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Material Characterization and Modeling of Interband Cascade Light Emitting Diodes
Herzánová, Kristína ; Bastard, Gérald (oponent) ; Detz, Hermann (vedoucí práce)
This thesis focuses on the material and loss characterization of heterostructures used in interband cascade devices and the modeling of interband cascade light-emitting devices (ICLEDs). Interband cascade devices, particularly lasers and light-emitting diodes, are critical for mid-infrared photonic applications due to their efficient operation and potential for integration into photonic circuits. The study involves extracting material parameters from spectroscopic ellipsometry and FTIR measurements, and extending an existing transport model to account for radiative recombination processes, specifically the spontaneous emission in ICLEDs. Among the different loss mechanisms in these devices, particular attention was given to the valence intersubband absorption, which degrades the operation of interband cascade devices in the mid-infrared wavelength region above 4 m. The results, obtained through experimental characterization of interband cascade laser (ICL) waveguides examining their transmission losses, demonstrated the impact of valence intersubband absorption under various operating conditions. This research contributes to the optimization of interband cascade structures, leading to enhanced performance and broader applicability in sensing, environmental monitoring, and biomedical diagnostics.
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Detection of DNA/RNA fragments using graphene sensor and influence of upper electrolytic gate
Herzánová, Kristína ; Konečný, Martin (oponent) ; Bartošík, Miroslav (vedoucí práce)
Graphene's unique properties, such as biocompatibility, high charge carrier mobility and surface sensitivity, make it a suitable material for biosensing devices. This thesis aims to describe and demonstrate such sensors and the measurements performed to detect fragments of DNA, specifically cytosine-based substances. The graphene is employed in field-effect transistors as the conductive sensing channel. The doping of graphene induced by adsorbed molecules on the channel causes changes in graphene's transport properties. These changes are reflected in electronic response measurements: real-time measurements of graphene sheet resistance responding to the addition of different solutions and dependency of the resistance on the continual change of gate voltage. The latter can be performed either in the back-gated or electrolytic top-gated configuration of the FET sensor. The difference between the two configurations is observed, as well as the effect of the distance between graphene and top-gate electrode on the sensor response. The output of these measurements are transfer curves exhibiting typical peaks indicating the charge neutrality point (Dirac point) of graphene. Different concentrations of the analyte solution results in different shift of the Dirac point voltage, quantifying the doping level.
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Detection of DNA/RNA fragments using graphene sensor and influence of upper electrolytic gate
Herzánová, Kristína ; Konečný, Martin (oponent) ; Bartošík, Miroslav (vedoucí práce)
Graphene's unique properties, such as biocompatibility, high charge carrier mobility and surface sensitivity, make it a suitable material for biosensing devices. This thesis aims to describe and demonstrate such sensors and the measurements performed to detect fragments of DNA, specifically cytosine-based substances. The graphene is employed in field-effect transistors as the conductive sensing channel. The doping of graphene induced by adsorbed molecules on the channel causes changes in graphene's transport properties. These changes are reflected in electronic response measurements: real-time measurements of graphene sheet resistance responding to the addition of different solutions and dependency of the resistance on the continual change of gate voltage. The latter can be performed either in the back-gated or electrolytic top-gated configuration of the FET sensor. The difference between the two configurations is observed, as well as the effect of the distance between graphene and top-gate electrode on the sensor response. The output of these measurements are transfer curves exhibiting typical peaks indicating the charge neutrality point (Dirac point) of graphene. Different concentrations of the analyte solution results in different shift of the Dirac point voltage, quantifying the doping level.
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