolve many defect problems due to
Optik, 2013
The effect of well and barrier widths on optical properties of intersubband transitions in asymme... more The effect of well and barrier widths on optical properties of intersubband transitions in asymmetric (CdS/ZnSe) quantum wells have been investigated theoretically. The electronic states in these structures are calculated using both the envelope wave function approximation and the compact-density matrix formalism. The obtained results reveal that the linear and nonlinear properties have non-monotonic behavior with these parameters. It is found that the optical absorption and the refractive index change are greater in asymmetric double quantum well than that of symmetric heterostructure. These results suggest that the absorption process can be easily controlled by the structure parameters of an asymmetric rectangular quantum well. Thus, our results can be useful for electro-optical modulators and photodetectors in the infrared region.
Materials Science in Semiconductor Processing, 2006
SiGe/Si resonant tunneling diodes (RTDs) grown on relaxed n-Ge 0.3 Si 0.7 virtual substrates are ... more SiGe/Si resonant tunneling diodes (RTDs) grown on relaxed n-Ge 0.3 Si 0.7 virtual substrates are attractive devices for lowpower/high-frequency applications compatible with Si-CMOS technology. With the intention to improve the performances of n-type RTDs build-on Si 0.4 Ge 0.6 /Si/Si 0.4 Ge 0.6 double barriers, we consider graded Si 1Àx Ge x (x ¼ 0.3-0.0) spacers (triangular quantum wells) for injection and collection of electrons. Graded layer composition, implanted for the lattice mismatch growth of many semiconductors, has offered significant improvement in the epilayer quality and hence was used for many advanced electronic and optoelectronic applications. The modeled design is aimed to further reduce the voltage at which peak-current density is achieved and to increase the current-peak to valley ratio. We report a numerical solution of the conduction-band profile by solving self-consistently Schro¨dinger and Poisson equations without and with an applied electric field. An analysis of the Stark effect on electronic levels is made. Two main features have been extrapolated: (i) a charge transfer can occur due to the tunneling effect, and this charge transfer tends to saturate as the applied electric field increases; (ii) the middle quantum well is populated compared with common RTD having an abrupt Si spacer (squared quantum wells).
Materials Science in Semiconductor Processing, 2014
In this paper, we report on the design and characterization of a quantum well based infrared phot... more In this paper, we report on the design and characterization of a quantum well based infrared photodetectors covering simultaneously infrared radiation within mid-and longinfrared spectral regions. The proposed infrared photodetectors rely on intersubband transitions in asymmetric ZnSe/CdS double quantum wells. The three-energy-level and the wavelengths of the intersubband transitions in the asymmetric double quantum wells are obtained by solving the Schrödinger and Poisson equations self consistently, the influence of the right well width on the absorption coefficient is studied. The peak positions of intersubband absorption coefficients in the structure are found at 3.31, 4.4 and 13.5 mm for a 1 nm right well width while the absorption peak positions are located at 3.33, 6.43 and 6.95 mm for a 1.4 nm right well thickness. Then, the electro-optic performances of the infrared photodetector are evaluated; the dark current dependence with the applied voltage and temperature is discussed. This work demonstrates the possibility of detection of widely separated wavelength bands using intersubband transitions in quantum wells with a low dark current.
Materials Science and Engineering: C, 2006
ABSTRACT A theoretical analysis, using a Schrödinger solver, is made to calculate the electric fi... more ABSTRACT A theoretical analysis, using a Schrödinger solver, is made to calculate the electric field-dependent interband transitions in a Si/Si1−xGex/Si double QW strain-compensated in relaxed Si1−yGey barriers. The conduction and the valence band present a W-like potential profile, resulting in a quasi-type I heterostructure. Three peculiar features are revealed as the electric field is increased: (i) two uncoupled e11 and e12 electron levels are generated, (ii) the e11–hh1 fundamental transition due to first silicon QW exhibits a red shift in emission energy while the e12–hh1 transition energy is bleu shifted, (iii) an improved wave function overlap for the e11–h1 fundamental transition, the latter property showing the advantage having two adjacent QWs in this W architecture.
Materials Science and Engineering: B, 2005
We report on optoelectronic properties of devices based on Si/Si1−xGex systems. To limit the inhe... more We report on optoelectronic properties of devices based on Si/Si1−xGex systems. To limit the inherent problems of the type II character and the indirect nature of the bandgap, we propose Si/Si1−xGex strained QWs embedded in relaxed Si1−yGey barriers. The conduction and the valence band present a W-, Usami- or M-like potential profile with a quasi-type I heterostructures. Based on Schrödinger
Materials Science and Engineering: B, 2005
... [1] and now, resonant tunneling diodes (RTDs) are a mature technology in the IIIV system wit... more ... [1] and now, resonant tunneling diodes (RTDs) are a mature technology in the IIIV system with many demonstrations of memory [2] and logic circuits [3]. In IIVI semiconductors, resonant tunneling has been realized in narrow-gap [4] and in wide-gap [5] systems. ...
Journal of Physics: Condensed Matter, 2006
II-VI quantum well (QW) structures are now the subject of an increasing number of studies due to ... more II-VI quantum well (QW) structures are now the subject of an increasing number of studies due to their applications in optoelectronics. Following our recent calculations showing that the fundamental gap of ZnSxSe1-x presents a minimum for sulfur molar fraction x = 0.20, an accurate knowledge of band offsets for these ternary alloys will be useful to model devices based on