Optical Characterisation of MOVPE Grown Vertically Correlated InAs/GaAs Quantum Dots

Structures with self-organised InAs quantum dots in a GaAs matrix were grown by the low pressure metal-organic vapour phase epitaxy (LP-MOVPE) technique. Photoluminescence in combination with photomodulated reflectance spectroscopy were used as the main characterisation methods for the growth optimisation. Results show that photoreflectance spectroscopy is an excellent tool for characterisation of QD structures wetting layers (thickness and composition) and for identification of spacers in vertically stacked QDs structures.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

AlSb/InAsSb/AlSb deep QWs for the two band high temperature superlinear luminescence

InAlAsSb/GaSb based hetero-nanostructures with deep quantum wells grown on GaSb are promising materials for the optoelectronic devices for near- and mid-IR spectral regions. Optical power and quantum efficiency of the LEDs based on the narrow bandgap semiconductor compounds (InGa)(AsSb) are limited by the nonradiative Auger recombination. Earlier we have proposed a method to increase the optical power in the bulk narrow bandgap and later in GaSb-based nanostructures with a deep QW by the effect of impact ionization on the QW with high band offset

MOVPE GaN/AlGaN HEMT nano-structures

GaN/AlGaN-based high electron mobility transistors (HEMTs) attain better performance than their state-of-the-art full silicon-based counterparts do, offering higher power, higher frequency as well as higher temperature of operation and stability, although their voltage and current limits are somewhat lower than for the SiC-based HEMTs. GaN/AlGaN-based HEMTs are a potential choice for electric-powered vehicles, for which they are approved not only for their power parameters, but also for their good temperature stability, lifetime and reliability. It is important to optimize HEMT structures and their growth parameters to reach the optimum function for the real-world applications. HEMT structures were grown by MOVPE technology in AIXTRON apparatus on (111)-oriented single-surface polished Si substrates. Structural, optical and transport properties of the structures were measured by X-ray diffraction, optical reflectivity, time-resolved photoluminescence and micro-Raman spectroscopy.\

Preparation and characterization of selected optical materials

Crystal structure and technology procedure was optimized to obtained better parameters of PL and RL as well as homogeneity of structure. Structural and optical parameters were measured and evaluated; their influence on crystal characteristics was discussed. New improved material was proposed. P.W = Peak wavelength; P.I = Peak intensity; FWHM = Full With in Half Maximum; D.W = dominant wavelength; I.W = integral w.; I.I = integrated intensity; R.F = reflectivity; T.H = thickness were measured

Growth of semiconducting heterostructures by MOVPE

The lecture focuses on properties, preparation and in-situ characterization of semiconducting heterostructures prepared by MOVPE technology

Microprocessor Tester of Cables

Import 19/10/2011V následující bakalářské práci je popsán tester UTP kabelů včetně problematiky samotných kabelů, popis použitého mikropočítače a displeje. V kostce je popsána funkce samotného zařízení. Dále práce obsahuje algoritmus programu s popisem a názornými ukázkami stavů displeje při jednotlivých krocích, schéma zapojeni testeru a jako příloha je na CD uveden komentovaný výpis programu pro monolitický mikropočítač PIC.In following bachelor thesis is described tester of UTP cables including problems of cables itself, description of used microprocessor and display. In a nutshell is described function of single equipment. Further this thesis includes algorithm of programme with description and graphic sample of display in every single step, wiring diagram of tester and as suplement is added CD with commented statement of programme for monolithic microporcessor PIC.460 - Katedra informatikydobř

General overview of GaN devices and transport properties of AlGaN/GaN HEMT structures - impact of dislocation density and improved design

GaN-based nanostructures are used for many present semiconductor devices. The main topics are structures for blue LEDs and LDs, but there are also other interesting and important GaN devices namely for power electronics, scintillators and detectors as well as High Electron Mobility Transistors (HEMT). Reduction of dislocation density considerably increases electron mobility in 2DEG. All presented results support our expectation that a suitably designed AlGaN back barrier can help to prevent this phenomenon