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Papers by Lutz Kirste

Research paper thumbnail of III-V based high-performance photodetectors in the non-visible regime – from UV to IR

Research paper thumbnail of Preparation of deep UV transparent AlN substrates with high structural perfection for optoelectronic devices

CrystEngComm, 2016

In this paper, the optimal growth conditions during the physical vapour transport of bulk AlN cry... more In this paper, the optimal growth conditions during the physical vapour transport of bulk AlN crystals are evaluated with regard to significantly increased deep UV transparency, while maintaining the high structural quality of the AlN crystals which are grown on N-polar c-facets. We show that carbon concentration [C], oxygen concentration [O], and the ratio between both concentrations [C]/[O] have a significant influence on the deep UV transparency. At 3[C] < [O] with [C] + [O] < 1019 cm−3, deep UV transparent AlN single crystals with absorption coefficients at around 265 nm (α265nm) smaller than 15 cm−1 can be prepared. These conditions can be achieved in the N-polar grown volume parts of the AlN crystals using growth temperatures in the range of TG = 2030–2050 °C and tungsten and tantalum carbide as getter materials for carbon and oxygen, respectively. Deep UV transparent AlN substrates (α265nm < 30 cm−1) ≥10 mm in diameter and of high crystalline perfection (rocking curve FWHM < 15 arcsec) are shown for the first time.

Research paper thumbnail of Optical constants and band gap of wurtzite Al<sub>1−x</sub>Sc<sub>x</sub>N/Al<sub>2</sub>O<sub>3</sub> prepared by magnetron sputter epitaxy for scandium concentrations up to x = 0.41

Journal of Applied Physics, Jul 28, 2019

Research paper thumbnail of Enhanced electromechanical coupling in SAW resonators based on sputtered non-polar Al0.77Sc0.23N 112¯ thin films

Applied Physics Letters, Mar 9, 2020

Research paper thumbnail of Toward AlGaN Focal Plane Arrays for Solar‐Blind Ultraviolet Detection

Physica Status Solidi A-applications and Materials Science, Dec 29, 2019

Research paper thumbnail of Rayleigh waves in nonpolar Al<sub>0.7</sub>Sc<sub>0.3</sub>N(11 2¯0) films with enhanced electromechanical coupling and quality factor

Applied Physics Letters, Nov 7, 2022

Research paper thumbnail of Effect of V/III ratio and growth pressure on surface and crystal quality of AlN grown on sapphire by metal-organic chemical vapor deposition

Journal of vacuum science & technology, May 1, 2022

Research paper thumbnail of Microstructure and mechanical properties of stress-tailored piezoelectric AlN thin films for electro-acoustic devices

Applied Surface Science, Jun 1, 2017

Research paper thumbnail of An advanced Bragg diffraction imaging technique to characterize defects in SiC and GaN : Topic/category, e.g. AM: Advanced Metrology

Research paper thumbnail of Microstructural and optical emission properties of diamond multiply twinned particles

Journal of Applied Physics, Jan 14, 2020

Research paper thumbnail of Al1−xScxN Thin Films at High Temperatures: Sc-Dependent Instability and Anomalous Thermal Expansion

Micromachines, Aug 8, 2022

Research paper thumbnail of InGaAs infrared detector development for SWIR imaging applications

Proceedings of SPIE, Oct 25, 2013

ABSTRACT We report on materials and technology development for short-wave infrared photodetectors... more ABSTRACT We report on materials and technology development for short-wave infrared photodetectors based on InGaAs p-i-n and avalanche photodiodes (APDs). Using molecular beam epitaxy for the growth of thin layers with abrupt interfaces, which are required for optimized APD structures, excellent crystalline quality has been achieved for detector structures grown on 3-inch InP substrates. For the fabrication of focal plane detector arrays, we employed a mesa etching technology in order to compare the results with the commonly utilized planar technology. Camera detector arrays as well as test structures with various sizes and geometries for materials and process characterization are processed using a dry-etch mesa technology. Aspects of the process development are presented along with measured dark-current and photo-current characteristics of the detector devices.

Research paper thumbnail of Improved AlScN/GaN heterostructures grown by metal-organic chemical vapor deposition

Semiconductor Science and Technology, Jan 22, 2021

AlScN/GaN epitaxial heterostructures have raised much interest in recent years, because of the hi... more AlScN/GaN epitaxial heterostructures have raised much interest in recent years, because of the high potential of such structures for high-frequency and high-power electronic applications. Compared to conventional AlGaN/GaN heterostructures, the high spontaneous and piezoelectric polarization of AlScN can yield to a five-time increase in sheet carrier density of the two-dimensional electron gas formed at the AlScN/GaN heterointerface. Very promising radio-frequency device performance has been shown on samples deposited by molecular beam epitaxy. Recently, AlScN/GaN heterostructures have been demonstrated, which were processed by the more industrial compatible growth method metal-organic chemical vapor deposition (MOCVD). In this work, SiN x passivated MOCVD-grown AlScN/GaN heterostructures with improved structural quality have been developed. Analytical transmission electron microscopy, secondary ion mass spectrometry and high-resolution x-ray diffraction analysis indicate the presence of undefined interfaces between the epitaxial layers and an uneven distribution of Al and Sc in the AlScN layer. However, AlScN-based high-electron-mobility transistors (HEMT) have been fabricated and compared with AlN/GaN HEMTs. The device characteristics of the AlScN-based HEMT are promising, showing a transconductance close to 500 mS mm−1 and a drain current above 1700 mA mm−1.

