The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
M. Geddo - One of the best experts on this subject based on the ideXlab platform.
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Photoreflectance and reflectance investigation of deuterium-irradiated GaAsN
Applied Physics Letters, 2007Co-Authors: M. Geddo, Maddalena Patrini, T. Ciabattoni, Giorgio Guizzetti, Matteo Galli, Antonio Polimeni, Rinaldo Trotta, Mario Capizzi, G. Bais, M. PiccinAbstract:The effect of deuterium irradiation on the optical and strain properties of GaAsN∕GaAs heterostructures was investigated by Photoreflectance and reflectance techniques. The strain occurring in as-grown and deuterated GaAsN layers is monitored and measured by means of Photoreflectance spectroscopy, highlighting the strain inversion after irradiation. By combining static and modulated reflectance results, evidence is given that the deuterium-induced recovery of the GaAs band gap as well as the strain inversion in GaAsN layers are accompanied by a 0.4%–0.8% reduction of the refractive index in the 1.31 and 1.55μm spectral windows of interest for fiber optic communications. These results anticipate a single step process to an in-plane confinement of carriers and photons.
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Studies of Photoreflectance spectra in Cd1−xMnxTe/CdTe superlattices with high compositions
Journal of Applied Physics, 2002Co-Authors: Chenjia Chen, Xuezhong Wang, Xiaogan Liang, Silvia Tavazzi, Alessandro Borghesi, Adele Sassella, Vittorio Bellani, M. Geddo, A. StellaAbstract:Cd1−xMnxTe/CdTe superlattices were grown by molecular beam epitaxy with a CdTe buffer layer on GaAs(001) substrate. Photoreflectance spectra were performed on Cd1−xMnxTe/CdTe superlattices with high compositions of x=0.4, 0.8 at room temperature and liquid nitrogen temperature. The exciton transitions related to the heavy (H) and light (L) holes of 11H, 11L, 22H, and 33H are observed. After taking into account the strain-induced and quantum confinement effects, the theoretical calculations are in good agreement with the Photoreflectance measurement results except x=0.8 of 33H. Photoluminescence measurements were also performed at room temperature and low temperature in order to compare with our Photoreflectance results. Our results show that the Photoreflectance spectroscopy technique is a powerful probe for the study of quantized state structures in superlattices systems.
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Photoreflectance of GaSb/Al0.4Ga0.6Sb single quantum wells
Applied Physics Letters, 1998Co-Authors: M. Geddo, S. Franchi, R. Ferrini, Maddalena Patrini, Andrea Baraldi, R. MagnaniniAbstract:We report a Photoreflectance study conducted in the 0.7–1.2 eV photon energy range and at temperatures from 80 to 300 K of GaSb/Al0.4Ga0.6Sb single quantum wells grown by molecular beam epitaxy. We observed clear and well-resolved structures, which could be attributed to the interband optical transitions originating in both the GaSb buffer and the quantum wells, and which could be fitted by standard critical-point line shapes. Our results demonstrate that even unintentionally doped GaSb-based quantum systems can be studied and characterized by Photoreflectance, especially at low temperatures.
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Photoreflectance versus photoluminescence in strain induced quantum well wires
Solid State Communications, 1996Co-Authors: M. Geddo, A. Stella, S. Di Lernia, A. Bosacchi, S. Franchi, M. Gentili, D. PeschiaroliAbstract:Photoreflectance vs photoluminescence measurements of stress-induced quantum wires, obtained by patterning an InGaAs layer pseudomorphic grown on a GaAs well in wire-shaped stressors, are presented and compared. An excellent agreement was found between the experimental results obtained with the two techniques about the lateral confinement of the carriers and evidence is given at room temperature of quantization in two directions by means of Photoreflectance.
R Kudrawiec - One of the best experts on this subject based on the ideXlab platform.
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Localized and delocalized states in GaNAs studied by microphotoluminescence and Photoreflectance
Applied Physics Letters, 2009Co-Authors: R Kudrawiec, Grzegorz Sęk, Jan Misiewicz, Fumitaro Ishikawa, Achim Trampert, Klaus H. PloogAbstract:Optical transitions in GaNAs bulk layer containing 2.2% N have been studied with microphotoluminescence (μ-PL) and Photoreflectance. At low temperatures and low excitation conditions, the μ-PL spectra showed sharp PL lines of 100–300μeV widths about 10–20meV below the energy gap. Those lines were attributed to the recombination of localized excitons trapped at local potential minima. When the excitation power was increased, an additional smooth PL band appeared at the higher-energy side. This band corresponds to the light-hole transition in Photoreflectance spectrum, i.e., transition between the delocalized states.
