J. Škriniarová - Academia.edu (original) (raw)

Papers by J. Škriniarová

Japanese Journal of Applied Physics, 2001

The order-dependent direct-gap reduction and valence-band splitting in spontaneously ordered indi... more The order-dependent direct-gap reduction and valence-band splitting in spontaneously ordered indirect-gap AlInP2 are determined by polarized piezoreflectance spectroscopy at room temperature. The experimentally deduced values of the ratio of band-gap reduction to crystal field splitting for the perfectly ordered alloys, ζ=-ΔE g (1)/ΔCF (1)=1.15, and the ratio of band-gap reduction to the ordering change of spin-orbit splitting between the perfectly ordered and random alloys, ξ=-ΔE g (1)/[ΔSO (1)-ΔSO (0)]=8.24, are in good agreement with the recent theoretically calculated value of 1.13 and 13.5, respectively, by [S. H. Wei and A. Zunger. Phys. Rev. B 57, (1998) 8983] but are much larger than those of the previous report by [M. Schubert et al..: Phys. Rev. B 54 (1996) 17616] using dark-field spectroscopy.

Journal of Applied Physics, 2010

Ni/AlGaN/GaN Schottky barrier diodes were characterized by electrical and optical measurements. A... more Ni/AlGaN/GaN Schottky barrier diodes were characterized by electrical and optical measurements. Analysis of temperature-dependent (80 K to 550 K) current-voltage characteristics considering various transport mechanisms shows that the tunneling current dominates in the samples investigated. Thermionic emission current, extracted from the total current by a fitting procedure, yielded an effective barrier height of 1.36 eV to 1.39 eV at 300 K, and its slight decrease with increased temperature. This result shows that significantly lower barrier heights reported before (0.73 eV to 0.96 eV) follow from an assumption that the measured and thermionic currents are equal. The barrier height of 1.66 eV extracted from photoemission measurements confirms that electrically evaluated barrier heights are underestimated. The tunneling current contribution is considered to be dislocation governed, and a dislocation density of about 2 9 10 8 cm À2 is calculated.

In this article we describe the electron-beam direct-write (EBDW) lithography [1] process for the... more In this article we describe the electron-beam direct-write (EBDW) lithography [1] process for the AZ 5214E photoresist (Clariant Corporation, Switzerland) [2] which is, besides its sensitivity to UV radiation, to some extent sensitive also to electrons. This special photoresist is normally intended for lift-off-techniques which call for a negative wall profile. Although it is positive photoresists comprised of a novolak resin and naphthoquinone diazide as photoactive compound (PAC), it is also capable of usage as an image reversal (IR) and it is mostly used in this mode also for its excellent dry etch resistance and thermal stability. Its IR capability is obtained by a special crosslinking agent which becomes active at temperatures above 110°C and only in exposed areas of the resist. The crosslinking agent together with exposed PAC leads to an almost insoluble (in developer) and no longer light sensitive substance, while the unexposed areas still behave like a normal unexposed posit...

Optik, 2021

Abstract In this paper we focus on investigation of GaP volume fraction in GaP nanowires (NWs) pr... more Abstract In this paper we focus on investigation of GaP volume fraction in GaP nanowires (NWs) prepared on GaP substrates by MOVPE using VLS mode. For this purpose, spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM) image processing methods were used showing a good agreement. In ellipsometry, composition of GaP and void was modeled using linear gradient model in combination with Bruggeman Effective Medium Approximation (BEMA). From this model the volume fraction of GaP on the top of the nanowires was determined from 1.5%–6.3%) and in the bottom of the nanowires from 34.8%–39.6%), respectively. The histogram of GaP nanowires SEM image was divided into 10 bins above the plane. The volume fraction of GaP nanowires determined from these bins ranged from 1.4 % to 3.8 % on the top of the nanowires and from 33.5%–46.2% in their bottom. Linearity of the SEM histogram bins gradient was further compared to the linearity of the linear gradient layer model.

Applied Surface Science, 2017

Abstract In this paper we show a comparison of chosen lithographies used for the AZ 5214E photore... more Abstract In this paper we show a comparison of chosen lithographies used for the AZ 5214E photoresist, which is normally UV sensitive but has also been investigated for its sensitivity to e-beam exposure. Three lithographies, the E-Beam Direct Write lithography (EBDW), laser Interference Lithography (IL) and the non-contact Near-field Scanning Optical Microscopy (NSOM) lithography, are discussed here and the results on exposed arrays of simple patterns are shown. With the EBDW and IL we achieved periods of the structures around half-micron, and we demonstrate attainability of dimensions smaller or comparable than usually achieved by a standard optical photolithography with the investigated photoresist. With the non-contact NSOM lithography structures with periods slightly above a micron were achieved.