Research paper thumbnail of Electrothermal Performance of AlGaN/GaN Lateral Transistors with >10 μm Thick GaN Buffer on 200 mm Diameter‐Engineered Substrates

Physica Status Solidi A-applications and Materials Science, Jun 19, 2023

Research paper thumbnail of Reduced non-thermal roll-over in violet-emitting GaInN wide-well LEDs grown on low-dislocation-density substrates

Proceedings of SPIE, Feb 12, 2009

Research paper thumbnail of Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs

Acta Physica Polonica A, Nov 1, 2011

Research paper thumbnail of Efficient 350 nm LEDs on low edge threading dislocation density AlGaN buffer layers

Proceedings of SPIE, Feb 10, 2011

Research paper thumbnail of Epitaxial growth of GaInAs/AlGaAsSb quantum cascade lasers

Journal of Crystal Growth, Apr 1, 2007

ABSTRACT

Research paper thumbnail of Current developments for type-II superlattice imaging systems

Proceedings of SPIE, May 13, 2011

InAs/GaSb-based type-II superlattice photodiodes have considerably gained interest as high-perfor... more InAs/GaSb-based type-II superlattice photodiodes have considerably gained interest as high-performance infrared detectors. Beside the excellent properties of InAs/GaSb superlattices, like the relatively high effective electron mass suppressing tunneling currents, the low Auger recombination rate, and a high quantum efficiency, the bandgap can be widely adjusted within the infrared spectral range from 3 - 30 mum depending on the layer thickness

Research paper thumbnail of Plasma affected 2DEG properties on GaN/AlGaN/GaN HEMTs

Physica status solidi, Feb 29, 2012

Research paper thumbnail of III-V based high-performance photodetectors in the non-visible regime – from UV to IR

Research paper thumbnail of Preparation of deep UV transparent AlN substrates with high structural perfection for optoelectronic devices

CrystEngComm, 2016

In this paper, the optimal growth conditions during the physical vapour transport of bulk AlN cry... more In this paper, the optimal growth conditions during the physical vapour transport of bulk AlN crystals are evaluated with regard to significantly increased deep UV transparency, while maintaining the high structural quality of the AlN crystals which are grown on N-polar c-facets. We show that carbon concentration [C], oxygen concentration [O], and the ratio between both concentrations [C]/[O] have a significant influence on the deep UV transparency. At 3[C] < [O] with [C] + [O] < 1019 cm−3, deep UV transparent AlN single crystals with absorption coefficients at around 265 nm (α265nm) smaller than 15 cm−1 can be prepared. These conditions can be achieved in the N-polar grown volume parts of the AlN crystals using growth temperatures in the range of TG = 2030–2050 °C and tungsten and tantalum carbide as getter materials for carbon and oxygen, respectively. Deep UV transparent AlN substrates (α265nm < 30 cm−1) ≥10 mm in diameter and of high crystalline perfection (rocking curve FWHM < 15 arcsec) are shown for the first time.

Research paper thumbnail of Optical constants and band gap of wurtzite Al<sub>1−x</sub>Sc<sub>x</sub>N/Al<sub>2</sub>O<sub>3</sub> prepared by magnetron sputter epitaxy for scandium concentrations up to x = 0.41

Journal of Applied Physics, Jul 28, 2019

Research paper thumbnail of Enhanced electromechanical coupling in SAW resonators based on sputtered non-polar Al0.77Sc0.23N 112¯ thin films

Applied Physics Letters, Mar 9, 2020

Research paper thumbnail of Toward AlGaN Focal Plane Arrays for Solar‐Blind Ultraviolet Detection

Physica Status Solidi A-applications and Materials Science, Dec 29, 2019

Research paper thumbnail of Rayleigh waves in nonpolar Al<sub>0.7</sub>Sc<sub>0.3</sub>N(11 2¯0) films with enhanced electromechanical coupling and quality factor

Applied Physics Letters, Nov 7, 2022

Research paper thumbnail of Effect of V/III ratio and growth pressure on surface and crystal quality of AlN grown on sapphire by metal-organic chemical vapor deposition

Journal of vacuum science & technology, May 1, 2022

Research paper thumbnail of Microstructure and mechanical properties of stress-tailored piezoelectric AlN thin films for electro-acoustic devices

Applied Surface Science, Jun 1, 2017

Research paper thumbnail of An advanced Bragg diffraction imaging technique to characterize defects in SiC and GaN : Topic/category, e.g. AM: Advanced Metrology

Research paper thumbnail of Microstructural and optical emission properties of diamond multiply twinned particles

Journal of Applied Physics, Jan 14, 2020

Research paper thumbnail of Al1−xScxN Thin Films at High Temperatures: Sc-Dependent Instability and Anomalous Thermal Expansion