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investigation of the non square ingaasp inp quantum wells in the electric field by Photoreflectance
Acta Physica Polonica A, 2002Co-Authors: R Kudrawiec, J. Misiewicz, G Sek, W Rudnorudzinski, J Wojcik, B J Robinson, D A Thompson, P MascherAbstract:Non-square quantum wells in electric field have been investigated by Photoreflectance and photoluminescence spectroscopies. The structures have been obtained by a post-growth modification (rapid thermal annealing) of standard 1.55 μm InGaAsP-based laser structures that were grown by gas source molecular beam epitaxy. During rapid thermal annealing a migration of semiconductor atoms across quantum well interfaces changes the quantum well profile from a square well to a rounded well. The modification of the profile changes energy levels in the quantum well and in consequence a blue shift of the quantum well emission peak is observed in photoluminescence. In this paper the blue shift of the ground state transition of post-growth modified quantum well structures has been investigated by both photoluminescence and Photoreflectance techniques. Also a blue shift of excited state transitions has been observed in Photoreflectance spectra. Generally, a stronger blue shift for the ground state transition than for excited state transitions has been observed. Additionally, oscillator strengths for all quantum well transitions have been determined from Photoreflectance spectra. It has been found that the oscillator strength is constant for all quantum well transitions despite of modification of the quantum well profile.
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Investigation of the non-square InGaAsP/InP quantum wells in the electric field by Photoreflectance
Acta Physica Polonica A, 2002Co-Authors: R Kudrawiec, J Wojcik, B J Robinson, D A Thompson, Grzegorz Sęk, W. Rudno-rudziński, Jan Misiewicz, P MascherAbstract:Non-square quantum wells in electric field have been investigated by Photoreflectance and photoluminescence spectroscopies. The structures have been obtained by a post-growth modification (rapid thermal annealing) of standard 1.55 μm InGaAsP-based laser structures that were grown by gas source molecular beam epitaxy. During rapid thermal annealing a migration of semiconductor atoms across quantum well interfaces changes the quantum well profile from a square well to a rounded well. The modification of the profile changes energy levels in the quantum well and in consequence a blue shift of the quantum well emission peak is observed in photoluminescence. In this paper the blue shift of the ground state transition of post-growth modified quantum well structures has been investigated by both photoluminescence and Photoreflectance techniques. Also a blue shift of excited state transitions has been observed in Photoreflectance spectra. Generally, a stronger blue shift for the ground state transition than for excited state transitions has been observed. Additionally, oscillator strengths for all quantum well transitions have been determined from Photoreflectance spectra. It has been found that the oscillator strength is constant for all quantum well transitions despite of modification of the quantum well profile.
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Photoreflectance investigations of GaN epitaxial layers
Materials Science and Engineering: B, 2001Co-Authors: P. Sitarek, R. Korbutowicz, R Kudrawiec, Grzegorz Sęk, Jan Misiewicz, Regina Paszkiewicz, Bogdan Paszkiewicz, Marek TłaczałaAbstract:Abstract The Photoreflectance spectroscopy was used to investigate GaN epitaxial layers. Heterostructures being under study were grown by metalorganic vapour phase epitaxy (MOVPE) and hydride vapour phase epitaxy (HVPE) techniques on sapphire substrate. All measurements were performed at room temperature, what is an advantage in comparison to other spectroscopic techniques. The Photoreflectance spectra exhibit resonances, which originate from the direct optical transition between the conduction band and valence band. From the energy position of these resonances, the direct band-gap energies of semiconductor being under study were obtained. Franz–Keldysh oscillations (FKO) above the band gap in doped (HVPE) structure are observed. From the period of Franz–Keldysh oscillations the strength of the surface electric field was determined.
T. J. C. Hosea - One of the best experts on this subject based on the ideXlab platform.
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Modelling and analysis of Photoreflectance spectra of GaAs/AlGaAs single-quantum-well structures
Semiconductor Science and Technology, 1995Co-Authors: P J Hughes, T. J. C. Hosea, Bernard L. WeissAbstract:Results are presented for room-temperature Photoreflectance measurements on four GaAs/AlxGa1-xAs single-quantum-well structures, with x=0.2 and x=0.3, and nominal GaAs quantum well widths of 50 AA and 100 AA. However, the Photoreflectance spectra of all the samples display pronounced Franz-Keldysh oscillations in the neighbourhood of both the GaAs and AlxGa1-xAs band edge energies which overlap with, and partially obscure, the Photoreflectance features from the quantum well. The spectra are fitted with a model incorporating an approximate lineshape form for the Franz-Keldysh oscillations together with third-derivative functional forms. This has enabled the single-quantum-well transition energies to be determined as well as the DC electric field responsible for the Franz-Keldysh oscillations. In order to identify these transitions, the results are compared with a theoretical model for the single-quantum-well structures, which incorporates parabolic effective masses, and good agreement is obtained.