Applied Surface Science, 2017

The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or ... more The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or on a ZnO thin film doped by Ga is demonstrated. Statistical analysis of morphology images (SEM, AFM) exhibited the Log-normal distribution of the size (area) of nanoislands-their modus A M varied from 8 to 328 nm 2 depending on the sputtering power density, which determined the nominal thicknesses in the range of 2-8 nm. Preferential polycrystalline texture (111) of Au NIA increased with the power density and after annealing. Transverse localised surface plasmonic resonance (LSPR; evaluated by transmission UV-vis spectroscopy) showed the red shift of the extinction peaks (l ≤ 100 nm) with an increase of the nominal thickness, and the blue shift (≤ −65 nm) after annealing of Au NIA. The plasmonic behaviour of Au NIA was described by modification of a size-scaling universal model using the nominal thin film thickness as a technological scaling parameter. Sputtering of a Ti intermediate adhesive ultrathin film between the glass substrate and gold improves the adhesion of Au nanoislands as well as supporting the formation of more defined Au NIA structures of smaller dimensions.

Plasmonics: Metallic Nanostructures and Their Optical Properties XIII, 2015

In this paper we present optical properties of thin metal films deposited on the glass substrates... more In this paper we present optical properties of thin metal films deposited on the glass substrates by the physical vapor deposition. Localized surface plasmon polaritons of different film thicknesses have been spectrally characterized by optical methods. Evidence of the Au nanoparticles in deposited thin films have been demonstrated by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) and their dimensions as well as separations have been evaluated. As a first approximation, the simulation model of deposited nanoparticles without assuming their dimension and separation distributions has been created. Simulation model defines relation between the nanoparticle dimensions and their separations. Model of deposited nanoparticles has been simulated by the Finite-Difference Time-Domain (FDTD) simulation method. The pulsed excitation has been used and transmission of optical radiation has been calculated from the spectral response by Fast Fourier Transform (FFT) analyses. Plasmonic extinctions have been calculated from measured spectral characteristics as well as simulated characteristics and compared with each other. The nanoparticle dimensions and separations have been evaluated from the agreement between the simulation and experimental spectral characteristics. Surface morphology of thin metal film has been used as an input for the detail simulation study based on the experimental observation of metal nanoparticle distribution. Hence, this simulation method includes appropriate coupling effects between nanoparticles and provides more reliable results. Obtained results are helpful for further deep understanding of thin metal films plasmonic properties and simulation method is demonstrated as a powerful tool for the deposition technology optimizations.

Nanoengineering: Fabrication, Properties, Optics, and Devices XII, 2015

In this paper we focus on the application of the one-dimensional photonic crystal (1D PhC) struct... more In this paper we focus on the application of the one-dimensional photonic crystal (1D PhC) structures on the top of Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (MQW LED). 1D PhC structures with periods of 600 nm, 700 nm, 800 nm, and 900 nm were fabricated by the E-Beam Direct Write (EBDW) Lithography. Effect of 1D PhC period on the light extraction enhancement was studied. 1D PhC LED radiation profiles were obtained from Near Surface Light Emission Images (NSLEI). Measurements showed the strongest light extraction enhancement using 800 nm period of PhC. Investigation of PhC LED radiation profiles showed strong light decoupling when light reaches PhC structure. Achieved LEE was from 22.6% for 600 nm PhC LED to 47.0% for 800 nm PhC LED. LED with PhC structure at its surface was simulated by FDTD simulation method under excitation of appropriate launch field.

Heterostructure Epitaxy and Devices, 1996

Heterostructure Epitaxy and Devices — HEAD’97, 1998

The Eighth International Conference on Advanced Semiconductor Devices and Microsystems, 2010

... Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego Stree... more ... Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego Street 11/17, 50-372 Wroclaw, Poland 3 Institute of Electrical Engineering SAS, Dúbravská cesta 9, 841 04 e-mail: lubica.stuchlikova@stuba.sk, jan.sebok@stuba.sk, jakub.rybar@stuba ...

