PEDRO HIDALGO ALCALDE - Academia.edu (original) (raw)
Papers by PEDRO HIDALGO ALCALDE
Solid State Phenomena, Dec 1, 1998
Crystal Growth & Design, 2019
Herein, we report the formation of a particular core-shell structure, with a zinc germanate (Zn 2... more Herein, we report the formation of a particular core-shell structure, with a zinc germanate (Zn 2 GeO 4) nanowire core and a discontinuous shell of SnO 2 nanocrystals, obtained in a single step process. We propose a growth model that combines the Plateau-Rayleigh mechanism to produce a pattern of amorphous germanium oxide (a-GeO 2) particles along the Zn 2 GeO 4 nanowire, and the subsequent growth of well-faceted SnO 2 crystals when the nanowire orientation meets good lattice matching conditions. In this latter case, the linear array of a-GeO 2 particles acts as nucleation sites for the SnO 2 crystallites leading to a skewer-like morphology that retains the periodicity of the Plateau-Rayleigh process. Otherwise, nanowires with different orientations appear decorated with a pattern of a-GeO 2 beads mimicking a necklace. Atomic resolution electron microscopy has been used to characterize the Zn 2 GeO 4 /SnO 2 nanoheterostructures. Besides, optical confinement effects have been observed in the luminescence maps and spectra, which have potential for further exploitation in the design of optical microcavities.
MRS Proceedings, 1998
Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to investigate t... more Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to investigate the effect of doping with an isoelectronic dopant, aluminum, on the native acceptors and on the general structure of extended defects of gallium antimonide single crystals. While there is no significant change in the native defect content, decoration of non-radiative recombination centers or extended defects occurs as a result of aluminum doping.
Applied Physics Letters, 2014
Materials Science and Engineering: B, 2000
In this work several changes induced by polishing, chemical etching and thermal treatment in the ... more In this work several changes induced by polishing, chemical etching and thermal treatment in the properties of Er-and Nd-doped GaSb substrates with different doping levels grown by the vertical Bridgman method have been studied. The analysis has revealed the formation of precipitates at the highest doping levels for both Er-and Nd-doped GaSb. Cathodoluminescence analysis shows the reduction of the defect band induced by the rare earth (RE) elements. For high dopant concentrations the precipitation phenomena reduce this effect. Thermal treatments have produced an enhancement of the p-type properties of the samples. For a dopant density of 2×10 19 cm − 3 this effect is more pronounced.
CrystEngComm, 2010
Bulk CZT crystals doped with Bi (1 Â 10 19 at/cm 3) have been grown by the Oscillatory Bridgman m... more Bulk CZT crystals doped with Bi (1 Â 10 19 at/cm 3) have been grown by the Oscillatory Bridgman method, the growth velocity and the zinc concentration profile being improved by the insertion of a Pt tube acting as a cold finger. The stoichiometric uniformity was examined by energy dispersive X-ray analysis, and the zinc concentration was confirmed by inductively coupled plasma mass spectroscopy and cathodoluminescence measurements. The resistivity value was in the range of 8 Â 10 8 U cm, being smaller for the passivated sample, which at the same time had counter device properties.
The interest of rare earth doping of semiconductors has increased in the last years due to its po... more The interest of rare earth doping of semiconductors has increased in the last years due to its possible applications in optical devices requiring temperature stability. Advantages of these systems are the presence of a sharp temperature independent rare-earth luminescence and the possibility of activation of the emitting rare-earth centers by minority carrier injection. In this work the effect of erbium doping on the luminescence and on the native accepters of GaSb crystals has been investigated by CL-SEM. Er doping has been found to increase the total CL intensity and to produce spectral changes that depend on the erbium concentration. At moderate doping the native acceptor concentration, as detected by the luminescence band A, decreases. At high Er concentrations Er-Sb precipitates form and doping appears not to be efficient in the suppression of accepters. X-ray microanalysis reveals that the composition of the precipitates is Er-5 Sb-3. Emission from intraionic transitions of Er...
