Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998705
S. Fox, S. Lis, S. E. J. Q'Kane, D. Allsopp, J. Sarma
In the work reported here we use the finite-difference time-domain method to model an ordered nanorod array incorporated in a vertical LED structure in place of the surface roughened region. The simulations reveal that diffraction dominates the far field emission when the emissive layer lies below the nanorod array, as might occur in a vertical LED structure with the NR layer used as a light extracting element in place of a roughened surface.
{"title":"Influence of geometry on the directionality of light emission of nanorod array vertical light emitting diodes","authors":"S. Fox, S. Lis, S. E. J. Q'Kane, D. Allsopp, J. Sarma","doi":"10.1109/ASDAM.2014.6998705","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998705","url":null,"abstract":"In the work reported here we use the finite-difference time-domain method to model an ordered nanorod array incorporated in a vertical LED structure in place of the surface roughened region. The simulations reveal that diffraction dominates the far field emission when the emissive layer lies below the nanorod array, as might occur in a vertical LED structure with the NR layer used as a light extracting element in place of a roughened surface.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115768169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998706
D. Schmidmayr, J. Zehetner, P. Amann
In order to further improve the efficiency and the spectral quality of white-light LEDs new colour conversion materials which allow a selective and narrow banded conversion of the blue excitation light are needed. Quantum dots could be promising in this regard as they exhibit exactly these properties. For commercially used light sources a stable colour distribution has to be ensured over the entire lifetime. Our experiments revealed a very different degradation characteristic of phosphor and quantum dots. In this paper we present the results of different experiments which aim on the understanding of the mechanism for optical stability. We focused mainly on two degradation effects, a decrease of the photoluminescence intensity and a shift of the emission peak wavelength towards the blue.
{"title":"Investigation of optical stability issues with embedded semiconductor quantum dots used as colour conversion material in LED lighting applications","authors":"D. Schmidmayr, J. Zehetner, P. Amann","doi":"10.1109/ASDAM.2014.6998706","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998706","url":null,"abstract":"In order to further improve the efficiency and the spectral quality of white-light LEDs new colour conversion materials which allow a selective and narrow banded conversion of the blue excitation light are needed. Quantum dots could be promising in this regard as they exhibit exactly these properties. For commercially used light sources a stable colour distribution has to be ensured over the entire lifetime. Our experiments revealed a very different degradation characteristic of phosphor and quantum dots. In this paper we present the results of different experiments which aim on the understanding of the mechanism for optical stability. We focused mainly on two degradation effects, a decrease of the photoluminescence intensity and a shift of the emission peak wavelength towards the blue.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130849456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998712
A. Sanginario, G. Schropfer, S. Zerbini, M. Ekwinska, R. Houlihan, D. Demarchi
The design of a heterogeneous smart system is a major and multidisciplinary challenge. The next generation smart systems will include analog, digital and MEMS components described using different languages relying on parametric models at different abstraction level. The SMArt system Co-design (SMAC) FP7 ICT project aim is the overcome all the issues related to the mixed design of a smart system. Inside this project a step toward design tool integration has been made with the presented work. As a matter of fact, we present a case study for the definition of a complete flow for the design and use of MEMS devices inside standard microelectronics design tools.
{"title":"A MEMS design methodology for model-order-reduction, based on high-order parametric elements","authors":"A. Sanginario, G. Schropfer, S. Zerbini, M. Ekwinska, R. Houlihan, D. Demarchi","doi":"10.1109/ASDAM.2014.6998712","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998712","url":null,"abstract":"The design of a heterogeneous smart system is a major and multidisciplinary challenge. The next generation smart systems will include analog, digital and MEMS components described using different languages relying on parametric models at different abstraction level. The SMArt system Co-design (SMAC) FP7 ICT project aim is the overcome all the issues related to the mixed design of a smart system. Inside this project a step toward design tool integration has been made with the presented work. As a matter of fact, we present a case study for the definition of a complete flow for the design and use of MEMS devices inside standard microelectronics design tools.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114952107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998648
M. Ševčík, M. Husák
This paper shows determination of elastic constants of thin layers deposited on substrates. Resonant ultrasound spectroscopy is used to measure resonant spectras before and after layer deposition. These two spectra are compared and changes in the position of the resonant peaks are associated with layer properties. For thin layers either the elastic moduli or the surface mass density can be determined, providing the complementary information.