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2001

Photoelectrochemical etching ͑PEC͒ of n ϩ-GaN in KOH and AZ400K photoresist developer is presente... more Photoelectrochemical etching ͑PEC͒ of n ϩ-GaN in KOH and AZ400K photoresist developer is presented. We compare the two solutions used for PEC etching without an external bias. The influence of etchant concentration and of the intensity of ultraviolet illumination was studied with emphasis on the resulting etched surface quality. The quality of the shallow etched surface and its roughness are presented. The AZ400K etchant was applied to shallow etching of n ϩ-GaN with threading dislocation densities in the range of 10 9-10 10 cm Ϫ2. Moreover, the first analysis of photocurrent monitoring during the electrochemical etching of GaN epitaxial layers in KOH is presented. We found that photocurrent very sensitively reflected the changes in the quality of the etched surface.

Applied Surface Science, 2015

ABSTRACT ZnO is a prominent material for creation of nanostructures as a multifunctional material... more ABSTRACT ZnO is a prominent material for creation of nanostructures as a multifunctional material for broad applications in blue and ultraviolet optoelectronics. A lot of efforts have been dedicated to understand the unique properties of nanostructured materials. The main purpose of this work is to verify (1) the technology of thin ZnO films deposition by RF magnetron sputtering to cover round GaP nanowires prepared by metalorganic vapor phase epitaxy, and (2) the hydrothermal growth of core/shell ZnO nanostructures on both GaP/ZnO and GaP/ZnO structures and nanowires deposited by RF magnetron sputtering. SEM, XRD, optical ellipsometry and micro-Raman measurements were employed to investigate the structural and optical properties of GaP/ZnO structures as well as core/shell nanostructures. The thickness, columnar structure and surface layer roughness of the deposited ZnO layers were estimated from cut-edge SEM images and verified by spectral ellipsometry. The measured XRD intensity patterns of (0 0 2) ZnO line of hydrothermally grown ZnO nanoclusters on nanowires show a narrow spectral width ∼0.17° which indicates a good crystalline structure in comparison with ZnO films prepared by magnetron sputtering on GaP substrate, even after their annealing. The PL spectra of the hydrothermally grown GaP/ZnO core/shell nanostructure show typical near band emission and very strong yellow broadband emission from Zn(OH)2 or hydroxyl groups for ZnO structures. For the first time we have demonstrated formation of GaP/ZnO core/shell nanostructured arrays on GaP nanowires grown by hydrothermal process.

19th Polish-Slovak-Czech Optical Conference on Wave and Quantum Aspects of Contemporary Optics, 2014

ABSTRACT In this work we focus on the application of the two dimensional photonic crystal (2D PhC... more ABSTRACT In this work we focus on the application of the two dimensional photonic crystal (2D PhC) embedded in the surface of Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (LED) to enable improvement of the light extraction from the LEDs. The 2D PhC structures described in this contribution were fabricated by the E-Beam Direct Write (EBDW) Lithography and consist of pillars with the period of 700 nm. In this paper a new approach is presented to measure the PhC-LEDs based on evaluating light-current characteristics from Near Surface Light Emission Image (NSLEI) measurements in comparison with standard light-current characteristics measured by integrating sphere. The measured LED emission intensity increased by 20-30% when PhC was patterned on the top of LED structure in comparison with the reference LED without PhC. In addition, it was found that the measured light extraction intensity is higher in the case of NSLEI measurements. This originates in the ability that mostly the light intensity emitted from the LED surface is measured while the edge emission effect is suppressed.

Microelectronics Journal, 2006

An InGaAs/InP avalanche photodiode (APD) with a sectional InGaAsP/InP charge layer at the heteroi... more An InGaAs/InP avalanche photodiode (APD) with a sectional InGaAsP/InP charge layer at the heterointerface between the InGaAs absorption and InP multiplication region has been designed, fabricated and tested. We demonstrate a new APD structure that utilizes the sectional 140nm thin charge layer and a 500nm thin multiplication layer. The band diagram, electrical field distribution and current–voltage (I–V) characteristics up to

Optics & Laser Technology, 2011

We present a light emitting diode with a two-dimensional photonic crystal structure prepared by i... more We present a light emitting diode with a two-dimensional photonic crystal structure prepared by interference lithography at the light emitting diode surface. The emission maximum is at 850 nm. The two-dimensional photonic crystal structure enhanced the light extraction efficiency by a factor of 1.39. The photonic crystal light emitting diode surface morphology was analyzed by atomic force microscopy. The enhanced extraction efficiency of the photonic crystal diode was documented from L(I) dependencies and was confirmed by near-field studies.