Acta Materialia, 2020
Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devic... more Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devices. Herein, we investigate the UV luminescence of zinc germanate Zn 2 GeO 4 microwires by means of photoluminescence measurements as a function of temperature and excitation conditions. The emitted UV light is composed of two bands (a broad one and a narrow one) associated with the native defects structure. In addition, with the aid of density functional theory (DFT) calculations, the energy positions of the electronic levels related to native defects in Zn 2 GeO 4 have been calculated. In particular, our results support that zinc interstitials are the responsible for the narrow UV band, which is, in turn, split into two components with different temperature dependence 1 arXiv:2007.15336v1 [cond-mat.mtrl-sci] 30 Jul 2020 behaviour. The origin of the two components is explained on the basis of the particular location of Zn i in the lattice and agrees with DFT calculations. Furthermore, a kinetic luminescence model is proposed to ascertain the temperature evolution of this UV emission. These results pave the way to exploit defect engineering in achieving functional optoelectronic devices to operate in the UV region.
RSC Advances, 2020
The growth mechanism of layered α-MoO3 nano- and microplates on the surface of Mo wires during Jo... more The growth mechanism of layered α-MoO3 nano- and microplates on the surface of Mo wires during Joule heating has been investigated by application of an external electric field to the current carrying wire.
Scientific Reports, 2019
We report on a novel implementation of the cryo-etching method, which enabled us to fabricate low... more We report on a novel implementation of the cryo-etching method, which enabled us to fabricate low-roughness hBN-encapsulated graphene nanoconstrictions with unprecedented control of the structure edges; the typical edge roughness is on the order of a few nanometers. We characterized the system by atomic force microscopy and used the measured parameters of the edge geometry in numerical simulations of the system conductance, which agree quantitatively with our low temperature transport measurements. The quality of our devices is confirmed by the observation of well defined quantized 2e2/h conductance steps at zero magnetic field. To the best of our knowledge, such an observation reports the clearest conductance quantization in physically etched graphene nanoconstrictions. The fabrication of such high quality systems and the scalability of the cryo-etching method opens a novel promising possibility of producing more complex truly-ballistic devices based on graphene.
Solid State Communications, 1998
The effect of aluminium on the defect structure of GaSb crystals, grown by the vertical Bridgman ... more The effect of aluminium on the defect structure of GaSb crystals, grown by the vertical Bridgman technique, has been investigated by cathodoluminescence (CL) in the scanning electron microscope. Crystals have been found to be highly homogeneous along the growth axis with the exception of the top end which showed Al accumulation. The CL results show decoration of extended defects by Al but contrary to the case of other dopants Al has not been found to cause a significative reduction of native acceptors. A CL band at about 850 meV appears to be related to the presence of aluminium.
Semiconductor Science and Technology, 1998
GaSb single crystals with different Er concentrations have been studied by cathodoluminescence in... more GaSb single crystals with different Er concentrations have been studied by cathodoluminescence in the scanning electron microscope. Low Er doping has been found to reduce the concentration of native acceptors. In crystals with higher Er concentrations, Er-Sb precipitates form and doping becomes less efficient in suppressing the acceptors. In these samples intraionic Er luminescence is observed.
physica status solidi (c), 2005
This paper presents cathodoluminescence, electrical and structural characteristics of (11-20)-ori... more This paper presents cathodoluminescence, electrical and structural characteristics of (11-20)-oriented 4H-SiC substrates, aiming at determining properties of some extended defects. As-grown basal plane dislocations with the Burgers vector b = 1/3 <11-20> previously revealed to be associated to a radiative recombination level at 1.80 eV. Well controlled dislocations were here introduced by annealing the sample under compressive stress at 973 K. After the annealing, double stacking faults were detected, formed by two Shockley partial dislocations gliding in two successive basal planes. These defects proved to introduce a rectifying behaviour during forward voltage operation, with a corresponding barrier height value of 0.58 eV at room temperature. Cathodoluminescence measurements allowed to attribute a radiative level at 1.80 eV to the extended defects, giving rise to a double luminescence peak.
Materials Science and Engineering: B, 2001
In this work pure and Gd-doped GaSb ingots with different dopant concentrations were grown by the... more In this work pure and Gd-doped GaSb ingots with different dopant concentrations were grown by the Bridgman Method. The compositional and electrical analysis carried out on these materials have shown the dependence of these results on the initial dopant concentration. The analysis have revealed the presence of inclusions which have been identified as Gd-Sb precipitates. The doped material was found to be p-type with a maximum value of the carrier density at the central region of the ingots. It has been also demonstrated that the Gd enhances the A band emission reducing the band-gap emission.
