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ABSTRACT: A theoretical investigation of a GaAs/AlGaAs-material-system-based four quantum well infrared detector structures consisting
of ten periods of three asymmetric quantum well units are presented. Each quantum well in the units is sensitive to wavelengths
of 8.75, 10, and 11.75 μm, respectively. The effect of the barrier thicknesses on the responsivity spectra is discussed with
respect to barrier transmissions under negative and positive bias voltages. Each detector structure shows voltage-tunable
broadband and multicolor features in 8–12-μm long wavelength infrared range (LWIR).
Applied Physics A 04/2012; 98(2):269-273. · 1.63 Impact Factor
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ABSTRACT: We investigate the theoretical calculations of the voltage tunable dual-band quantum-well infrared photodetector (QWIP) in the long and very long wavelength infrared range (LWIR and VLWIR). The detector consists of two serially connected GaAs/AlGaAs stacks which have spectral responses of 8.4- and 14- μm wavelengths, respectively. The peak responsivity wavelength of the stacks shifts from 8.4 to 14 μm as the bias voltage is increased.
IEEE Photonics Technology Letters 11/2011; · 2.19 Impact Factor
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ABSTRACT: The binding energy of a hydrogen-like impurity in an ellipsoidal parabolic quantum dot under the magnetic and electric fields have been discussed by using the effective mass approximation and the variational method. We have calculated the effects of the magnetic and electric fields on the binding energy of donor impurities in the quantum dots with different confinement potentials. We conclude that the structural confinement is very effective, and especially in the weak confinement potential case the magnetic field dependence of the donor binding energy is more pronounced.
Surface Review and Letters (SRL). 01/2008; 15(03):201-205.
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ABSTRACT: A theoretical investigation of a GaAs-AlGaAs infrared detector consisting of three asymmetric quantum wells is presented. Each quantum well is sensitive to yield absorption and a photoresponse at peak wavelengths of 8 mum, 9.5 mum and 10.8 mum respectively. Device operation is based on inter-subband bound-to-bound transition. Asymmetry in the quantum wells is shown to give broad band responsivity spectrum at an operating bias.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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ABSTRACT: We present a theoretical investigation of a GaAs/AlGaAs infrared detector consisting of three asymmetric quantum wells. Each well is designed to yield absorption and a photoresponse at peak wavelengths of 8.2 µm, 9.5 µm and 10.8 µm respectively. The device operation is based on an intersubband bound to quasi-bound transition. Asymmetry in the barriers is shown to give rise to the dependence of the spectral line width on applied reverse bias.
Semiconductor Science and Technology 03/2007; 22(4):422. · 1.72 Impact Factor
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ABSTRACT: We present a theoretical investigation of a staircase-like quantum well infrared photodetector (QWIP). It detects wavelength between 7.6 μm and 13.5 μm range at an applied electric field of F = 1.9x104 V/cm at 77 K. The dark current density was found to be around 2x10–7 A/cm2 at operating bias, which is lower than the conventional QWIPs in the literature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (c) 02/2007; 4(2):607 - 610.
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ABSTRACT: In this study, we have calculated the donor impurity binding energy, donor impurity related photoionization cross-section and polarizability in symmetric GaAs/Ga1–xAlxAs quantum well-wire as a function of the impurity positions, dimensions of the structures and external electric and magnetic field, the calculations were performed within the effective mass approximation, using a variational method. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (c) 02/2007; 4(2):332 - 335.
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ABSTRACT: The laser-field dependence of the impurity binding energy and donor-related photoionization cross-section in graded quantum-well wire under an external static electric field is calculated by a variational method and in the effective mass approximation. We have shown that, in the graded quantum-well wire structures, not only the 'dressed' potential but also the applied direction of the external electric field plays a very important role in the determination of the binding energy.
Journal of Physics Condensed Matter 06/2006; 18(27):6263. · 2.55 Impact Factor
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ABSTRACT: We present a theoretical investigation of a novel staircase-like quantum well infrared photodetector (QWIP). It detects wavelengths between 8.8 lm and 12.3 lm at an applied electric field of F = 6 · 10 4 V/cm at room temperature. Device operation is based on inter-subband bound to continuum transition. We also calculated the responsivity at room temper-ature and dark current density at 77 K. The dark current density was found to be around 10 À8 A/cm 2 at operating bias, which is lower than the conventional QWIPs in the literature.
12/2005;
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ABSTRACT: We present a theoretical investigation of a novel staircase-like quantum well infrared photodetector (QWIP). The proposed structure makes use of quantum wells and barriers with increasing Al content both in the wells and in the barriers forming a staircase-like energy band diagram without applied bias. The detection wavelength is around k = 12 lm at an applied electric field of F = 1.4 · 10 4 V/cm at room temperature. Device operation is based on inter-subband bound-to-bound transition. We have solved the energy band diagram of the structure self-consistently. We have also calculated the absorption coefficient, responsivity, total net quantum efficiency and dark current density at room temperature. The dark current density at the operating field was found to be around 10 À2 A/cm 2 , which is lower than the conventional QWIPs in the literature.