Vacuum, 2001

Two different approaches for the HFET's T-shaped gate fabrication are presented. ... more Two different approaches for the HFET's T-shaped gate fabrication are presented. Besides the conventional approach based on the three-layer resist structure a new one based on the poly Si/polyimide bilayer is demonstrated using which a ratio of the gate head length to the gate foot length larger than 10 is achieved. Both of the fabrication techniques presented seem to be

Physica Status Solidi (a), 1995

ABSTRACT

Microelectronics Journal, 2009

We have prepared, characterized and discussed the performance of AlGaAs/GaAs heterojunction bipol... more We have prepared, characterized and discussed the performance of AlGaAs/GaAs heterojunction bipolar phototransistor (HPT) including Zn delta-doped base. Due to the existence of d-doped sheets located in the middle of undoped GaAs base the d-doped HPT devices exhibit low dark current, nearly zero offset voltage, saturation voltage 0.4V,andriseandfalltimesinnsrangeatwavelengthof850nmupto6Vofappliedvoltage.Duetoavalanchemultiplicationbehavioratthecollectorjunction,anincreasedopticalgainG410canbereachedforappliedvoltagesintherangeof6−12V.Forvoltageshigherthanthedevicebreakdownvoltage(0.4 V, and rise and fall times in ns range at wavelength of 850 nm up to 6 V of applied voltage. Due to avalanche multiplication behavior at the collector junction, an increased optical gain G410 can be reached for applied voltages in the range of 6-12 V. For voltages higher than the device breakdown voltage (0.4V,andriseandfalltimesinnsrangeatwavelengthof850nmupto6Vofappliedvoltage.Duetoavalanchemultiplicationbehavioratthecollectorjunction,anincreasedopticalgainG410canbereachedforappliedvoltagesintherangeof6−12V.Forvoltageshigherthanthedevicebreakdownvoltage(12 V) switching and negative differential resistance (NDR) effect is measurable in the inverted mode of operation.

Japanese Journal of Applied Physics, 2001

The order-dependent direct-gap reduction and valence-band splitting in spontaneously ordered indi... more The order-dependent direct-gap reduction and valence-band splitting in spontaneously ordered indirect-gap AlInP2 are determined by polarized piezoreflectance spectroscopy at room temperature. The experimentally deduced values of the ratio of band-gap reduction to crystal field splitting for the perfectly ordered alloys, ζ=-ΔE g (1)/ΔCF (1)=1.15, and the ratio of band-gap reduction to the ordering change of spin-orbit splitting between the perfectly ordered and random alloys, ξ=-ΔE g (1)/[ΔSO (1)-ΔSO (0)]=8.24, are in good agreement with the recent theoretically calculated value of 1.13 and 13.5, respectively, by [S. H. Wei and A. Zunger. Phys. Rev. B 57, (1998) 8983] but are much larger than those of the previous report by [M. Schubert et al..: Phys. Rev. B 54 (1996) 17616] using dark-field spectroscopy.

Journal of Applied Physics, 2010

Ni/AlGaN/GaN Schottky barrier diodes were characterized by electrical and optical measurements. A... more Ni/AlGaN/GaN Schottky barrier diodes were characterized by electrical and optical measurements. Analysis of temperature-dependent (80 K to 550 K) current-voltage characteristics considering various transport mechanisms shows that the tunneling current dominates in the samples investigated. Thermionic emission current, extracted from the total current by a fitting procedure, yielded an effective barrier height of 1.36 eV to 1.39 eV at 300 K, and its slight decrease with increased temperature. This result shows that significantly lower barrier heights reported before (0.73 eV to 0.96 eV) follow from an assumption that the measured and thermionic currents are equal. The barrier height of 1.66 eV extracted from photoemission measurements confirms that electrically evaluated barrier heights are underestimated. The tunneling current contribution is considered to be dislocation governed, and a dislocation density of about 2 9 10 8 cm À2 is calculated.

