Determination of the electron concentration and mobility in the vicinity of a quantum well and δ-doped layer in InGaAs/GaAs heterostructures

Comparative admittance measurements in mesadiodes on an n ⁺-GaAs substrate and in ring planar diode structures on an i-GaAs substrate, which contain a Si ??-doped layer and an InGaAs quantum well in the GaAs epitaxial layer are performed. The possibility of determining the concentration profile and electron mobility in the vicinity of the ??-doped layer and the InGaAs quantum well is shown based on an analysis of the simultaneously measured capacitance-voltage and conductance-voltage characteristics of the mesadiodes. By performing such measurements for i-GaAs-based ring diode structures with the given geometry, it is possible to reliably determine only the concentration profile. The influence of the relative location of the quantum well and ??-doped layer on the concentration profile and mobility is revealed. The phenomenon of Maxwell relaxation in i-GaAs-based ring diode structures is discussed.     

Theoretical analysis of surface mountable triple-mode ceramic cavity

A novel surface-mountable ceramic cavity has been considered. The high-permittivity ceramic filling of the basic triple-mode waveguide cavity makes the proposed structure physically small. Integrated microstrip to ceramic filled waveguide transitions provide effective coupling between ceramic cavity and planar circuit. A key point of the suggested theory consists of utilization of weighted Gegenbauer polynomials as the basis functions for the Galerkin's procedure. Such a choice of basis functions guarantees high accuracy and efficiency for the entire simulation algorithm. As an application example, a three-pole L-band filter with advanced high-quality factor is demonstrated.     

Effect of the electrochemical modification of a thin Ga(In)As cap layer on the energy spectrum of InAs/GaAs quantum dots

It was shown that the selective etching and anodic oxidation of a thin Ga(In)As cap layer makes it possible to decrease the ground-state transition energy in InAs/GaAs quantum dots from ～0.9 to ～0.7 eV due to the resulting partial stress relaxation. Similar processing of surface quantum dots leads to a decrease in the quantum-dot height that increases the transition energy.     

Amperometric/potentiometric hydrocarbon sensors: real world solutions for use in ultra high vacuum

Carbonaceous deposits produced on Ru-capped multilayer mirrors under extreme ultra violet irradiation in the presence of adventitious gaseous hydrocarbons are a major obstacle to process implementation of EUV lithography. Here, by means of synchrotron radiation and laboratory measurements we show how carbon contamination occurs as a result of photoelectron-induced surface chemistry. We also demonstrate how a device based on an oxygen ion conducting solid electrolyte can act as a sensitive and reproducible sensor for detection of trace amounts of hydrocarbons in high vacuum environments.     

Long-range effect of the irradiation of silicon with light on the Schottky-barrier photovoltage

It is established that the Schottky-barrier photovoltage decreases as a result of the irradiation of a silicon sample with a barrier by light (incident on the base side). The value of the photovoltage is restored approximately 0.5 h after irradiation. The changes in the photovoltage after irradiation are compared to the behavior of the silicon microhardness and interpreted on the basis of the concept of point defect generation in the long-range effect.     

Effect of hydrogen on the properties of Pd/GaAs/InGaAs diode structures with quantum wells

The effect of hydrogen on photoelectric properties and photoluminescence of Pd/GaAs/InGaAs diode structures with quantum wells (QWs) was investigated. The dependence of the structure characteristics on the thickness of the GaAs anodic oxide layer is revealed, and the optimum oxide thickness for the fabrication of hydrogen sensors is determined. It is established that the existence of metal bridges in a thin oxide layer has a significant influence on the I-V curves of the structures. It is shown that the presence of QWs leads to an increase in the structure’s sensitivity to hydrogen. Using the QWs as local defect probes, formation of the defects resulting from the deposition of a Pd electrode both on natural and on anodized GaAs surface is studied. It is found that defects in the QWs of the diode structures can be passivated by introduction of atomic hydrogen through the Pd electrode upon exposure of the structures to an atmosphere of molecular hydrogen.     

Test results of HTS dipole

Test of HTS dipole with coil wound by Bi-2223 tape was carried out. Volt-current characteristics of the dipole at various temperatures as well as results of magnetic field measurements are presented. A process of transition to normal state for the HTS coil was calculated.     

Electrical and photoelectric properties of Si-based metal–insulator–semiconductor structures with Au nanoparticles at the insulator–semiconductor interface

It is shown that the formation of Au nanoparticles at the insulator–silicon interface in structures with a high density of surface states results in a shift of the Fermi-level pinning energy at this interface towards the valence-band ceiling in silicon and in increasing the surface-state density at energies close to the Fermi level. In this case, a band with a peak at 0.85 eV arises on the photosensivity curves of the capacitor photovoltage, which is explained by the photoemission of electrons from the formed Au-nanoparticle electron states near the valence-band ceiling in silicon.