{"title":"Determination of elastic properties of surface layers and coatings","authors":"M. Ševčík, M. Husák","doi":"10.1109/ASDAM.2014.6998648","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998648","url":null,"abstract":"This paper shows determination of elastic constants of thin layers deposited on substrates. Resonant ultrasound spectroscopy is used to measure resonant spectras before and after layer deposition. These two spectra are compared and changes in the position of the resonant peaks are associated with layer properties. For thin layers either the elastic moduli or the surface mass density can be determined, providing the complementary information.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129111574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998674
J. Racko, R. Granzner, P. Benko, M. Mikolasek, L. Harmatha, M. Kittler, F. Schwierz, J. Breza
We present a new model of two coupled defect-level recombination. Calculation of the generation and recombination rates is based on the so-called exchange times. These allow calculating the occupation probability of the trapping centres and subsequently the generation-recombination rates of free charge carriers appearing in the continuity equations. Each of these two coupled defect levels has its specific trap density, position in the forbidden band and capture cross-section obtained from DLTS measurements.
{"title":"Model of coupled defect level recombination with participation of multiphonons","authors":"J. Racko, R. Granzner, P. Benko, M. Mikolasek, L. Harmatha, M. Kittler, F. Schwierz, J. Breza","doi":"10.1109/ASDAM.2014.6998674","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998674","url":null,"abstract":"We present a new model of two coupled defect-level recombination. Calculation of the generation and recombination rates is based on the so-called exchange times. These allow calculating the occupation probability of the trapping centres and subsequently the generation-recombination rates of free charge carriers appearing in the continuity equations. Each of these two coupled defect levels has its specific trap density, position in the forbidden band and capture cross-section obtained from DLTS measurements.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130516858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998651
M. Wośko, B. Paszkiewicz, T. Szymański, R. Paszkiewicz
A 2 μm crack-free AlGaN/AlN/GaN heterostructure stack was successfully grown on 2-inch Si(111) substrates by metal organic chemical vapor deposition with high temperature AlN nucleation layer and low temperature AlN interlayer. This approach of GaN buffer deposition on silicon substrate was compared with another ones, utilizing graded AlGaN and super lattice AlN/GaN buffers. The electron mobility of two-dimensional electron gas of AlGaN/AlN/GaN/Si(111) heterostructure measured by impedance spectroscopy was 2080 m2V-1s-1 compared to 2415 m2V-1S-1 obtained for reference AlGaN/AlN/GaN/sapphire heterostructure.
{"title":"Different buffer approaches for AlGaN/GaN heterostructures epitaxy on Si(111) substrates","authors":"M. Wośko, B. Paszkiewicz, T. Szymański, R. Paszkiewicz","doi":"10.1109/ASDAM.2014.6998651","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998651","url":null,"abstract":"A 2 μm crack-free AlGaN/AlN/GaN heterostructure stack was successfully grown on 2-inch Si(111) substrates by metal organic chemical vapor deposition with high temperature AlN nucleation layer and low temperature AlN interlayer. This approach of GaN buffer deposition on silicon substrate was compared with another ones, utilizing graded AlGaN and super lattice AlN/GaN buffers. The electron mobility of two-dimensional electron gas of AlGaN/AlN/GaN/Si(111) heterostructure measured by impedance spectroscopy was 2080 m<sup>2</sup>V<sup>-1</sup>s<sup>-1</sup> compared to 2415 m<sup>2</sup>V<sup>-1</sup>S<sup>-1</sup> obtained for reference AlGaN/AlN/GaN/sapphire heterostructure.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127645490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998713
D. He, C. Liu, D. Trachanis, J. Hese, D. Drogoudis, F. Fummi, F. Stefanni, V. Guamieri, S. Morgan, B. Hayes-Gill
An optical CMOS heart rate sensor that processes the photoplethysmographic signal was designed and fabricated in Austriamicrosystems 0.35μm CMOS process. The sensor consists of photodiode, transimpedance amplifier, analogue bandpass filters, analogue-to-digital converters, digital signal processor, and a timing circuit that is used to modulate the external light-emitting diodes. The mixed-signal simulation has been carried out to validate the system design. With modulated green light source and integrated lock-in detection the sensor is capable of extracting clean photoplethysmographic signal when it is operated in reflectance mode. The heart rate output was compared with commercial devices and they show a good agreement. The chip-level integration enables a small foot print of the design and makes it suitable for the applications of ambulatory monitoring.