In this article we describe the electron-beam direct-write (EBDW) lithography [1] process for the... more In this article we describe the electron-beam direct-write (EBDW) lithography [1] process for the AZ 5214E photoresist (Clariant Corporation, Switzerland) [2] which is, besides its sensitivity to UV radiation, to some extent sensitive also to electrons. This special photoresist is normally intended for lift-off-techniques which call for a negative wall profile. Although it is positive photoresists comprised of a novolak resin and naphthoquinone diazide as photoactive compound (PAC), it is also capable of usage as an image reversal (IR) and it is mostly used in this mode also for its excellent dry etch resistance and thermal stability. Its IR capability is obtained by a special crosslinking agent which becomes active at temperatures above 110°C and only in exposed areas of the resist. The crosslinking agent together with exposed PAC leads to an almost insoluble (in developer) and no longer light sensitive substance, while the unexposed areas still behave like a normal unexposed posit...

Optik, 2021

Abstract In this paper we focus on investigation of GaP volume fraction in GaP nanowires (NWs) pr... more Abstract In this paper we focus on investigation of GaP volume fraction in GaP nanowires (NWs) prepared on GaP substrates by MOVPE using VLS mode. For this purpose, spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM) image processing methods were used showing a good agreement. In ellipsometry, composition of GaP and void was modeled using linear gradient model in combination with Bruggeman Effective Medium Approximation (BEMA). From this model the volume fraction of GaP on the top of the nanowires was determined from 1.5%–6.3%) and in the bottom of the nanowires from 34.8%–39.6%), respectively. The histogram of GaP nanowires SEM image was divided into 10 bins above the plane. The volume fraction of GaP nanowires determined from these bins ranged from 1.4 % to 3.8 % on the top of the nanowires and from 33.5%–46.2% in their bottom. Linearity of the SEM histogram bins gradient was further compared to the linearity of the linear gradient layer model.

Applied Surface Science, 2017

Abstract In this paper we show a comparison of chosen lithographies used for the AZ 5214E photore... more Abstract In this paper we show a comparison of chosen lithographies used for the AZ 5214E photoresist, which is normally UV sensitive but has also been investigated for its sensitivity to e-beam exposure. Three lithographies, the E-Beam Direct Write lithography (EBDW), laser Interference Lithography (IL) and the non-contact Near-field Scanning Optical Microscopy (NSOM) lithography, are discussed here and the results on exposed arrays of simple patterns are shown. With the EBDW and IL we achieved periods of the structures around half-micron, and we demonstrate attainability of dimensions smaller or comparable than usually achieved by a standard optical photolithography with the investigated photoresist. With the non-contact NSOM lithography structures with periods slightly above a micron were achieved.

Applied Surface Science, 2017

The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or ... more The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or on a ZnO thin film doped by Ga is demonstrated. Statistical analysis of morphology images (SEM, AFM) exhibited the Log-normal distribution of the size (area) of nanoislands-their modus A M varied from 8 to 328 nm 2 depending on the sputtering power density, which determined the nominal thicknesses in the range of 2-8 nm. Preferential polycrystalline texture (111) of Au NIA increased with the power density and after annealing. Transverse localised surface plasmonic resonance (LSPR; evaluated by transmission UV-vis spectroscopy) showed the red shift of the extinction peaks (l ≤ 100 nm) with an increase of the nominal thickness, and the blue shift (≤ −65 nm) after annealing of Au NIA. The plasmonic behaviour of Au NIA was described by modification of a size-scaling universal model using the nominal thin film thickness as a technological scaling parameter. Sputtering of a Ti intermediate adhesive ultrathin film between the glass substrate and gold improves the adhesion of Au nanoislands as well as supporting the formation of more defined Au NIA structures of smaller dimensions.

Plasmonics: Metallic Nanostructures and Their Optical Properties XIII, 2015

In this paper we present optical properties of thin metal films deposited on the glass substrates... more In this paper we present optical properties of thin metal films deposited on the glass substrates by the physical vapor deposition. Localized surface plasmon polaritons of different film thicknesses have been spectrally characterized by optical methods. Evidence of the Au nanoparticles in deposited thin films have been demonstrated by Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) and their dimensions as well as separations have been evaluated. As a first approximation, the simulation model of deposited nanoparticles without assuming their dimension and separation distributions has been created. Simulation model defines relation between the nanoparticle dimensions and their separations. Model of deposited nanoparticles has been simulated by the Finite-Difference Time-Domain (FDTD) simulation method. The pulsed excitation has been used and transmission of optical radiation has been calculated from the spectral response by Fast Fourier Transform (FFT) analyses. Plasmonic extinctions have been calculated from measured spectral characteristics as well as simulated characteristics and compared with each other. The nanoparticle dimensions and separations have been evaluated from the agreement between the simulation and experimental spectral characteristics. Surface morphology of thin metal film has been used as an input for the detail simulation study based on the experimental observation of metal nanoparticle distribution. Hence, this simulation method includes appropriate coupling effects between nanoparticles and provides more reliable results. Obtained results are helpful for further deep understanding of thin metal films plasmonic properties and simulation method is demonstrated as a powerful tool for the deposition technology optimizations.