Materials Science and Engineering: B, 2001
We report here the studies carried out in zinc diffused n-type GaSb by cathodoluminescence (CL) m... more We report here the studies carried out in zinc diffused n-type GaSb by cathodoluminescence (CL) microscopy and by scanning tunneling spectroscopy. Samples with different diffusion profiles measured by secondary ion mass spectrometry (SIMS) were obtained. CL plan-view observations show high homogeneity in the diffused layers. Cross-sectional measurements of the Zn diffused layers were performed by current imaging tunneling spectroscopy (CITS). The junction border was revealed clearly in the CITS images and conductance spectra recorded at differents points of the layers provided information on the local surface band gaps and the conductive behaviour. The results were related to the diffusion profiles and were found to agree with diffusion models suggested previously.
Materials Science and Engineering: A, 2010
The microstructure and mechanical properties in the interface region of a multilayer composite la... more The microstructure and mechanical properties in the interface region of a multilayer composite laminate based on Al-Zn (Al 7075) and Al-Cu (Al 2024) alloys have been mainly characterized by EBSD and shear tests. It is shown that varying solution heat treatments affect the microstructure of the constituent aluminium alloys in the bonding region and, as a consequence, the interfacial mechanical properties. The increase in the solution treatment time improves the interfacial toughness of the multilayer aluminium laminate due to higher intrinsic toughness of the constituent aluminium alloys.
Journal of Crystal Growth, 2002
Nd-doped GaSb bulk crystals with three different dopant concentrations have been grown by the ver... more Nd-doped GaSb bulk crystals with three different dopant concentrations have been grown by the vertical Bridgman technique. The axial segregation has been characterised by obtaining the effective segregation coefficient. Differences in the value of this coefficient show its dopant concentration dependence. Resistivity, carrier density and mobility have also been obtained showing the p-type nature of this material. Structural and compositional properties have been studied revealing some inclusions with high Nd concentration in the highest Nd-doped ingot.
Journal of Crystal Growth, 2008
Cadmium telluride (CdTe) crystals and epitaxial layers were grown by the vertical Bridgman method... more Cadmium telluride (CdTe) crystals and epitaxial layers were grown by the vertical Bridgman method and vapor-phase epitaxy, respectively, to obtain the high-resistive material suitable for X-and gamma-ray detectors. The crystals and layers were doped with Ge at the concentration of 5 Â 10 17 cm À3 and co-doped with the rare element Yb at the concentration range from 1 Â 10 17 to 1 Â 10 19 cm À3. The CdTe:Ge:Yb samples were studied by the structural and electrical characterization techniques, low-temperature photoluminescence (PL) and cathodoluminescence (CL) spectroscopy and CL imaging. Experimental findings testify that homogeneous crystals and layers of reasonably good structural quality can be grown with the Yb concentration below the value of 5 Â 10 18 cm À3 that is estimated to be the limit for Yb solubility in CdTe:Ge:Yb. These findings seem to be related with the purification effect caused by the interaction of the Yb dopant with the group I residual impurities.
Journal of Applied Physics, 2010
The II-VI compound semiconductor cadmium zinc telluride ͑CZT͒ is very useful for room temperature... more The II-VI compound semiconductor cadmium zinc telluride ͑CZT͒ is very useful for room temperature radiation detection applications. In the present research, we have successfully grown Bi doped CZT single crystals with two different zinc concentrations ͑8 and 14 at. %͒ by the Bridgman oscillation method, in which one experiment has been carried out with a platinum ͑Pt͒ tube as the ampoule support. Pt also acts as a cold finger and reduces the growth velocity and enhances crystalline perfection. The grown single crystals have been studied with different analysis methods. The stoichiometry was confirmed by energy dispersive by x-ray and inductively coupled plasma mass spectroscopy analyses and it was found there is no incorporation of impurities in the grown crystal. The presence of Cd and Te vacancies was determined by cathodoluminescence studies. Electrical properties were assessed by I-V analysis and indicated higher resistive value ͑8.53 ϫ 10 8 ⍀ cm͒ for the crystal grown with higher zinc concentration ͑with Cd excess͒ compare to the other ͑3.71ϫ 10 5 ⍀ cm͒.
The European Physical Journal Applied Physics, 2004
Silicon Carbide (SiC) is a wide band gap semiconductor, having opto-electronic properties that ar... more Silicon Carbide (SiC) is a wide band gap semiconductor, having opto-electronic properties that are suitable for many applications. Some structural defects due to crystal growth and/or doping technologies are commonly present in the substrates of SiC. The (1120)-oriented 4H-SiC bulk wafers are particularly investigated, due to some advantages with respect to the (0001)-Si face. One of these advantages is a better crystal reordering during post-implantation annealing. In this paper cathodoluminescence (CL) and X-Ray topography measurements have been carried out in order to investigate the optical and structural properties of commercial (1120) 4H n +-type substrates.