{"title":"Design and simulation of an integrated optical CMOS heart rate sensor","authors":"D. He, C. Liu, D. Trachanis, J. Hese, D. Drogoudis, F. Fummi, F. Stefanni, V. Guamieri, S. Morgan, B. Hayes-Gill","doi":"10.1109/ASDAM.2014.6998713","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998713","url":null,"abstract":"An optical CMOS heart rate sensor that processes the photoplethysmographic signal was designed and fabricated in Austriamicrosystems 0.35μm CMOS process. The sensor consists of photodiode, transimpedance amplifier, analogue bandpass filters, analogue-to-digital converters, digital signal processor, and a timing circuit that is used to modulate the external light-emitting diodes. The mixed-signal simulation has been carried out to validate the system design. With modulated green light source and integrated lock-in detection the sensor is capable of extracting clean photoplethysmographic signal when it is operated in reflectance mode. The heart rate output was compared with commercial devices and they show a good agreement. The chip-level integration enables a small foot print of the design and makes it suitable for the applications of ambulatory monitoring.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121679275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998673
J. Foit, M. Husák
In many sensor applications, the frequency variations of signals generated as sustained oscillations are used as a measure of the tracked non-electrical quantity. The variations of oscillation frequency are usually obtained by some mechanism influencing the imaginary parts of impedances constituting a resonant circuit, electrical or some electro-mechanical equivalent. Unfortunately, in all these cases, real parts of the resonant circuit are varied as well, frequently to a quite considerable degree, meaning that in real operation the dynamic impedance of the resonator varies notably. As a result, it is rather difficult to keep the oscillations-generating circuit (i.e., oscillator) operating in optimum mode. In this connection, the optimum operating mode is defined as the state in which the condition for sustained self-oscillation is just fulfilled, without overdriving any of the active and passive devices involved. This paper discusses methods for solving this problem.
{"title":"Special purpose oscillators","authors":"J. Foit, M. Husák","doi":"10.1109/ASDAM.2014.6998673","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998673","url":null,"abstract":"In many sensor applications, the frequency variations of signals generated as sustained oscillations are used as a measure of the tracked non-electrical quantity. The variations of oscillation frequency are usually obtained by some mechanism influencing the imaginary parts of impedances constituting a resonant circuit, electrical or some electro-mechanical equivalent. Unfortunately, in all these cases, real parts of the resonant circuit are varied as well, frequently to a quite considerable degree, meaning that in real operation the dynamic impedance of the resonator varies notably. As a result, it is rather difficult to keep the oscillations-generating circuit (i.e., oscillator) operating in optimum mode. In this connection, the optimum operating mode is defined as the state in which the condition for sustained self-oscillation is just fulfilled, without overdriving any of the active and passive devices involved. This paper discusses methods for solving this problem.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125182269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998707
M. Marso, M. Mikulics, A. Winden, Y. Arango, A. Schafer, Zdenek Sofer, D. Grutzmacher, H. Hardtdegen
Vertically integrated III-nitride nano-LEDs designed for operation in the telecommunication-wavelength range were fabricated and tested in the (p-GaN/InGaN/n-GaN/sapphire) material system. We found that the band edge luminescence energy of the nano-LEDs could be engineered by their size and by the strain interaction with the masked SiO2/GaN substrates; it depends linearly on the structure size. The results of reliability measurements prove that our technological process is perfectly suited for long-term operation of the LEDs without any indication of degradation effects. The presented technology shows strong potential for future low energy consumption optoelectronics.
{"title":"InGaN nano-LEDs for energy saving optoelectronics","authors":"M. Marso, M. Mikulics, A. Winden, Y. Arango, A. Schafer, Zdenek Sofer, D. Grutzmacher, H. Hardtdegen","doi":"10.1109/ASDAM.2014.6998707","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998707","url":null,"abstract":"Vertically integrated III-nitride nano-LEDs designed for operation in the telecommunication-wavelength range were fabricated and tested in the (p-GaN/InGaN/n-GaN/sapphire) material system. We found that the band edge luminescence energy of the nano-LEDs could be engineered by their size and by the strain interaction with the masked SiO2/GaN substrates; it depends linearly on the structure size. The results of reliability measurements prove that our technological process is perfectly suited for long-term operation of the LEDs without any indication of degradation effects. The presented technology shows strong potential for future low energy consumption optoelectronics.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113967253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-12-29DOI: 10.1109/ASDAM.2014.6998657
M. Alsharef, R. Granzner, E. Ture, R. Quay, J. Racko, J. Breza, F. Schwierz
The operation of GaN tri-gate HEMTs is investigated by numerical device simulations. It is shown that the threshold voltage of such structures strongly depends on the width of the AlGaN/GaN body and to a lesser extent on the body height. The body height becomes more important as the gate length is reduced. However, the beneficial effect of the side gates saturates at body heights around 100 nm, independent of the gate length.
{"title":"Design of GaN tri-gate HEMTs","authors":"M. Alsharef, R. Granzner, E. Ture, R. Quay, J. Racko, J. Breza, F. Schwierz","doi":"10.1109/ASDAM.2014.6998657","DOIUrl":"https://doi.org/10.1109/ASDAM.2014.6998657","url":null,"abstract":"The operation of GaN tri-gate HEMTs is investigated by numerical device simulations. It is shown that the threshold voltage of such structures strongly depends on the width of the AlGaN/GaN body and to a lesser extent on the body height. The body height becomes more important as the gate length is reduced. However, the beneficial effect of the side gates saturates at body heights around 100 nm, independent of the gate length.","PeriodicalId":313866,"journal":{"name":"The Tenth International Conference on Advanced Semiconductor Devices and Microsystems","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131555790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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