Amor Bchetnia | University of Monastir (original) (raw)

Papers by Amor Bchetnia

Research paper thumbnail of Study of the partial decomposition of GaN layers grown by MOVPE with different coalescence degree

Journal of Crystal Growth, 2016

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. www.elsevier.com/locate/jcrysgro Study of the partial decomposition of GaN layers grown by MOVPE with different coalescence degree H. Bouazizi (a) , N. Chaaben *(a) , Y. El Gmili (b) , A. Bchetnia (a) , J. P. Salvestrini (c,b) , and B. El Jani (a) .

Research paper thumbnail of Synthesis, characterization, structural analysis and DNA binding studies of nickel(II)–triphenylphosphine complex of ONS donor ligand – Multisubstituted thiosemicarbazone as highly selective sensor for fluoride ion

Polyhedron, 2013

A new kind of Ni(II) complex of the type, [Ni(PPh 3)(L)](1), {where L = chemosensor thiosemicarba... more A new kind of Ni(II) complex of the type, [Ni(PPh 3)(L)](1), {where L = chemosensor thiosemicarbazone = 2-(3-bromo-5-chloro-2-hydroxybenzylidene)-N-phenyhydrazine-carbothioamide} have been synthesized and characterized by NMR, IR, UV-Vis spectroscopic methods and single crystal X-ray studies. Based on spectroscopic and X-ray crystallographic studies, a square planar structure has been proposed for the Ni(II) complex. The interaction between Ni(II) complex and CT-DNA has been investigated using UV-Vis, circular dichroism studies and gel electrophoresis. In UV studies, the observed strong hypochromism in absorption intensities and binding constant value (K b = 1.8 Â 10 5) indicates significant interaction between the electronic states of the Ni(II) complex chromophore with that of DNA bases. With increasing concentration of Ni(II) complex, the peaks at 275 and 245 nm of CT-DNA are shifted to 1-2 nm without any change in the zero-cross over at 259 nm in circular dichroism studies. These observations suggest that the complex bind to DNA through a non-intercalative mode due to the waggling of three phenyl rings of triphenyl phosphine group. The Ni(II) complex display significant hydrolytic cleavage of circular plasmid pUC18 DNA. At high concentration, the Ni(II) complex almost promotes the maximum conversion of DNA from form I to form II along with the appearance of form III. The newly synthesized thiosemicarbazone compound is a promising system for the development of new colorimetric probes for the detection of anions. Anion sensing ability of the receptor (L) with halide ions (F À , Cl À , Br À and I À) have been carried out in different solvents. The receptor shows a remarkable color change from colorless to dark orange in CH 3 CN solution on selective binding with fluoride ion. The anion recognition property of the receptor via hydrogen bonding interactions is monitored by UV-Vis titration and 1 H NMR spectroscopy.

Research paper thumbnail of Two novel pyrazine Zn(II)-porphyrins complexes: Synthesis, photophysical properties, structure study, DFT-Calculation and assessment of an azo dye removal from aqueous solution

Journal of Solid State Chemistry, Mar 1, 2022

Research paper thumbnail of Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE

Superlattices and Microstructures, 2016

Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE J. Laifi (... more Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE J. Laifi (a) , N. Chaaben (a) , H. Bouazizi (a) , N. Fourati (b) , C. Zerrouki (b) , Y. El Gmili (c) , A. Bchetnia (a)* J. P. Salvestrini (c,d) and B. El Jani (a) .

Research paper thumbnail of Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy

Materials Science in Semiconductor Processing, 2015

ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorga... more ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2 x 10(13) to 2 x 10(17) cm(-3). We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Gamma(0) increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.

Research paper thumbnail of Photoluminescence of V-doped GaN thin films grown by MOVPE technique

Microelectronics Journal, 2006

This work reports the photoluminescence (PL) study of vanadium-doped GaN (GaN: V) in the 9-300 K ... more This work reports the photoluminescence (PL) study of vanadium-doped GaN (GaN: V) in the 9-300 K range. Samples have been successfully prepared on sapphire substrates by metalorganic vapour phase epitaxy technique (MOVPE). At room temperature (RT) the PL spectra of GaN: V are dominated by a blue band (BB) in the 2.6 eV range. This BB emission is very strong and its intensity increases with increasing V doping level. We also observed that the peak position of the blue luminescence shifted at lower energy with decreasing excitation density. Upon V-doping, the yellow luminescence band shows a drastic reduction in integrated intensity. This observation is explained by a reaction involving V and gallium vacancy (OGa). PL spectra at low temperature exhibited a series of peaks. The donor-acceptor (D-A) pair emission peak at 3.27 eV was strongly pronounced, as the temperature was decreased. On the other hand, the intensity of the BB emission decreased. This BB emission is due to a radiative transition from a shallow donor with a depth of 29 meV to a deep acceptor with a depth of 832 meV.