Micromachines, Aug 8, 2022

Research paper thumbnail of InGaAs infrared detector development for SWIR imaging applications

Proceedings of SPIE, Oct 25, 2013

ABSTRACT We report on materials and technology development for short-wave infrared photodetectors... more ABSTRACT We report on materials and technology development for short-wave infrared photodetectors based on InGaAs p-i-n and avalanche photodiodes (APDs). Using molecular beam epitaxy for the growth of thin layers with abrupt interfaces, which are required for optimized APD structures, excellent crystalline quality has been achieved for detector structures grown on 3-inch InP substrates. For the fabrication of focal plane detector arrays, we employed a mesa etching technology in order to compare the results with the commonly utilized planar technology. Camera detector arrays as well as test structures with various sizes and geometries for materials and process characterization are processed using a dry-etch mesa technology. Aspects of the process development are presented along with measured dark-current and photo-current characteristics of the detector devices.

Research paper thumbnail of Improved AlScN/GaN heterostructures grown by metal-organic chemical vapor deposition

Semiconductor Science and Technology, Jan 22, 2021

AlScN/GaN epitaxial heterostructures have raised much interest in recent years, because of the hi... more AlScN/GaN epitaxial heterostructures have raised much interest in recent years, because of the high potential of such structures for high-frequency and high-power electronic applications. Compared to conventional AlGaN/GaN heterostructures, the high spontaneous and piezoelectric polarization of AlScN can yield to a five-time increase in sheet carrier density of the two-dimensional electron gas formed at the AlScN/GaN heterointerface. Very promising radio-frequency device performance has been shown on samples deposited by molecular beam epitaxy. Recently, AlScN/GaN heterostructures have been demonstrated, which were processed by the more industrial compatible growth method metal-organic chemical vapor deposition (MOCVD). In this work, SiN x passivated MOCVD-grown AlScN/GaN heterostructures with improved structural quality have been developed. Analytical transmission electron microscopy, secondary ion mass spectrometry and high-resolution x-ray diffraction analysis indicate the presence of undefined interfaces between the epitaxial layers and an uneven distribution of Al and Sc in the AlScN layer. However, AlScN-based high-electron-mobility transistors (HEMT) have been fabricated and compared with AlN/GaN HEMTs. The device characteristics of the AlScN-based HEMT are promising, showing a transconductance close to 500 mS mm−1 and a drain current above 1700 mA mm−1.

Research paper thumbnail of Electrothermal Performance of AlGaN/GaN Lateral Transistors with >10 μm Thick GaN Buffer on 200 mm Diameter‐Engineered Substrates

Physica Status Solidi A-applications and Materials Science, Jun 19, 2023

Research paper thumbnail of Reduced non-thermal roll-over in violet-emitting GaInN wide-well LEDs grown on low-dislocation-density substrates

Proceedings of SPIE, Feb 12, 2009

Research paper thumbnail of Absorption and Emission Properties of Light Emitting Diode Structures Containing GaInN/GaN QWs

Acta Physica Polonica A, Nov 1, 2011

Research paper thumbnail of Efficient 350 nm LEDs on low edge threading dislocation density AlGaN buffer layers

Proceedings of SPIE, Feb 10, 2011

Research paper thumbnail of Epitaxial growth of GaInAs/AlGaAsSb quantum cascade lasers

Journal of Crystal Growth, Apr 1, 2007

ABSTRACT

Research paper thumbnail of Current developments for type-II superlattice imaging systems

Proceedings of SPIE, May 13, 2011

InAs/GaSb-based type-II superlattice photodiodes have considerably gained interest as high-perfor... more InAs/GaSb-based type-II superlattice photodiodes have considerably gained interest as high-performance infrared detectors. Beside the excellent properties of InAs/GaSb superlattices, like the relatively high effective electron mass suppressing tunneling currents, the low Auger recombination rate, and a high quantum efficiency, the bandgap can be widely adjusted within the infrared spectral range from 3 - 30 mum depending on the layer thickness

Research paper thumbnail of Plasma affected 2DEG properties on GaN/AlGaN/GaN HEMTs

Physica status solidi, Feb 29, 2012

Research paper thumbnail of Measurement of internal polarization by QCSE induced level shift in AlGaN quantum cascade emitters

IEEE Photonics Technology Letters, 2019

An indirect method to determine the internal polarization of a GaN/AlGaN-based quantum well is pr... more An indirect method to determine the internal polarization of a GaN/AlGaN-based quantum well is presented. The technique consists of carefully measuring the difference between the two lowest conduction subband levels under application of an electrical bias across the epitaxial layers. Due to a quantum confined Stark effect, the bound energy levels of the well show a strong frequency shift which depends on the size of the external field. Since this electric field was oriented oppositely to the internal polarization, partial screening of the latter occurred. By measuring these Stark shifts at three different fields, one was able to calculate the size of the internal polarization. Since the composition of the AlGaN barriers had previously been determined by X-ray diffraction, an extrapolated value of the internal polarization – as it would occur in a pure AlN/GaN interface – could be given. In agreement with the literature, a value of 720 MV/m was found.