Low-temperature anti-Stokes photoluminescence in CdSe/ZnSe nanostructures

Intense anti-Stokes photoluminescence was observed at low temperatures in CdSe/ZnSe nanostructures with separate CdSe inserts in a ZnSe matrix; the nominal thickness of these inserts amounted to 1.5 and 0.6 monolayers. It is shown that the intensity of an anti-Stokes band excited by the photons of energies considerably lower than the band’s peak is quadratic in the excitation power; in the case of resonance excitation, a weaker dependence is obtained. A mechanism behind the excitation of anti-Stokes photoluminescence is suggested on the basis of nonlinear two-step two-photon absorption via the deep states of the defect centers including cation vacancies localized at the barrier-nanoisland interface.     

Specific features of the transport properties of the Lu<Subscript>0.1</Subscript>Bi<Subscript>1.9</Subscript>Te<Subscript>3</Subscript> compound

The temperature and electric- and magnetic-field dependences of the resistivity of the R_0.1Bi_1.9Te₃ compound are investigated. It is shown that, in the low-temperature region, variable-range hopping conductivity is realized in this compound. In the temperature range of hopping conductivity, the electrical resistivity decreases with increasing electric-field strength in the sample, which is typical of charge-carrier tunneling from one localized state in the impurity band to another. Investigation of the transverse magnetoresistance revealed the crossover from the parabolic dependence of the magnetoresistance in low fields to the linear dependence in high fields. The established features of the transport properties of the R_0.1Bi_1.9Te₃ compound are characteristic of inhomogeneous and disordered semiconductors.     

On the Concatenated Code Constructions for Slotted Multiuser Communication Channel

Journal of Communications Technology and Electronics - In this paper we investigate a multiuser vector-disjunctive channel where users transmit binary vectors of length $$L$$ . Previously the...     

Promotion of metallurgical reactions at the Ni-SiC interface by irradiation with protons

It is shown that irradiation of Ni-SiC structures with protons at elevated temperatures promotes metallurgical reactions at the Ni-SiC interface owing to a diffusion mechanism stimulated by the generation of radiation defects. The most pronounced effect of mixing at the metal-semiconductor interface is observed if the thickness of the metal film is equal to the projected range of protons.     

Three-Dimensional FDTD Simulation of Micro-Pillar Microcavity Geometries Suitable for Efficient Single-Photon Sources

We present the results of calculations of the microcavity mode structure of distributed-Bragg-reflector (DBR) micro-pillar microcavities of group III-V semiconductor materials. These structures are suitable for making single photon sources when a single quantum dot is located at the center of a wavelength scale cavity. The 3-D finite difference time domain (FDTD) method is our primary simulation tool and results are validated against semi-analytic models. We show that high light extraction efficiencies can be achieved (>90%) limited by sidewall scattering and leakage. Using radial trench DBR microcavities or 2-D photonic crystal structures, we can further suppress sidewall emission, however, light is then redirected into other leaky modes     

On the Spatial Localization of Free Electrons in 4<Emphasis Type="Italic">H</Emphasis>-SiC MOSFETS with an <Emphasis Type="Italic">n</Emphasis> Channel

The problem of the spatial localization of free electrons in 4H-SiC metal—oxide—semiconductor field effect transistors (MOSFETS) with an accumulation- and inversion-type n channel is theoretically analyzed. The analysis demonstrates that, in optimally designed accumulation transistors (ACCUFETs), the average distance from the surface, at which free electrons are localized, may be an order of magnitude larger than that in inversion MOSFETs. This can make 4H-SiC ACCUFETs advantageous as regards the effective carrier mobility in a conducting channel.     

Structural and optical properties of thin In2O3 films produced by autowave oxidation

Cubic-phase In₂O₃ films are produced by the autowave oxidation reaction. Electron microscopy and photoelectron spectroscopy of the atomic profiles show that the samples are homogeneous over the entire area and throughout the thickness, with the typical grain size being 20–40 nm. The optical and electrical properties are studied for In₂O₃ films fabricated at different pressures in the vacuum chamber. In the wave-length range from 400 to 1100 nm, the transparency of the films was higher than 85%; the resistivity of the films was 1.8 × 10^?2 Ω cm.     

Effect of electron and proton irradiation on characteristics of SiC surface-barrier detectors of nuclear radiation

Structures with a Schottky barrier based on CVD-grown 4H-SiC films were irradiated with 8 MeV protons and 900 keV electrons. The maximum fluences were 10¹⁴ and 3 × 10¹⁶ cm^?2, respectively. It was found that, in the case of electrons, the primarily introduced radiation defects are closely spaced Frenkel pairs. Changes in the electrical characteristics of the structures were compared. Capacitance methods and nuclear spectrometry were employed. The latter technique was used to determine the charge collection efficiency under pulsed ionization with α-particles. It was determined that, under proton irradiation, the charge collection efficiency steadily decreases as the fluence increases. For electrons, the efficiency remains unchanged in the fluence range (1–3) × 10¹⁶ cm^?2. However, a fluence of 3 × 10¹⁶ cm^?2 leads to a pronounced increase in the non-uniformity of charge transport conditions throughout the sample volume.     

Anomalous electron spin splitting in InAs pumped by injection

The electroluminescence and photoluminescence of bulk n-InAs with a high concentration of donors (N _d ≈ 5 × 10¹⁶ cm^?3) is studied experimentally in magnetic field in the Faraday layout of the experiment. Under the conditions of electrical injection, the photon energy corresponding to the electroluminescence peak exceeds the energy band gap E _g. When a magnetic field is applied, the energy of the peak becomes lower than E _g, and the peak splits into two circular-polarized components. The splitting depends on the injection current. In moderate magnetic fields (about 2 T), the splitting can be much more profound than the calculated splitting corresponding to the well-known g factor of electrons in InAs. The effect is attributed to different degrees of magnetic freezing-out of electrons with different spin orientation. The maximum in the dependence of the degree of polarization of photoluminescence on the magnetic field and the behavior of the photoluminescence line width support the model suggested.     

A 100-dB CMRR CMOS Operational Amplifier With Single-Supply Capability

A CMOS operational amplifier that has a common-mode rejection ratio (CMRR), a power-supply rejection ratio (PSRR), and gain above 100 dB for each of these parameters is described. This is achieved by combining a high output-impedance tail current source with a stable drain-source voltage of the input transistors. The common-mode input signal range includes the negative rail. This is obtained by controlling the bulk bias of the input and cascoding transistors. The amplifier consists of two gain stages connected via cascoded current mirrors. The gain is improved by using gain boost in the current mirrors, and by the suppression of impact ionization current in the output stage