Solid State Phenomena, Dec 1, 1998
Crystal Growth & Design, 2019
Herein, we report the formation of a particular core-shell structure, with a zinc germanate (Zn 2... more Herein, we report the formation of a particular core-shell structure, with a zinc germanate (Zn 2 GeO 4) nanowire core and a discontinuous shell of SnO 2 nanocrystals, obtained in a single step process. We propose a growth model that combines the Plateau-Rayleigh mechanism to produce a pattern of amorphous germanium oxide (a-GeO 2) particles along the Zn 2 GeO 4 nanowire, and the subsequent growth of well-faceted SnO 2 crystals when the nanowire orientation meets good lattice matching conditions. In this latter case, the linear array of a-GeO 2 particles acts as nucleation sites for the SnO 2 crystallites leading to a skewer-like morphology that retains the periodicity of the Plateau-Rayleigh process. Otherwise, nanowires with different orientations appear decorated with a pattern of a-GeO 2 beads mimicking a necklace. Atomic resolution electron microscopy has been used to characterize the Zn 2 GeO 4 /SnO 2 nanoheterostructures. Besides, optical confinement effects have been observed in the luminescence maps and spectra, which have potential for further exploitation in the design of optical microcavities.
MRS Proceedings, 1998
Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to investigate t... more Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to investigate the effect of doping with an isoelectronic dopant, aluminum, on the native acceptors and on the general structure of extended defects of gallium antimonide single crystals. While there is no significant change in the native defect content, decoration of non-radiative recombination centers or extended defects occurs as a result of aluminum doping.
Applied Physics Letters, 2014
Materials Science and Engineering: B, 2000
In this work several changes induced by polishing, chemical etching and thermal treatment in the ... more In this work several changes induced by polishing, chemical etching and thermal treatment in the properties of Er-and Nd-doped GaSb substrates with different doping levels grown by the vertical Bridgman method have been studied. The analysis has revealed the formation of precipitates at the highest doping levels for both Er-and Nd-doped GaSb. Cathodoluminescence analysis shows the reduction of the defect band induced by the rare earth (RE) elements. For high dopant concentrations the precipitation phenomena reduce this effect. Thermal treatments have produced an enhancement of the p-type properties of the samples. For a dopant density of 2×10 19 cm − 3 this effect is more pronounced.
CrystEngComm, 2010
Bulk CZT crystals doped with Bi (1 Â 10 19 at/cm 3) have been grown by the Oscillatory Bridgman m... more Bulk CZT crystals doped with Bi (1 Â 10 19 at/cm 3) have been grown by the Oscillatory Bridgman method, the growth velocity and the zinc concentration profile being improved by the insertion of a Pt tube acting as a cold finger. The stoichiometric uniformity was examined by energy dispersive X-ray analysis, and the zinc concentration was confirmed by inductively coupled plasma mass spectroscopy and cathodoluminescence measurements. The resistivity value was in the range of 8 Â 10 8 U cm, being smaller for the passivated sample, which at the same time had counter device properties.
The interest of rare earth doping of semiconductors has increased in the last years due to its po... more The interest of rare earth doping of semiconductors has increased in the last years due to its possible applications in optical devices requiring temperature stability. Advantages of these systems are the presence of a sharp temperature independent rare-earth luminescence and the possibility of activation of the emitting rare-earth centers by minority carrier injection. In this work the effect of erbium doping on the luminescence and on the native accepters of GaSb crystals has been investigated by CL-SEM. Er doping has been found to increase the total CL intensity and to produce spectral changes that depend on the erbium concentration. At moderate doping the native acceptor concentration, as detected by the luminescence band A, decreases. At high Er concentrations Er-Sb precipitates form and doping appears not to be efficient in the suppression of accepters. X-ray microanalysis reveals that the composition of the precipitates is Er-5 Sb-3. Emission from intraionic transitions of Er...
Acta Materialia, 2020
Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devic... more Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devices. Herein, we investigate the UV luminescence of zinc germanate Zn 2 GeO 4 microwires by means of photoluminescence measurements as a function of temperature and excitation conditions. The emitted UV light is composed of two bands (a broad one and a narrow one) associated with the native defects structure. In addition, with the aid of density functional theory (DFT) calculations, the energy positions of the electronic levels related to native defects in Zn 2 GeO 4 have been calculated. In particular, our results support that zinc interstitials are the responsible for the narrow UV band, which is, in turn, split into two components with different temperature dependence 1 arXiv:2007.15336v1 [cond-mat.mtrl-sci] 30 Jul 2020 behaviour. The origin of the two components is explained on the basis of the particular location of Zn i in the lattice and agrees with DFT calculations. Furthermore, a kinetic luminescence model is proposed to ascertain the temperature evolution of this UV emission. These results pave the way to exploit defect engineering in achieving functional optoelectronic devices to operate in the UV region.