11/2005;
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ABSTRACT: For Eqs. (2a) and (2b) of the original article the correct versions are given. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 10/2005; 242(14):2976 - 2976. · 1.32 Impact Factor
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ABSTRACT: The laser field dependence of the intersubband optical absorption in a graded quantum well (GQW), under an applied electric field is calculated in the effective mass approximation. We have theoretically shown that, in the GQW structures, not only the 'dressed' potential but also the direction of the external electric field plays a very important role in the intersubband transitions.
Journal of Physics D Applied Physics 03/2005; 38(6):935. · 2.54 Impact Factor
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ABSTRACT: An intense laser field effect on the intersubband transitions in quantum wells is theoretically investigated within the framework of the effective-mass approximation. Results obtained show that intersubbband optical transitions and energy levels in quantum wells can be significantly modified and controlled by an intense laser field.
Applied Physics A 01/2005; 80(3):541-544. · 1.63 Impact Factor
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ABSTRACT: The intersubband absorption in square and graded quantum wells under a laser field is calculated within the framework of the effective mass approximation. We conclude that, for quantum wells with different shapes, the laser field amplitude induces an important effect on the electronic and optical properties of the semiconductor structure. This gives a new degree of freedom in various device applications based on the intersubband transition of electrons.
21.Fg. 07/2004; 73(78).
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ABSTRACT: The binding energy of the donor impurity in double triangle quantum well (DTQW), double graded (DGQW) and double square (DSQW) GaAs–(Ga,Al)As quantum wells under the electric field is calculated by using a variational approach. The results have been obtained in the presence electric field applied along the growth direction as a function of the impurity position, barrier width and the geometric shape of the double quantum wells. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 03/2004; 241(5):1066 - 1072. · 1.32 Impact Factor
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ABSTRACT: For different applied electric fields the intersubband transitions of double Si δ-doped GaAs structures are theoretically investigated for a uniform donor distribution. The electronic structure has been calculated by solving the Schrödinger and Poisson equations self-consistently. It is found that the changes of the confining potential, the subband energies and intersubband optical absorption are quite sensitive to the applied electric field. Different from the single δ-doped structure, we have seen the abrupt changing of the subband energies and the absorption coefficient whenever the applied electric field reaches two certain values. While for the (1–2) intersubband transition, the intersubband absorption spectrum shows blueshifts up to the first critical electric field value, this spectrum shows redshifts up to the second critical electric field value and shows blueshifts for higher electric fields than the second critical field values. This behavior in the intersubband transitions for different electric fields can be used in some infrared optical device applications based on the intersubband transitions of electrons.
Superlattices and Microstructures 01/2004; 35:95-104. · 1.49 Impact Factor
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ABSTRACT: For the uniform distribution we have theoretically investigated the influence of donor thickness on two coupled Si -doped GaAs structure, at T=0K. Electronic structure have been calculated by solving the Schrdinger and Poisson equations self-consistently. We thus find the confining potential, the electronic density, the subband energies and their eigen envelope functions, the subband occupations and Fermi energy. From the self-consistent calculation, we have seen that the effective potential profile and the electronic density of two coupled Si -doped GaAs structure are sensitive to the donor thickness while the subband energies and the subband occupations are not sensitive to the donor thickness .
Applied Physics A 07/2003; 77(3):427-431. · 1.63 Impact Factor
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ABSTRACT: Using a variational method and within the effective mass approximation, we calculate the laser-field dependence of binding energy and the polarizability of shallow-donor impurities in graded quantum wells under an external static electric field. We have shown that, in the graded quantum well structures, not only the 'dressed' potential but also the direction of the external electric field parallel to the growth direction play very important roles in the determination of the binding energy and the polarizability of a hydrogenic impurity.
Semiconductor Science and Technology 04/2003; 18(6):470. · 1.72 Impact Factor
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ABSTRACT: We have theoretically investigated the electronic structure of two coupled Si d-doped GaAs at T ¼ 0 K. For the uniform donor distribution we have studied the influence of donor concentration on the subband structure. In order to obtain the electronic structure we have calculated self-consistently the Schr . odinger and Poisson equations. From the self-consistent calculation, we have seen that the electronic structure is quite sensitive to the donor concentration and the d-layer separation. Under the assumption that the mobility is limited by the overlap of the wave function and the ionized scattering centers we can estimate that the mobility in single d-doped structures is very low compared to closely spaced coupled d-doped GaAs structures. r 2003 Elsevier Science B.V. All rights reserved.
Physica B. 01/2003; 334:1-8.
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ABSTRACT: We have calculated the subbands in the GaAs quantum well at the n-side of the junction in a Ga 1−x Al x As diode. We show that the density of carriers confined in the quantum well increases by the increasing magnetic field strength but also decreases depending on the magnetic length. We have observed oscillatory behavior of the density of carriers due to the in-plane magnetic field.
Superlattices and Microstructures 01/2003; 33:235-245. · 1.49 Impact Factor