Research paper thumbnail of Photoreflectance study of GaN grown on SiN treated sapphire substrate by MOVPE

Superlattices and Microstructures, 2015

ABSTRACT

Research paper thumbnail of Statistical analysis of vanadium in gallium arsenide

physica status solidi (a), 2005

The electrical properties of vanadium-doped GaAs grown by metalorganic vapor phase epitaxy were s... more The electrical properties of vanadium-doped GaAs grown by metalorganic vapor phase epitaxy were studied between 77 and 300 K. The temperature-dependent electron concentration, for different partial pressures of VCl 4 , was simulated using the charge balance equation. A calculation model was used with parameters (energy levels and V concentration) derived from photoluminescence, deep-level transient spectroscopy and secondary ion mass spectroscopy measurements. The magnitude and the temperature dependence of neutral and ionized V concentrations were determined. It is shown that most of the V concentration is inactive. This is in good agreement with some previous reports in the literature. The detailed analysis including the probability of V donor incorporation in GaAs was then extended to explain the evolution of electron concentration as a function of partial pressure of VCl 4 .

Research paper thumbnail of Effects of thermal annealing on n -type GaAs:V grown by MOCVD

Journal of Physics D: Applied Physics, 2006

ABSTRACT Vanadium (V)-doped GaAs (GaAs:V) layers grown by metal–organic chemical vapour depositio... more ABSTRACT Vanadium (V)-doped GaAs (GaAs:V) layers grown by metal–organic chemical vapour deposition under different V-doping levels (1017–1019 cm−3) were annealed in an arsine–H2 gas mixture up to annealing temperatures of 750 and 850 °C for 30 min. The effect of thermal treatments on their electrical and optical properties was studied by means of the Hall effect, deep level transient spectroscopy and photoluminescence (PL). Annealing at 750 °C induces a thermal conversion from the n- to p-type of weakly V-doped GaAs. The conductivity of highly V-doped materials remains n-type. All the V-doped samples convert from n- to p-type following annealing at 850 °C. A comparison between the PL spectra for materials annealed under different conditions underlines the important role of gallium vacancies and a possible V accumulation at the surface in the case of thermal conversion.

Research paper thumbnail of Thermodynamic analysis of growth rate reduction by VCl4 during metalorganic vapor-phase epitaxy of GaAs

Journal of Crystal Growth, 1999

ABSTRACT The growth rate reduction of metalorganic vapor-phase epitaxy (MOVPE) vanadium-doped GaA... more ABSTRACT The growth rate reduction of metalorganic vapor-phase epitaxy (MOVPE) vanadium-doped GaAs layer by vanadium tetrachloride (VCl4) was studied. Laser reflectometry was used to monitor this reduction as a function of the VCl4 flow rate and substrate temperature. A growth rate reduction up to 60% has been observed. The growth rate reduction follows a sublinear variation with the flow rate of VCl4 and exhibits Arrhenius temperature dependence with an activation energy of 1.3eV. Thermodynamic calculations, based on the minimization of the Gibbs energy, have been performed on input system containing arsine, trimethylgallium, hydrogen and vanadium tetrachloride. It is found that the growth rate reduction is essentially due to the GaCl formation in gas and/or solid phase. The thermodynamics equilibrium results are very close to those obtained experimentally.

