Dario Schiavon | Polish Academy of Sciences (original) (raw)
Papers by Dario Schiavon
Japanese Journal of Applied Physics, Aug 22, 2018
Micromachines, Feb 9, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Proceedings of SPIE, May 11, 2017
GaN laser diodes fabricated from the AlGaInN material system is an emerging technology for high p... more GaN laser diodes fabricated from the AlGaInN material system is an emerging technology for high power, optical integration and quantum applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well, giving rise to new and novel applications including displays and imaging systems, free-space and underwater telecommunications and the latest quantum technologies such as optical atomic clocks and atom interferometry.
Superlattices and Microstructures, Apr 1, 2018
In this work, we investigate the role of the electron blocking layer (EBL) in laser diodes based ... more In this work, we investigate the role of the electron blocking layer (EBL) in laser diodes based on a graded index separate confinement heterostructure. We compare two sets of devices with very different EBL aluminum composition (3% and 12%) and design (graded and superlattice). The results of electro-optical characterization of these laser diodes reveal surprisingly modest role of electron blocking layer composition in determination of the threshold current and the differential efficiency values. However, EBL structure influences the operating voltage, which is decreased for devices with lower EBL and superlattice EBL. We observe also the differences in the thermal stability of devices e characteristic temperature is lower for lasers with 3% Al in EBL.
Verhandlungen der Deutschen Physikalischen Gesellschaft, 2013
Physica Status Solidi B-basic Solid State Physics, Jan 19, 2012
We investigated lateral charge carrier transport in indium gallium nitride InGaN/GaN multi‐quantu... more We investigated lateral charge carrier transport in indium gallium nitride InGaN/GaN multi‐quantum wells for two different samples, one sample emitting green light at about 510 nm and the other emitting cyan light at about 470 nm. For the cyan light emitting sample we found a diffusion constant of 1.2 cm2/s and for the green light emitting sample 0.25 cm2/s. The large difference in diffusion constant is due to a higher point defect density in the green light emitting quantum wells (QWs) as high indium incorporation tends to reduce material quality.
Physica Status Solidi B-basic Solid State Physics, Feb 1, 2013
Physica Status Solidi B-basic Solid State Physics, Feb 22, 2012
Scientific Reports, Jan 27, 2020
We studied mechanisms of recombination in inGan quantum wells in polar and semipolar structures. ... more We studied mechanisms of recombination in inGan quantum wells in polar and semipolar structures. photoluminescence measurements show that the optical emission linewidths for polar and semipolar structures are almost identical suggesting the same level of indium fluctuations in quanutm wells. Their "peak-energy-versus-temperature" relations demonstrate very pronounced "s-shape" effect. Emission linewidth measured by cathodoluminescence does not depend on area from which the light is collected meaning that the fluctuations are smaller that 100 nm. The time scale of recombination process are of the order of 80 ns for polar and 2 ns for semipolar. Energy dispersion of the recombination time is strong in polar structures and very weak in semipolar ones which can be interperted in terms of electric field influence on photoluminescence lifetime energy dispersion. At room temparture emmission is dominated by Schockley-Hall-Read recombination and does not show any dispersion. Rate equation analysis of photoluminescence transients show domination of excitonic recombination in the case of polar samples (low temperature) and bimolecular in the case of semipolar ones. Both types of quantum wells, polar and semipolar look similar from the point of view of localization but differ in their radiative recombination mechanisms.
Japanese Journal of Applied Physics, Jan 5, 2018
In this work the effect of external electric field on the broadening of optical transitions in a ... more In this work the effect of external electric field on the broadening of optical transitions in a triple polar InGaN/GaN quantum well is studied. Experimental investigation using photoluminescence and electroreflectance show that the reduction of the internal electric field by an external voltage reduces the broadening of the transitions. This is direct evidence that the broadening of photoluminescence in InGaN/GaN quantum wells is enhanced by the built-in electric field. This conclusion is supported by theoretical modelling within the random quantum well model. Additionally, we show that the exciton-phonon coupling can be controlled by an external electric field.
ECS Journal of Solid State Science and Technology, Nov 4, 2019
Applied Physics Letters, Mar 18, 2013
We report on a green light-emitting device, in which the light of an efficient blue 1 mm2 GaInN/G... more We report on a green light-emitting device, in which the light of an efficient blue 1 mm2 GaInN/GaN light-emitting diode (LED) is converted into green light by an optically pumped GaInN/GaN multiple quantum well structure. This solution reached an efficacy of 127 lm/W, i.e., higher than that of state-of-the-art 1 mm2 GaInN/GaN LEDs emitting directly at the target wavelength, at 350 mA current and 535 nm peak wavelength. Optically pumped converters overcome the design limitations of typical multiple quantum well LEDs, where carrier transport issues limit the maximum number of functioning wells and might help to solve the problem of the green gap.