Nanoengineering: Fabrication, Properties, Optics, and Devices XII, 2015

In this paper we focus on the application of the one-dimensional photonic crystal (1D PhC) struct... more In this paper we focus on the application of the one-dimensional photonic crystal (1D PhC) structures on the top of Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (MQW LED). 1D PhC structures with periods of 600 nm, 700 nm, 800 nm, and 900 nm were fabricated by the E-Beam Direct Write (EBDW) Lithography. Effect of 1D PhC period on the light extraction enhancement was studied. 1D PhC LED radiation profiles were obtained from Near Surface Light Emission Images (NSLEI). Measurements showed the strongest light extraction enhancement using 800 nm period of PhC. Investigation of PhC LED radiation profiles showed strong light decoupling when light reaches PhC structure. Achieved LEE was from 22.6% for 600 nm PhC LED to 47.0% for 800 nm PhC LED. LED with PhC structure at its surface was simulated by FDTD simulation method under excitation of appropriate launch field.

Heterostructure Epitaxy and Devices, 1996

Heterostructure Epitaxy and Devices — HEAD’97, 1998

The Eighth International Conference on Advanced Semiconductor Devices and Microsystems, 2010

... Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego Stree... more ... Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego Street 11/17, 50-372 Wroclaw, Poland 3 Institute of Electrical Engineering SAS, Dúbravská cesta 9, 841 04 e-mail: lubica.stuchlikova@stuba.sk, jan.sebok@stuba.sk, jakub.rybar@stuba ...

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2001

Photoelectrochemical etching ͑PEC͒ of n ϩ-GaN in KOH and AZ400K photoresist developer is presente... more Photoelectrochemical etching ͑PEC͒ of n ϩ-GaN in KOH and AZ400K photoresist developer is presented. We compare the two solutions used for PEC etching without an external bias. The influence of etchant concentration and of the intensity of ultraviolet illumination was studied with emphasis on the resulting etched surface quality. The quality of the shallow etched surface and its roughness are presented. The AZ400K etchant was applied to shallow etching of n ϩ-GaN with threading dislocation densities in the range of 10 9-10 10 cm Ϫ2. Moreover, the first analysis of photocurrent monitoring during the electrochemical etching of GaN epitaxial layers in KOH is presented. We found that photocurrent very sensitively reflected the changes in the quality of the etched surface.

Applied Surface Science, 2015

ABSTRACT ZnO is a prominent material for creation of nanostructures as a multifunctional material... more ABSTRACT ZnO is a prominent material for creation of nanostructures as a multifunctional material for broad applications in blue and ultraviolet optoelectronics. A lot of efforts have been dedicated to understand the unique properties of nanostructured materials. The main purpose of this work is to verify (1) the technology of thin ZnO films deposition by RF magnetron sputtering to cover round GaP nanowires prepared by metalorganic vapor phase epitaxy, and (2) the hydrothermal growth of core/shell ZnO nanostructures on both GaP/ZnO and GaP/ZnO structures and nanowires deposited by RF magnetron sputtering. SEM, XRD, optical ellipsometry and micro-Raman measurements were employed to investigate the structural and optical properties of GaP/ZnO structures as well as core/shell nanostructures. The thickness, columnar structure and surface layer roughness of the deposited ZnO layers were estimated from cut-edge SEM images and verified by spectral ellipsometry. The measured XRD intensity patterns of (0 0 2) ZnO line of hydrothermally grown ZnO nanoclusters on nanowires show a narrow spectral width ∼0.17° which indicates a good crystalline structure in comparison with ZnO films prepared by magnetron sputtering on GaP substrate, even after their annealing. The PL spectra of the hydrothermally grown GaP/ZnO core/shell nanostructure show typical near band emission and very strong yellow broadband emission from Zn(OH)2 or hydroxyl groups for ZnO structures. For the first time we have demonstrated formation of GaP/ZnO core/shell nanostructured arrays on GaP nanowires grown by hydrothermal process.