Research paper thumbnail of Growth of vanadium-doped GaN by MOVPE

Journal of Crystal Growth, 2005

ABSTRACT This paper reports on the vanadium doping of GaN layers grown by metal-organic vapour ph... more ABSTRACT This paper reports on the vanadium doping of GaN layers grown by metal-organic vapour phase epitaxy (MOVPE). We have used vanadium tetrachloride (VCl4) to intentionally incorporate vanadium (V) during crystal growth of GaN. The films were grown on sapphire substrates by in-situ SiN treatment. We describe the in-situ monitoring of the growth process by laser reflectometry. The V incorporation in GaN was investigated by secondary ion mass spectroscopy (SIMS). The V diffusion coefficient in GaN has been calculated to be 10−14cm2s−1 at 1120°C by fitting the V SIMS profile. The high-resolution X-ray diffraction and atomic force microscopy analysis were employed to study the structural and surface morphology of the films. At room temperature, by comparison with un-doped layers grown in the same conditions, photoluminescence spectra of V-doped GaN layers exhibited a strong blue emission band. The intensity of this blue band increases with the increase of VCl4 flow rate. We propose that is associated with intrinsic defects introduced by the growth conditions or V-related intrinsic defects complexes. Upon V-doping, the yellow luminescence band shows a drastic reduction in integrated intensity, which could be due to a decrease in the concentration of gallium vacancy (√Ga) or √Ga-related defect complexes.

Research paper thumbnail of In situ reflectance monitoring of the growth and etching of AlAs/GaAs structures in MOVPE

Journal of Crystal Growth, 2004

We report the in situ optical monitoring of AlAs/GaAs structure elaborated and etched by CCl 4 in... more We report the in situ optical monitoring of AlAs/GaAs structure elaborated and etched by CCl 4 in metalorganic vapour phase epitaxy reactor. We describe the modelling of experimental reflectivity response to determine the properties of AlAs/GaAs structure such as the refractive index and growth/etch rate. Etching rates of AlAs and GaAs increase with the increase of the flow of CCl 4 or the substrate temperature. In most of the cases, the etching rate of GaAs is higher than that of AlAs. This fact might be related to the difference between the chloride species responsible to the mechanism of the etching. The thermodynamic analysis of the two mixtures (solid GaAs+H 2 +CCl 4 and solid AlAs+H 2 +CCl 4) suggests that GaCl and AlCl x (x ¼ 1 À 2) are the species responsible for the etching of GaAs and AlAs by CCl 4 , respectively. The surface flatness of GaAs and AlAs etched by CCl 4 is also qualitatively monitored in situ by laser reflectometry. Specifically, we have studied the evolution surface morphology with etching rate. The smoothest surface is reached by optimizing the etching parameters.

Research paper thumbnail of Etching of GaAs by CCl4 and VCl4 in a metalorganic vapor-phase epitaxy reactor

Journal of Crystal Growth, 1998

In situ etching of GaAs, AlAs and carbon-doped GaAs layers by CCl prior to growth was monitored b... more In situ etching of GaAs, AlAs and carbon-doped GaAs layers by CCl prior to growth was monitored by reflectometry with a 632.8 nm laser beam. A comparison between growth and etching rates of GaAs and carbon-doped GaAs, indicates that the reduction in the growth rate usually observed in heavily carbon-doped GaAs using CCl should be attributed to the Ga reduction by the formation of GaCl V (x"1-3) species in the gas and solid phases. We investigated the etching of the GaAs epitaxial layer or substrate by CCl or VCl gas inside a metalorganic vapor-phase epitaxy (MOVPE) reactor at various temperatures and under different flow rates of CCl or VCl. The evolution of the reflectometry signal gives qualitative informations on the etched surface. A smooth etched surface can be achieved at high temperatures for both tetrachlorides.

Research paper thumbnail of Effect of thickness on structural and electrical properties of GaN films grown on SiN-treated sapphire

Journal of Crystal Growth, 2007

GaN films were grown by metalorganic chemical vapor deposition (MOCVD) on silicon nitride (SiN)-t... more GaN films were grown by metalorganic chemical vapor deposition (MOCVD) on silicon nitride (SiN)-treated c-plane sapphire substrate. Using in situ laser reflectometry, the growth was interrupted at the different stages of the film coalescence. By the help of highresolution X-ray diffraction (HRXRD) and Hall effect measurements, the mosaicity, stress and electrical properties were investigated at all the growth stages. The results showed that tilt and twist mosaic drop with thickness increasing at different rates. During the coalescence process, interaction between tilt and twist mosaic increases and remain almost constant for fully coalesced layers. Hall effect measurements have shown that carrier concentration and mobility have the same sensitivity to the tilt and the twist mosaic. The a and c lattice parameters, as well as the in plane and out-of plane strains were determined. The room temperature compressive stress increases with increasing layer thickness and reaches a maximum level of À0.45 GPa. The effects of SiN treatment on the mosaicity and the stress evolution were discussed from a comparison with the properties of untreated GaN grown layer.