RSC Advances, 2020
The growth mechanism of layered α-MoO3 nano- and microplates on the surface of Mo wires during Jo... more The growth mechanism of layered α-MoO3 nano- and microplates on the surface of Mo wires during Joule heating has been investigated by application of an external electric field to the current carrying wire.
Scientific Reports, 2019
We report on a novel implementation of the cryo-etching method, which enabled us to fabricate low... more We report on a novel implementation of the cryo-etching method, which enabled us to fabricate low-roughness hBN-encapsulated graphene nanoconstrictions with unprecedented control of the structure edges; the typical edge roughness is on the order of a few nanometers. We characterized the system by atomic force microscopy and used the measured parameters of the edge geometry in numerical simulations of the system conductance, which agree quantitatively with our low temperature transport measurements. The quality of our devices is confirmed by the observation of well defined quantized 2e2/h conductance steps at zero magnetic field. To the best of our knowledge, such an observation reports the clearest conductance quantization in physically etched graphene nanoconstrictions. The fabrication of such high quality systems and the scalability of the cryo-etching method opens a novel promising possibility of producing more complex truly-ballistic devices based on graphene.
Solid State Communications, 1998
The effect of aluminium on the defect structure of GaSb crystals, grown by the vertical Bridgman ... more The effect of aluminium on the defect structure of GaSb crystals, grown by the vertical Bridgman technique, has been investigated by cathodoluminescence (CL) in the scanning electron microscope. Crystals have been found to be highly homogeneous along the growth axis with the exception of the top end which showed Al accumulation. The CL results show decoration of extended defects by Al but contrary to the case of other dopants Al has not been found to cause a significative reduction of native acceptors. A CL band at about 850 meV appears to be related to the presence of aluminium.
Semiconductor Science and Technology, 1998
GaSb single crystals with different Er concentrations have been studied by cathodoluminescence in... more GaSb single crystals with different Er concentrations have been studied by cathodoluminescence in the scanning electron microscope. Low Er doping has been found to reduce the concentration of native acceptors. In crystals with higher Er concentrations, Er-Sb precipitates form and doping becomes less efficient in suppressing the acceptors. In these samples intraionic Er luminescence is observed.
physica status solidi (c), 2005
This paper presents cathodoluminescence, electrical and structural characteristics of (11-20)-ori... more This paper presents cathodoluminescence, electrical and structural characteristics of (11-20)-oriented 4H-SiC substrates, aiming at determining properties of some extended defects. As-grown basal plane dislocations with the Burgers vector b = 1/3 <11-20> previously revealed to be associated to a radiative recombination level at 1.80 eV. Well controlled dislocations were here introduced by annealing the sample under compressive stress at 973 K. After the annealing, double stacking faults were detected, formed by two Shockley partial dislocations gliding in two successive basal planes. These defects proved to introduce a rectifying behaviour during forward voltage operation, with a corresponding barrier height value of 0.58 eV at room temperature. Cathodoluminescence measurements allowed to attribute a radiative level at 1.80 eV to the extended defects, giving rise to a double luminescence peak.
Materials Science and Engineering: B, 2001
In this work pure and Gd-doped GaSb ingots with different dopant concentrations were grown by the... more In this work pure and Gd-doped GaSb ingots with different dopant concentrations were grown by the Bridgman Method. The compositional and electrical analysis carried out on these materials have shown the dependence of these results on the initial dopant concentration. The analysis have revealed the presence of inclusions which have been identified as Gd-Sb precipitates. The doped material was found to be p-type with a maximum value of the carrier density at the central region of the ingots. It has been also demonstrated that the Gd enhances the A band emission reducing the band-gap emission.
Materials Science and Engineering: B, 2001
We report here the studies carried out in zinc diffused n-type GaSb by cathodoluminescence (CL) m... more We report here the studies carried out in zinc diffused n-type GaSb by cathodoluminescence (CL) microscopy and by scanning tunneling spectroscopy. Samples with different diffusion profiles measured by secondary ion mass spectrometry (SIMS) were obtained. CL plan-view observations show high homogeneity in the diffused layers. Cross-sectional measurements of the Zn diffused layers were performed by current imaging tunneling spectroscopy (CITS). The junction border was revealed clearly in the CITS images and conductance spectra recorded at differents points of the layers provided information on the local surface band gaps and the conductive behaviour. The results were related to the diffusion profiles and were found to agree with diffusion models suggested previously.
