The axial C4D (Capacitively Coupled Contactless Conductivity Detection) measurement electronics for capillary electrophoresis is considered and a new improved C5D compensated detection concept is proposed and tested. Using the idle compensation channel with inversed signal and immediate analogue summation of the active and idle channel currents yields effective suppression of the influence of the parasitic stray capacitance. Preliminary experiments have confirmed at least threefold improvements of measurement resolution. Realisation of electronics allows flexible tuning of frequency from 0.2 MHz to 2 MHz. The relatively high voltage supply of 15 V for the AC measurement units together with 24bit accurate analogue-to-digital converter yields additional improvement for the sensitivity.

Influence of barrier material and structure on carrier quantum confinement in GaAsBi quantum wells (QWs) is studied comprehensively. Single- and multi-QW structures were grown using solid-state molecular beam epitaxy with conventional rectangular, step-like and parabolically graded AlGaAs barrier designs. It was discovered that room temperature photoluminescence is increased by more than 50 times in the GaAsBi QWs with parabolically graded barriers (PGBs) if compared to standard rectangular and step-like structures. The enhancement of photoluminescence was reproducible within the range of growth parameters. The carrier localization and increase of trapping efficiency in GaAsBi QWs is responsible for observed enhancement in radiative properties of PGB structures. The random potential field fluctuations for carriers were increased up to 44 meV due to the blurred well-barrier interface causing the conditions for Bi content and/or well width variations. Due to the impact of self-organizing effects on the reproducibility of optical properties, the GaAsBi QWs with AlGaAs PGBs open the window for fabrication of 1.0–1.55 μm wavelength emission lasers based on GaAsBi quantum structures.

Paper discusses some cost-efficient and convenient solutions for the microcontroller-based voltage measurements. Microcontrollers offer several flexible possibilities to modify the reference voltage, to switch between different amplification/attenuation coefficients or to add a necessary bias to the measured voltage. Five unconventional methods are described that have been used in scientific experimental research and/or distant learning toolkits to enhance the accuracy of the built-in analogue to digital converters of ordinary microprocessors.

In this paper, a numerical onedimensional steady-stke analysis of forward-biased diode structures based on direct-gap semiconductors is presented. The model used in this study is based on numerical solution of the set of fundamental equations for semiconductors with boundary conditions on contacts. The continuity equations for electrons and holes are modified to take into account the carrier generation due to band-toband recombination radiation in the n-base and p+-emitter regions. The abrupt junctions in a p +-n-n +-structure and theoretical band-to-band recombination radiation spectra are assumed. Results of calculations on GaAs are given.

The quantum mechanics courses usually do not discuss the transforms between coordinate-and momentum-presentations relevant to the basic quantum well tasks. If we use instead momentum p the wavenumber k=p/ƫ then those transforms are analogous to timedependent versus frequency-dependent transforms in classical signal processing. The paper presents numerical calculations for single and multiple quantum wells. The Heisenberg's uncertainty relation validity is directly checked and the changes in spatial spectra due to increasing periodicity are discussed.