Research paper thumbnail of New vanadium dopant precursor for GaAs growth by metalorganic vapor-phase epitaxy

Journal of Crystal Growth, 1998

Vanadium-doped GaAs was grown by metalorganic vapor-phase epitaxy (MOVPE) using vanadium (IV) chl... more Vanadium-doped GaAs was grown by metalorganic vapor-phase epitaxy (MOVPE) using vanadium (IV) chloride VCl as a novel dopant source. The optimum growth conditions were achieved using reflectometry with a 632.8 nm laser beam. A reduction in the growth rate of V-doped GaAs was observed and attributed to the etching by Cl species associated to the use of high flow of VCl. The incorporation of vanadium in GaAs was investigated by secondary ion mass spectroscopy (SIMS) measurements. Samples were also characterized by room temperature Hall effect. Electron concentrations ranging from 10 to 2;10 cm\ have been obtained. The maximum resistivity is about 715 cm. For all samples high compensation ratio larger than 0.7 was observed. The comparison between only silicon-doped GaAs and silicon-vanadium Co-doped GaAs, showed that there was no effect in modifying the compensation ratio. 1998 Elsevier Science B.V. All rights reserved.

Research paper thumbnail of New photoluminescence lines in Vanadium doped GaAs grown by MOVPE

Microelectronics Journal, 2003

We examined the electrical and optical properties of vanadium-doped GaAs grown by metalorganic va... more We examined the electrical and optical properties of vanadium-doped GaAs grown by metalorganic vapour phase epitaxy using vanadium tetrachloride (VCl4) as a novel dopant source. Samples with various vanadium incorporations were investigated. All samples were n type. The electron concentration dependence on the VCl4 flow rate was established. At 15K, by comparison with undoped layers grown in the same conditions,

Research paper thumbnail of Mosaicity and stress effects on luminescence properties of GaN

physica status solidi (a), 2008

ABSTRACT High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c ... more ABSTRACT High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c -plane sapphire substrate by metal-organic chemical vapour phase deposition (MOCVD) were investigated. Photoluminescence (PL) measurements were carried out at 13 K. GaN mosaicity was studied at different growth stage with a thickness varying from 0.1 to 4.5 µm. Rocking curves of symmetric and asymmetric plane reflections were investigated to determine respectively the tilt and twist mosaic. Using PL spectra and HRXRD scattering a correlation were found between the intensity and the full width at half maximum (FWHM) of the bound exciton neutral donor (I2) with the GaN mosaicity. The I2 intensity increased significantly with increasing the interaction parameter (m) between tilt and twist mosaic, whereas the FWHM of I2 decreased with increasing m. The evolution of the compressive stress with thickness is extracted from HRXRD and correlated with PL measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Research paper thumbnail of Mosaicity and stress effects on luminescence properties of GaN

Physica Status Solidi (A) Applications and Materials

High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c -plane sa... more High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c -plane sapphire substrate by metal-organic chemical vapour phase deposition (MOCVD) were investigated. Photoluminescence (PL) measurements were carried out at 13 K. GaN mosaicity was studied at different growth stage with a thickness varying from 0.1 to 4.5 µm. Rocking curves of symmetric and asymmetric plane reflections were investigated to determine respectively the tilt and twist mosaic. Using PL spectra and HRXRD scattering a correlation were found between the intensity and the full width at half maximum (FWHM) of the bound exciton neutral donor (I2) with the GaN mosaicity. The I2 intensity increased significantly with increasing the interaction parameter (m) between tilt and twist mosaic, whereas the FWHM of I2 decreased with increasing m. The evolution of the compressive stress with thickness is extracted from HRXRD and correlated with PL measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KG...

Research paper thumbnail of Structural, Morphological, Optical and Electrical Properties of Zn<sub>(1-x)</sub>Cd<sub>x</sub>O Solid Solution Grown on <i>a</i>- and <i>r</i>-Plane Sapphire Substrate by MOCV

Journal of Crystallization Process and Technology, 2013

Research paper thumbnail of Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy

Materials Science in Semiconductor Processing, 2015

ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorga... more ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2 x 10(13) to 2 x 10(17) cm(-3). We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Gamma(0) increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.