Applied Physics Letters, Mar 9, 2015
The microstructural evolution of InGaN/GaN multiple quantum wells grown by metalorganic chemical ... more The microstructural evolution of InGaN/GaN multiple quantum wells grown by metalorganic chemical vapor phase epitaxy was studied as a function of the growth temperature of the GaN quantum barriers (QBs). We observed the formation of basal stacking faults (BSFs) in GaN QBs grown at low temperature. The presence of BSFs terminated by stacking mismatch boundaries (SMBs) leads to the opening of the structure at the surface into a V-shaped trench loop. This trench may form above an SMB, thereby terminating the BSF, or above a junction between the SMB and a subsequent BSF. Fewer BSFs and thus fewer trench defects were observed in GaN QBs grown at temperatures higher than 830 °C. Further increase in the growth temperature of the GaN QBs led to the suppression of the threading dislocation opening into V-pits.
Optics Express, Jan 19, 2021
Most optoelectronic devices share the same basic epitaxial structure – a stack of quantum wells (... more Most optoelectronic devices share the same basic epitaxial structure – a stack of quantum wells (QWs) sandwiched between p- and n-doped layers. In nitride semiconductors, where holes have 20-times lower mobility than electrons, the holes are able to populate only the topmost 1–2 QWs. The inability to distribute the holes in a large-enough number of QWs is a cause of high Auger recombination in nitride LEDs. Lateral carrier injection is an alternative design, in which the doped regions are situated at the sides of the QW stack and the carriers diffuse horizontally into the QWs. Given that the carriers are injected into all available QWs, it finally makes sense to grow structures with a large number of QWs. We report the results of our computer simulations, which explore the advantages of LCI-based LEDs in terms of energy efficiency.
Quantum technologies containing key GaN laser components will enable a new generation of precisio... more Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the u.v. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for quantum sensors such as optical clocks and cold-atom interferometry systems. This includes the [5s2S1/2-5p2P1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s21S0-5p1P1] cooling transition in neutral strontium clocks at 461 nm and the [5s2s1/2 – 6p2P3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.
Emerging Imaging and Sensing Technologies for Security and Defence VII
Japanese Journal of Applied Physics, Aug 22, 2018
Micromachines, Feb 9, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Proceedings of SPIE, May 11, 2017
GaN laser diodes fabricated from the AlGaInN material system is an emerging technology for high p... more GaN laser diodes fabricated from the AlGaInN material system is an emerging technology for high power, optical integration and quantum applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well, giving rise to new and novel applications including displays and imaging systems, free-space and underwater telecommunications and the latest quantum technologies such as optical atomic clocks and atom interferometry.
Superlattices and Microstructures, Apr 1, 2018
In this work, we investigate the role of the electron blocking layer (EBL) in laser diodes based ... more In this work, we investigate the role of the electron blocking layer (EBL) in laser diodes based on a graded index separate confinement heterostructure. We compare two sets of devices with very different EBL aluminum composition (3% and 12%) and design (graded and superlattice). The results of electro-optical characterization of these laser diodes reveal surprisingly modest role of electron blocking layer composition in determination of the threshold current and the differential efficiency values. However, EBL structure influences the operating voltage, which is decreased for devices with lower EBL and superlattice EBL. We observe also the differences in the thermal stability of devices e characteristic temperature is lower for lasers with 3% Al in EBL.
Verhandlungen der Deutschen Physikalischen Gesellschaft, 2013
Physica Status Solidi B-basic Solid State Physics, Jan 19, 2012
We investigated lateral charge carrier transport in indium gallium nitride InGaN/GaN multi‐quantu... more We investigated lateral charge carrier transport in indium gallium nitride InGaN/GaN multi‐quantum wells for two different samples, one sample emitting green light at about 510 nm and the other emitting cyan light at about 470 nm. For the cyan light emitting sample we found a diffusion constant of 1.2 cm2/s and for the green light emitting sample 0.25 cm2/s. The large difference in diffusion constant is due to a higher point defect density in the green light emitting quantum wells (QWs) as high indium incorporation tends to reduce material quality.