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Photoreflectance of single buried Si1−xGex epilayers (0.12
Journal of Applied Physics, 1995Co-Authors: R. T. Carline, T. J. C. Hosea, D. J. HallAbstract:Photoreflectance spectra have been obtained from single strained Si1−xGex epilayers (0.12
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analysis of franz keldysh oscillations in Photoreflectance spectra of a algaas gaas single quantum well structure
Journal of Applied Physics, 1995Co-Authors: P J Hughes, B L Weiss, T. J. C. HoseaAbstract:Experimental results are presented for the physical origins of room‐temperature Photoreflectance features of a AlGaAs/GaAs single‐quantum well structure. The spectra exhibit well‐defined Franz–Keldysh oscillations which overlap with Photoreflectance features due to the quantum well and complicate the determination of the energies of the transitions within the quantum well. The origin of the Franz–Keldysh oscillations are determined using wet chemical etching to selectively remove grown layers down to the substrate. The resulting spectra are presented as a function of etch depth which allows the magnitude of the built‐in electric fields to be determined and reveals the location within the quantum well structure where the Franz–Keldysh oscillations originate.
K. Muratikov - One of the best experts on this subject based on the ideXlab platform.
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Wave optics version of Photoreflectance signal formation in thermal wave experiments with solids
2015Co-Authors: K. MuratikovAbstract:Abstract. A common approach to the determination of the Photoreflectance signal within the framework of wave optics is developed. It is shown that different modes of operation of the thermal wave Photoreflectance microscope are possible. In recent years there has been increasing interest in the development and application of a Photoreflectance thermal wave method. It has been successfully used as a powerful technique for thermal wave imaging and diagnostics of solids, imaging of integrated circuits and se~niconductors [I]. The main advantages of this method are the nondestructive and noncontact type of imaging and the ability to provide high spatial resolution. A further progress in this direction to a great extent is connected with the correct interpretation of the data obtained by the Photoreflectance n~ethod. The influence on the Photoreflectance signal of the sample surface perturbation produced by the optically generated thermal waves is usually investigated within the framework of geometric optics approach [I]. The influence of the sample surface perturbation on the probe beam in this approach is described in terms of deviation in the direction of the reflected probe beam. The effects of influence of thermal and plasma waves on the reflectance coefficient can also be taken into account in this case by means of intensity modulation of the reflected probe beam
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Wave optics version of Photoreflectance signal formation in thermal wave experiments with solids
Journal de Physique IV Colloque, 1994Co-Authors: K. MuratikovAbstract:A common approach to the determination of the Photoreflectance signal within the framework of wave optics is developed. It is shown that different modes of operation of the thermal wave Photoreflectance microscope are possible.
P J Hughes - One of the best experts on this subject based on the ideXlab platform.
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Modelling and analysis of Photoreflectance spectra of GaAs/AlGaAs single-quantum-well structures
Semiconductor Science and Technology, 1995Co-Authors: P J Hughes, T. J. C. Hosea, Bernard L. WeissAbstract:Results are presented for room-temperature Photoreflectance measurements on four GaAs/AlxGa1-xAs single-quantum-well structures, with x=0.2 and x=0.3, and nominal GaAs quantum well widths of 50 AA and 100 AA. However, the Photoreflectance spectra of all the samples display pronounced Franz-Keldysh oscillations in the neighbourhood of both the GaAs and AlxGa1-xAs band edge energies which overlap with, and partially obscure, the Photoreflectance features from the quantum well. The spectra are fitted with a model incorporating an approximate lineshape form for the Franz-Keldysh oscillations together with third-derivative functional forms. This has enabled the single-quantum-well transition energies to be determined as well as the DC electric field responsible for the Franz-Keldysh oscillations. In order to identify these transitions, the results are compared with a theoretical model for the single-quantum-well structures, which incorporates parabolic effective masses, and good agreement is obtained.
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analysis of franz keldysh oscillations in Photoreflectance spectra of a algaas gaas single quantum well structure
Journal of Applied Physics, 1995Co-Authors: P J Hughes, B L Weiss, T. J. C. HoseaAbstract:Experimental results are presented for the physical origins of room‐temperature Photoreflectance features of a AlGaAs/GaAs single‐quantum well structure. The spectra exhibit well‐defined Franz–Keldysh oscillations which overlap with Photoreflectance features due to the quantum well and complicate the determination of the energies of the transitions within the quantum well. The origin of the Franz–Keldysh oscillations are determined using wet chemical etching to selectively remove grown layers down to the substrate. The resulting spectra are presented as a function of etch depth which allows the magnitude of the built‐in electric fields to be determined and reveals the location within the quantum well structure where the Franz–Keldysh oscillations originate.