Research paper thumbnail of Study of the partial decomposition of GaN layers grown by MOVPE with different coalescence degree

Journal of Crystal Growth, 2016

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. www.elsevier.com/locate/jcrysgro Study of the partial decomposition of GaN layers grown by MOVPE with different coalescence degree H. Bouazizi (a) , N. Chaaben *(a) , Y. El Gmili (b) , A. Bchetnia (a) , J. P. Salvestrini (c,b) , and B. El Jani (a) .

Research paper thumbnail of Synthesis, characterization, structural analysis and DNA binding studies of nickel(II)–triphenylphosphine complex of ONS donor ligand – Multisubstituted thiosemicarbazone as highly selective sensor for fluoride ion

Polyhedron, 2013

A new kind of Ni(II) complex of the type, [Ni(PPh 3)(L)](1), {where L = chemosensor thiosemicarba... more A new kind of Ni(II) complex of the type, [Ni(PPh 3)(L)](1), {where L = chemosensor thiosemicarbazone = 2-(3-bromo-5-chloro-2-hydroxybenzylidene)-N-phenyhydrazine-carbothioamide} have been synthesized and characterized by NMR, IR, UV-Vis spectroscopic methods and single crystal X-ray studies. Based on spectroscopic and X-ray crystallographic studies, a square planar structure has been proposed for the Ni(II) complex. The interaction between Ni(II) complex and CT-DNA has been investigated using UV-Vis, circular dichroism studies and gel electrophoresis. In UV studies, the observed strong hypochromism in absorption intensities and binding constant value (K b = 1.8 Â 10 5) indicates significant interaction between the electronic states of the Ni(II) complex chromophore with that of DNA bases. With increasing concentration of Ni(II) complex, the peaks at 275 and 245 nm of CT-DNA are shifted to 1-2 nm without any change in the zero-cross over at 259 nm in circular dichroism studies. These observations suggest that the complex bind to DNA through a non-intercalative mode due to the waggling of three phenyl rings of triphenyl phosphine group. The Ni(II) complex display significant hydrolytic cleavage of circular plasmid pUC18 DNA. At high concentration, the Ni(II) complex almost promotes the maximum conversion of DNA from form I to form II along with the appearance of form III. The newly synthesized thiosemicarbazone compound is a promising system for the development of new colorimetric probes for the detection of anions. Anion sensing ability of the receptor (L) with halide ions (F À , Cl À , Br À and I À) have been carried out in different solvents. The receptor shows a remarkable color change from colorless to dark orange in CH 3 CN solution on selective binding with fluoride ion. The anion recognition property of the receptor via hydrogen bonding interactions is monitored by UV-Vis titration and 1 H NMR spectroscopy.

Research paper thumbnail of Two novel pyrazine Zn(II)-porphyrins complexes: Synthesis, photophysical properties, structure study, DFT-Calculation and assessment of an azo dye removal from aqueous solution

Journal of Solid State Chemistry, Mar 1, 2022

Research paper thumbnail of Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE

Superlattices and Microstructures, 2016

Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE J. Laifi (... more Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE J. Laifi (a) , N. Chaaben (a) , H. Bouazizi (a) , N. Fourati (b) , C. Zerrouki (b) , Y. El Gmili (c) , A. Bchetnia (a)* J. P. Salvestrini (c,d) and B. El Jani (a) .

Research paper thumbnail of Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy

Materials Science in Semiconductor Processing, 2015

ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorga... more ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2 x 10(13) to 2 x 10(17) cm(-3). We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Gamma(0) increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.

Research paper thumbnail of Photoluminescence of V-doped GaN thin films grown by MOVPE technique

Microelectronics Journal, 2006

This work reports the photoluminescence (PL) study of vanadium-doped GaN (GaN: V) in the 9-300 K ... more This work reports the photoluminescence (PL) study of vanadium-doped GaN (GaN: V) in the 9-300 K range. Samples have been successfully prepared on sapphire substrates by metalorganic vapour phase epitaxy technique (MOVPE). At room temperature (RT) the PL spectra of GaN: V are dominated by a blue band (BB) in the 2.6 eV range. This BB emission is very strong and its intensity increases with increasing V doping level. We also observed that the peak position of the blue luminescence shifted at lower energy with decreasing excitation density. Upon V-doping, the yellow luminescence band shows a drastic reduction in integrated intensity. This observation is explained by a reaction involving V and gallium vacancy (OGa). PL spectra at low temperature exhibited a series of peaks. The donor-acceptor (D-A) pair emission peak at 3.27 eV was strongly pronounced, as the temperature was decreased. On the other hand, the intensity of the BB emission decreased. This BB emission is due to a radiative transition from a shallow donor with a depth of 29 meV to a deep acceptor with a depth of 832 meV.