19th Polish-Slovak-Czech Optical Conference on Wave and Quantum Aspects of Contemporary Optics, 2014

ABSTRACT In this work we focus on the application of the two dimensional photonic crystal (2D PhC... more ABSTRACT In this work we focus on the application of the two dimensional photonic crystal (2D PhC) embedded in the surface of Al0.295Ga0.705As/GaAs multi-quantum well light emitting diode (LED) to enable improvement of the light extraction from the LEDs. The 2D PhC structures described in this contribution were fabricated by the E-Beam Direct Write (EBDW) Lithography and consist of pillars with the period of 700 nm. In this paper a new approach is presented to measure the PhC-LEDs based on evaluating light-current characteristics from Near Surface Light Emission Image (NSLEI) measurements in comparison with standard light-current characteristics measured by integrating sphere. The measured LED emission intensity increased by 20-30% when PhC was patterned on the top of LED structure in comparison with the reference LED without PhC. In addition, it was found that the measured light extraction intensity is higher in the case of NSLEI measurements. This originates in the ability that mostly the light intensity emitted from the LED surface is measured while the edge emission effect is suppressed.

Microelectronics Journal, 2006

An InGaAs/InP avalanche photodiode (APD) with a sectional InGaAsP/InP charge layer at the heteroi... more An InGaAs/InP avalanche photodiode (APD) with a sectional InGaAsP/InP charge layer at the heterointerface between the InGaAs absorption and InP multiplication region has been designed, fabricated and tested. We demonstrate a new APD structure that utilizes the sectional 140nm thin charge layer and a 500nm thin multiplication layer. The band diagram, electrical field distribution and current–voltage (I–V) characteristics up to

Optics & Laser Technology, 2011

We present a light emitting diode with a two-dimensional photonic crystal structure prepared by i... more We present a light emitting diode with a two-dimensional photonic crystal structure prepared by interference lithography at the light emitting diode surface. The emission maximum is at 850 nm. The two-dimensional photonic crystal structure enhanced the light extraction efficiency by a factor of 1.39. The photonic crystal light emitting diode surface morphology was analyzed by atomic force microscopy. The enhanced extraction efficiency of the photonic crystal diode was documented from L(I) dependencies and was confirmed by near-field studies.

Vacuum, 2001

Two different approaches for the HFET's T-shaped gate fabrication are presented. ... more Two different approaches for the HFET's T-shaped gate fabrication are presented. Besides the conventional approach based on the three-layer resist structure a new one based on the poly Si/polyimide bilayer is demonstrated using which a ratio of the gate head length to the gate foot length larger than 10 is achieved. Both of the fabrication techniques presented seem to be

Physica Status Solidi (a), 1995

ABSTRACT

Microelectronics Journal, 2009

We have prepared, characterized and discussed the performance of AlGaAs/GaAs heterojunction bipol... more We have prepared, characterized and discussed the performance of AlGaAs/GaAs heterojunction bipolar phototransistor (HPT) including Zn delta-doped base. Due to the existence of d-doped sheets located in the middle of undoped GaAs base the d-doped HPT devices exhibit low dark current, nearly zero offset voltage, saturation voltage 0.4V,andriseandfalltimesinnsrangeatwavelengthof850nmupto6Vofappliedvoltage.Duetoavalanchemultiplicationbehavioratthecollectorjunction,anincreasedopticalgainG410canbereachedforappliedvoltagesintherangeof6−12V.Forvoltageshigherthanthedevicebreakdownvoltage(0.4 V, and rise and fall times in ns range at wavelength of 850 nm up to 6 V of applied voltage. Due to avalanche multiplication behavior at the collector junction, an increased optical gain G410 can be reached for applied voltages in the range of 6-12 V. For voltages higher than the device breakdown voltage (0.4V,andriseandfalltimesinnsrangeatwavelengthof850nmupto6Vofappliedvoltage.Duetoavalanchemultiplicationbehavioratthecollectorjunction,anincreasedopticalgainG410canbereachedforappliedvoltagesintherangeof6−12V.Forvoltageshigherthanthedevicebreakdownvoltage(12 V) switching and negative differential resistance (NDR) effect is measurable in the inverted mode of operation.