Materials Science and Engineering: A, 2010
The microstructure and mechanical properties in the interface region of a multilayer composite la... more The microstructure and mechanical properties in the interface region of a multilayer composite laminate based on Al-Zn (Al 7075) and Al-Cu (Al 2024) alloys have been mainly characterized by EBSD and shear tests. It is shown that varying solution heat treatments affect the microstructure of the constituent aluminium alloys in the bonding region and, as a consequence, the interfacial mechanical properties. The increase in the solution treatment time improves the interfacial toughness of the multilayer aluminium laminate due to higher intrinsic toughness of the constituent aluminium alloys.
Journal of Crystal Growth, 2002
Nd-doped GaSb bulk crystals with three different dopant concentrations have been grown by the ver... more Nd-doped GaSb bulk crystals with three different dopant concentrations have been grown by the vertical Bridgman technique. The axial segregation has been characterised by obtaining the effective segregation coefficient. Differences in the value of this coefficient show its dopant concentration dependence. Resistivity, carrier density and mobility have also been obtained showing the p-type nature of this material. Structural and compositional properties have been studied revealing some inclusions with high Nd concentration in the highest Nd-doped ingot.
Journal of Crystal Growth, 2008
Cadmium telluride (CdTe) crystals and epitaxial layers were grown by the vertical Bridgman method... more Cadmium telluride (CdTe) crystals and epitaxial layers were grown by the vertical Bridgman method and vapor-phase epitaxy, respectively, to obtain the high-resistive material suitable for X-and gamma-ray detectors. The crystals and layers were doped with Ge at the concentration of 5 Â 10 17 cm À3 and co-doped with the rare element Yb at the concentration range from 1 Â 10 17 to 1 Â 10 19 cm À3. The CdTe:Ge:Yb samples were studied by the structural and electrical characterization techniques, low-temperature photoluminescence (PL) and cathodoluminescence (CL) spectroscopy and CL imaging. Experimental findings testify that homogeneous crystals and layers of reasonably good structural quality can be grown with the Yb concentration below the value of 5 Â 10 18 cm À3 that is estimated to be the limit for Yb solubility in CdTe:Ge:Yb. These findings seem to be related with the purification effect caused by the interaction of the Yb dopant with the group I residual impurities.
Journal of Applied Physics, 2010
The II-VI compound semiconductor cadmium zinc telluride ͑CZT͒ is very useful for room temperature... more The II-VI compound semiconductor cadmium zinc telluride ͑CZT͒ is very useful for room temperature radiation detection applications. In the present research, we have successfully grown Bi doped CZT single crystals with two different zinc concentrations ͑8 and 14 at. %͒ by the Bridgman oscillation method, in which one experiment has been carried out with a platinum ͑Pt͒ tube as the ampoule support. Pt also acts as a cold finger and reduces the growth velocity and enhances crystalline perfection. The grown single crystals have been studied with different analysis methods. The stoichiometry was confirmed by energy dispersive by x-ray and inductively coupled plasma mass spectroscopy analyses and it was found there is no incorporation of impurities in the grown crystal. The presence of Cd and Te vacancies was determined by cathodoluminescence studies. Electrical properties were assessed by I-V analysis and indicated higher resistive value ͑8.53 ϫ 10 8 ⍀ cm͒ for the crystal grown with higher zinc concentration ͑with Cd excess͒ compare to the other ͑3.71ϫ 10 5 ⍀ cm͒.
The European Physical Journal Applied Physics, 2004
Silicon Carbide (SiC) is a wide band gap semiconductor, having opto-electronic properties that ar... more Silicon Carbide (SiC) is a wide band gap semiconductor, having opto-electronic properties that are suitable for many applications. Some structural defects due to crystal growth and/or doping technologies are commonly present in the substrates of SiC. The (1120)-oriented 4H-SiC bulk wafers are particularly investigated, due to some advantages with respect to the (0001)-Si face. One of these advantages is a better crystal reordering during post-implantation annealing. In this paper cathodoluminescence (CL) and X-Ray topography measurements have been carried out in order to investigate the optical and structural properties of commercial (1120) 4H n +-type substrates.