Research paper thumbnail of Photoreflectance study of GaN grown on SiN treated sapphire substrate by MOVPE

Superlattices and Microstructures, 2015

ABSTRACT

Research paper thumbnail of Statistical analysis of vanadium in gallium arsenide

physica status solidi (a), 2005

The electrical properties of vanadium-doped GaAs grown by metalorganic vapor phase epitaxy were s... more The electrical properties of vanadium-doped GaAs grown by metalorganic vapor phase epitaxy were studied between 77 and 300 K. The temperature-dependent electron concentration, for different partial pressures of VCl 4 , was simulated using the charge balance equation. A calculation model was used with parameters (energy levels and V concentration) derived from photoluminescence, deep-level transient spectroscopy and secondary ion mass spectroscopy measurements. The magnitude and the temperature dependence of neutral and ionized V concentrations were determined. It is shown that most of the V concentration is inactive. This is in good agreement with some previous reports in the literature. The detailed analysis including the probability of V donor incorporation in GaAs was then extended to explain the evolution of electron concentration as a function of partial pressure of VCl 4 .

Research paper thumbnail of Effects of thermal annealing on n -type GaAs:V grown by MOCVD

Journal of Physics D: Applied Physics, 2006

ABSTRACT Vanadium (V)-doped GaAs (GaAs:V) layers grown by metal–organic chemical vapour depositio... more ABSTRACT Vanadium (V)-doped GaAs (GaAs:V) layers grown by metal–organic chemical vapour deposition under different V-doping levels (1017–1019 cm−3) were annealed in an arsine–H2 gas mixture up to annealing temperatures of 750 and 850 °C for 30 min. The effect of thermal treatments on their electrical and optical properties was studied by means of the Hall effect, deep level transient spectroscopy and photoluminescence (PL). Annealing at 750 °C induces a thermal conversion from the n- to p-type of weakly V-doped GaAs. The conductivity of highly V-doped materials remains n-type. All the V-doped samples convert from n- to p-type following annealing at 850 °C. A comparison between the PL spectra for materials annealed under different conditions underlines the important role of gallium vacancies and a possible V accumulation at the surface in the case of thermal conversion.

Research paper thumbnail of Thermodynamic analysis of growth rate reduction by VCl4 during metalorganic vapor-phase epitaxy of GaAs

Journal of Crystal Growth, 1999

ABSTRACT The growth rate reduction of metalorganic vapor-phase epitaxy (MOVPE) vanadium-doped GaA... more ABSTRACT The growth rate reduction of metalorganic vapor-phase epitaxy (MOVPE) vanadium-doped GaAs layer by vanadium tetrachloride (VCl4) was studied. Laser reflectometry was used to monitor this reduction as a function of the VCl4 flow rate and substrate temperature. A growth rate reduction up to 60% has been observed. The growth rate reduction follows a sublinear variation with the flow rate of VCl4 and exhibits Arrhenius temperature dependence with an activation energy of 1.3eV. Thermodynamic calculations, based on the minimization of the Gibbs energy, have been performed on input system containing arsine, trimethylgallium, hydrogen and vanadium tetrachloride. It is found that the growth rate reduction is essentially due to the GaCl formation in gas and/or solid phase. The thermodynamics equilibrium results are very close to those obtained experimentally.