Physica Status Solidi B-basic Solid State Physics, Feb 1, 2013
Physica Status Solidi B-basic Solid State Physics, Feb 22, 2012
Scientific Reports, Jan 27, 2020
We studied mechanisms of recombination in inGan quantum wells in polar and semipolar structures. ... more We studied mechanisms of recombination in inGan quantum wells in polar and semipolar structures. photoluminescence measurements show that the optical emission linewidths for polar and semipolar structures are almost identical suggesting the same level of indium fluctuations in quanutm wells. Their "peak-energy-versus-temperature" relations demonstrate very pronounced "s-shape" effect. Emission linewidth measured by cathodoluminescence does not depend on area from which the light is collected meaning that the fluctuations are smaller that 100 nm. The time scale of recombination process are of the order of 80 ns for polar and 2 ns for semipolar. Energy dispersion of the recombination time is strong in polar structures and very weak in semipolar ones which can be interperted in terms of electric field influence on photoluminescence lifetime energy dispersion. At room temparture emmission is dominated by Schockley-Hall-Read recombination and does not show any dispersion. Rate equation analysis of photoluminescence transients show domination of excitonic recombination in the case of polar samples (low temperature) and bimolecular in the case of semipolar ones. Both types of quantum wells, polar and semipolar look similar from the point of view of localization but differ in their radiative recombination mechanisms.
Japanese Journal of Applied Physics, Jan 5, 2018
In this work the effect of external electric field on the broadening of optical transitions in a ... more In this work the effect of external electric field on the broadening of optical transitions in a triple polar InGaN/GaN quantum well is studied. Experimental investigation using photoluminescence and electroreflectance show that the reduction of the internal electric field by an external voltage reduces the broadening of the transitions. This is direct evidence that the broadening of photoluminescence in InGaN/GaN quantum wells is enhanced by the built-in electric field. This conclusion is supported by theoretical modelling within the random quantum well model. Additionally, we show that the exciton-phonon coupling can be controlled by an external electric field.
ECS Journal of Solid State Science and Technology, Nov 4, 2019
Applied Physics Letters, Mar 18, 2013
We report on a green light-emitting device, in which the light of an efficient blue 1 mm2 GaInN/G... more We report on a green light-emitting device, in which the light of an efficient blue 1 mm2 GaInN/GaN light-emitting diode (LED) is converted into green light by an optically pumped GaInN/GaN multiple quantum well structure. This solution reached an efficacy of 127 lm/W, i.e., higher than that of state-of-the-art 1 mm2 GaInN/GaN LEDs emitting directly at the target wavelength, at 350 mA current and 535 nm peak wavelength. Optically pumped converters overcome the design limitations of typical multiple quantum well LEDs, where carrier transport issues limit the maximum number of functioning wells and might help to solve the problem of the green gap.
Applied Physics Letters, Mar 9, 2015
The microstructural evolution of InGaN/GaN multiple quantum wells grown by metalorganic chemical ... more The microstructural evolution of InGaN/GaN multiple quantum wells grown by metalorganic chemical vapor phase epitaxy was studied as a function of the growth temperature of the GaN quantum barriers (QBs). We observed the formation of basal stacking faults (BSFs) in GaN QBs grown at low temperature. The presence of BSFs terminated by stacking mismatch boundaries (SMBs) leads to the opening of the structure at the surface into a V-shaped trench loop. This trench may form above an SMB, thereby terminating the BSF, or above a junction between the SMB and a subsequent BSF. Fewer BSFs and thus fewer trench defects were observed in GaN QBs grown at temperatures higher than 830 °C. Further increase in the growth temperature of the GaN QBs led to the suppression of the threading dislocation opening into V-pits.
Optics Express, Jan 19, 2021
Most optoelectronic devices share the same basic epitaxial structure – a stack of quantum wells (... more Most optoelectronic devices share the same basic epitaxial structure – a stack of quantum wells (QWs) sandwiched between p- and n-doped layers. In nitride semiconductors, where holes have 20-times lower mobility than electrons, the holes are able to populate only the topmost 1–2 QWs. The inability to distribute the holes in a large-enough number of QWs is a cause of high Auger recombination in nitride LEDs. Lateral carrier injection is an alternative design, in which the doped regions are situated at the sides of the QW stack and the carriers diffuse horizontally into the QWs. Given that the carriers are injected into all available QWs, it finally makes sense to grow structures with a large number of QWs. We report the results of our computer simulations, which explore the advantages of LCI-based LEDs in terms of energy efficiency.
Quantum technologies containing key GaN laser components will enable a new generation of precisio... more Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the u.v. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for quantum sensors such as optical clocks and cold-atom interferometry systems. This includes the [5s2S1/2-5p2P1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s21S0-5p1P1] cooling transition in neutral strontium clocks at 461 nm and the [5s2s1/2 – 6p2P3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.
Emerging Imaging and Sensing Technologies for Security and Defence VII