Research paper thumbnail of Growth of vanadium-doped GaN by MOVPE

Journal of Crystal Growth, 2005

ABSTRACT This paper reports on the vanadium doping of GaN layers grown by metal-organic vapour ph... more ABSTRACT This paper reports on the vanadium doping of GaN layers grown by metal-organic vapour phase epitaxy (MOVPE). We have used vanadium tetrachloride (VCl4) to intentionally incorporate vanadium (V) during crystal growth of GaN. The films were grown on sapphire substrates by in-situ SiN treatment. We describe the in-situ monitoring of the growth process by laser reflectometry. The V incorporation in GaN was investigated by secondary ion mass spectroscopy (SIMS). The V diffusion coefficient in GaN has been calculated to be 10−14cm2s−1 at 1120°C by fitting the V SIMS profile. The high-resolution X-ray diffraction and atomic force microscopy analysis were employed to study the structural and surface morphology of the films. At room temperature, by comparison with un-doped layers grown in the same conditions, photoluminescence spectra of V-doped GaN layers exhibited a strong blue emission band. The intensity of this blue band increases with the increase of VCl4 flow rate. We propose that is associated with intrinsic defects introduced by the growth conditions or V-related intrinsic defects complexes. Upon V-doping, the yellow luminescence band shows a drastic reduction in integrated intensity, which could be due to a decrease in the concentration of gallium vacancy (√Ga) or √Ga-related defect complexes.

Research paper thumbnail of In situ reflectance monitoring of the growth and etching of AlAs/GaAs structures in MOVPE

Journal of Crystal Growth, 2004

We report the in situ optical monitoring of AlAs/GaAs structure elaborated and etched by CCl 4 in... more We report the in situ optical monitoring of AlAs/GaAs structure elaborated and etched by CCl 4 in metalorganic vapour phase epitaxy reactor. We describe the modelling of experimental reflectivity response to determine the properties of AlAs/GaAs structure such as the refractive index and growth/etch rate. Etching rates of AlAs and GaAs increase with the increase of the flow of CCl 4 or the substrate temperature. In most of the cases, the etching rate of GaAs is higher than that of AlAs. This fact might be related to the difference between the chloride species responsible to the mechanism of the etching. The thermodynamic analysis of the two mixtures (solid GaAs+H 2 +CCl 4 and solid AlAs+H 2 +CCl 4) suggests that GaCl and AlCl x (x ¼ 1 À 2) are the species responsible for the etching of GaAs and AlAs by CCl 4 , respectively. The surface flatness of GaAs and AlAs etched by CCl 4 is also qualitatively monitored in situ by laser reflectometry. Specifically, we have studied the evolution surface morphology with etching rate. The smoothest surface is reached by optimizing the etching parameters.

Research paper thumbnail of Etching of GaAs by CCl4 and VCl4 in a metalorganic vapor-phase epitaxy reactor

Journal of Crystal Growth, 1998

In situ etching of GaAs, AlAs and carbon-doped GaAs layers by CCl prior to growth was monitored b... more In situ etching of GaAs, AlAs and carbon-doped GaAs layers by CCl prior to growth was monitored by reflectometry with a 632.8 nm laser beam. A comparison between growth and etching rates of GaAs and carbon-doped GaAs, indicates that the reduction in the growth rate usually observed in heavily carbon-doped GaAs using CCl should be attributed to the Ga reduction by the formation of GaCl V (x"1-3) species in the gas and solid phases. We investigated the etching of the GaAs epitaxial layer or substrate by CCl or VCl gas inside a metalorganic vapor-phase epitaxy (MOVPE) reactor at various temperatures and under different flow rates of CCl or VCl. The evolution of the reflectometry signal gives qualitative informations on the etched surface. A smooth etched surface can be achieved at high temperatures for both tetrachlorides.

Research paper thumbnail of Effect of thickness on structural and electrical properties of GaN films grown on SiN-treated sapphire

Journal of Crystal Growth, 2007

GaN films were grown by metalorganic chemical vapor deposition (MOCVD) on silicon nitride (SiN)-t... more GaN films were grown by metalorganic chemical vapor deposition (MOCVD) on silicon nitride (SiN)-treated c-plane sapphire substrate. Using in situ laser reflectometry, the growth was interrupted at the different stages of the film coalescence. By the help of highresolution X-ray diffraction (HRXRD) and Hall effect measurements, the mosaicity, stress and electrical properties were investigated at all the growth stages. The results showed that tilt and twist mosaic drop with thickness increasing at different rates. During the coalescence process, interaction between tilt and twist mosaic increases and remain almost constant for fully coalesced layers. Hall effect measurements have shown that carrier concentration and mobility have the same sensitivity to the tilt and the twist mosaic. The a and c lattice parameters, as well as the in plane and out-of plane strains were determined. The room temperature compressive stress increases with increasing layer thickness and reaches a maximum level of À0.45 GPa. The effects of SiN treatment on the mosaicity and the stress evolution were discussed from a comparison with the properties of untreated GaN grown layer.

Research paper thumbnail of New vanadium dopant precursor for GaAs growth by metalorganic vapor-phase epitaxy

Journal of Crystal Growth, 1998

Vanadium-doped GaAs was grown by metalorganic vapor-phase epitaxy (MOVPE) using vanadium (IV) chl... more Vanadium-doped GaAs was grown by metalorganic vapor-phase epitaxy (MOVPE) using vanadium (IV) chloride VCl as a novel dopant source. The optimum growth conditions were achieved using reflectometry with a 632.8 nm laser beam. A reduction in the growth rate of V-doped GaAs was observed and attributed to the etching by Cl species associated to the use of high flow of VCl. The incorporation of vanadium in GaAs was investigated by secondary ion mass spectroscopy (SIMS) measurements. Samples were also characterized by room temperature Hall effect. Electron concentrations ranging from 10 to 2;10 cm\ have been obtained. The maximum resistivity is about 715 cm. For all samples high compensation ratio larger than 0.7 was observed. The comparison between only silicon-doped GaAs and silicon-vanadium Co-doped GaAs, showed that there was no effect in modifying the compensation ratio. 1998 Elsevier Science B.V. All rights reserved.

Research paper thumbnail of New photoluminescence lines in Vanadium doped GaAs grown by MOVPE

Microelectronics Journal, 2003

We examined the electrical and optical properties of vanadium-doped GaAs grown by metalorganic va... more We examined the electrical and optical properties of vanadium-doped GaAs grown by metalorganic vapour phase epitaxy using vanadium tetrachloride (VCl4) as a novel dopant source. Samples with various vanadium incorporations were investigated. All samples were n type. The electron concentration dependence on the VCl4 flow rate was established. At 15K, by comparison with undoped layers grown in the same conditions,

Research paper thumbnail of Mosaicity and stress effects on luminescence properties of GaN

physica status solidi (a), 2008

ABSTRACT High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c ... more ABSTRACT High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c -plane sapphire substrate by metal-organic chemical vapour phase deposition (MOCVD) were investigated. Photoluminescence (PL) measurements were carried out at 13 K. GaN mosaicity was studied at different growth stage with a thickness varying from 0.1 to 4.5 µm. Rocking curves of symmetric and asymmetric plane reflections were investigated to determine respectively the tilt and twist mosaic. Using PL spectra and HRXRD scattering a correlation were found between the intensity and the full width at half maximum (FWHM) of the bound exciton neutral donor (I2) with the GaN mosaicity. The I2 intensity increased significantly with increasing the interaction parameter (m) between tilt and twist mosaic, whereas the FWHM of I2 decreased with increasing m. The evolution of the compressive stress with thickness is extracted from HRXRD and correlated with PL measurements. (© 2008 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Research paper thumbnail of Mosaicity and stress effects on luminescence properties of GaN

Physica Status Solidi (A) Applications and Materials

High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c -plane sa... more High-resolution X-ray diffraction (HRXRD) of several GaN layers grown on Si/N treated c -plane sapphire substrate by metal-organic chemical vapour phase deposition (MOCVD) were investigated. Photoluminescence (PL) measurements were carried out at 13 K. GaN mosaicity was studied at different growth stage with a thickness varying from 0.1 to 4.5 µm. Rocking curves of symmetric and asymmetric plane reflections were investigated to determine respectively the tilt and twist mosaic. Using PL spectra and HRXRD scattering a correlation were found between the intensity and the full width at half maximum (FWHM) of the bound exciton neutral donor (I2) with the GaN mosaicity. The I2 intensity increased significantly with increasing the interaction parameter (m) between tilt and twist mosaic, whereas the FWHM of I2 decreased with increasing m. The evolution of the compressive stress with thickness is extracted from HRXRD and correlated with PL measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KG...

Research paper thumbnail of Structural, Morphological, Optical and Electrical Properties of Zn<sub>(1-x)</sub>Cd<sub>x</sub>O Solid Solution Grown on <i>a</i>- and <i>r</i>-Plane Sapphire Substrate by MOCV

Journal of Crystallization Process and Technology, 2013

Research paper thumbnail of Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy

Materials Science in Semiconductor Processing, 2015

ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorga... more ABSTRACT We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2 x 10(13) to 2 x 10(17) cm(-3). We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Gamma(0) increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.