High-efficiency LEDs based on <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">p</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb/<Emphasis Type="Italic">P</Emphasis>-AlGaAsSb type-II thyristor heterostructures

A new type of light-emitting diodes (LEDs), a high-efficiency device based on an n-GaSb/p-GaSb/n-GaInAsSb/P-AlGaAsSb thyristor heterostructure, with the maximum emission intensity at wavelength λ = 1.95 μm, has been suggested and its electrical and luminescent characteristics have been studied. It is shown that the effective radiative recombination in the thyristor structure in the n-type GaInAsSb active region is provided by double-sided injection of holes from the neighboring p-type regions. The maximum internal quantum efficiency of 77% was achieved in the structure under study in the pulsed mode. The average optical power was as high as 2.5 mW, and the peak power in the pulsed mode was 71 mW, which exceeded by a factor of 2.9 the power obtained with a standard n-GaSb/n-GaInAsSb/P-AlGaAsSb LED operating in the same spectral range. The approach suggested will make it possible to improve LED parameters in the entire mid-IR spectral range (2–5 μm).     

Temperature dependence of the band structure of 3<Emphasis Type="Italic">C</Emphasis>, 2<Emphasis Type="Italic">H</Emphasis>, 4<Emphasis Type="Italic">H</Emphasis>, and 6<Emphasis Type="Italic">H</Emphasis> SiC polytypes

The temperature dependences of significant energy extrema at the high-symmetry points Γ, X, L, K, M, A, and H of the Brillouin zone in the cubic and hexagonal modifications of SiC, as well as the energies of the main interband transitions at these points, were calculated for the first time by the empirical-pseudopotential method. The effect of the temperature dependence of the electron-phonon interaction on the crystal band structure was taken into account via the Debye-Waller factors, and the contribution of the linear expansion of the lattice was accounted for via the temperature dependence of the linear-expansion coefficient. The special features of the temperature dependences of the energy levels and of energies of the interband and intraband transitions are analyzed in detail. The results of the calculations are in good agreement with the known experimental data on the characteristics of SiC-based p-n structures operating in the breakdown mode. For example, the temperature coefficient of the energy of the X_1c–X_3c transition, which is responsible for the narrow violet band in the breakdown-electroluminescence spectra of reverse-biased p-n junctions, was found to be significantly smaller than the temperature coefficients for the interband transitions (from the conduction to valence band). This fact is quite consistent with the experimental curve of the temperature coefficient of the emission spectrum, which has a minimum in the same wavelength range.     

Light-Harvesting in <Emphasis Type="Italic">n</Emphasis>-ZnO/<Emphasis Type="Italic">p</Emphasis>-Silicon Heterojunctions

Zinc oxide (ZnO) films were deposited onto Si to form n-ZnO/p-Si heterojunctions. Under the illumination of by both ultraviolet (UV) light and sunlight, obvious photovoltaic behavior was observed. It was found that the conversion efficiency of the heterojunctions increased significantly with increasing thickness of the ZnO film, and the mechanism for light-harvesting in the heterojunctions is discussed. The results suggest that ZnO films may be helpful to increasing the harvesting of UV photons, thus decreasing the thermalization loss of UV energy in Si-based solar cells.     

Electrical properties of <Emphasis Type="Italic">n</Emphasis>-ZnO/<Emphasis Type="Italic">p</Emphasis>-CuO heterostructures

The n-ZnO/p-CuO heterostructure is prepared, and its I-V characteristic is measured. It is shown that the heterostructure conductivity is primarily determined by the CuO layer and the n-ZnO/p-CuO heterojunction itself.     

Features of high-temperature electroluminescence in an LED <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-InGaAsSb/<Emphasis Type="Italic">p</Emphasis>-AlGaAsSb heterostructure with high potential barriers

The electroluminescent properties of a light-emitting diode n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with high potential barriers are studied in the temperature range of 290–470 K. An atypical temperature increase in the power of the long-wavelength luminescence band with an energy of 0.3 eV is experimentally observed. As the temperature increases to 470 K, the optical radiation power increases by a factor of 1.5–2. To explain the extraordinary temperature dependence of the radiation power, the recombination and carrier transport processes are theoretically analyzed in the heterostructure under study.     

Thin-film polycrystalline <Emphasis Type="Italic">n</Emphasis>-ZnO/<Emphasis Type="Italic">p</Emphasis>-CuO heterojunction

Results of X-ray diffraction and spectral-optical studies of n-ZnO and p-CuO films deposited by gas-discharge sputtering with subsequent annealing are presented. It is shown that, despite the difference in the crystal systems, the polycrystallinity of n-ZnO and p-CuO films enables fabrication of a heterojunction from this pair of materials.     

Electrical Breakdown in Pure <Emphasis Type="Italic">n</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-Si

The results of calculations of the dependences of the kinetic coefficients of impact ionization and thermal recombination on an electric field in pure silicon are presented. By analogy with germanium, the dependences of the breakdown field Е_br on the material compensation ratio K are calculated. The validity of such calculation is justified in detail. The Е_br(K) curves are presented and compared with experimental data in the weak-compensation region. Matching with experimental results at which satisfactory agreement between theory and experiment is observed is performed.     

High-temperature nuclear-detector arrays based on 4 <Emphasis Type="Italic">H</Emphasis>-SiC ion-implantation-doped <Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript>-<Emphasis Type="Italic">n</Emphasis> junctions

Results obtained in a study of spectrometric characteristics of arrays of four detectors based on 4H-SiC ion-implantation-doped p ⁺-n junctions in the temperature range 25–140 °C are reported for the first time. The junctions were fabricated by ion implantation of aluminum into epitaxial 4H-SiC layers of thickness ≤45 μm, grown by chemical vapor deposition with uncompensated donor concentration N _d ? N _a = (4–6) × 10¹⁴ cm^?3. The structural features of the ion-implantation-doped p ⁺-layers were studied by secondary-ion mass spectrometry, transmission electron microscopy, and Rutherford backscattering spectroscopy in the channeling mode. Parameters of the diode arrays were determined by testing in air with natural-decay alpha particles with an energy of 3.76 MeV. The previously obtained data for similar single detectors were experimentally confirmed: the basic characteristics of the detector arrays, the charge collection efficiency and energy resolution, are improved as the working temperature increases.     

Photovoltaic poperties of <Emphasis Type="Italic">n</Emphasis>-ZnO:Al/PbPc/<Emphasis Type="Italic">p</Emphasis>-Si structures

n-ZnO:Al/PbPc/p-Si photosensitive structures are fabricated for the first time. The steady-state current-voltage characteristics and spectral dependences of the relative quantum efficiency of the photoconversion of these structures are studied, and the mechanisms of charge transport and the photosensitivity processes are discussed. It is concluded that they are promising for application as multiband photoconverters of natural light.     

Recombination of charge carriers in the GaAs-based <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">i</Emphasis>-<Emphasis Type="Italic">n</Emphasis> diode

It is established that the radiative recombination of charge carriers plays a substantial role in the GaAs-based p-i-n diodes at high densities of the forward current. It is shown experimentally that the diodes operating in microwave integrated circuits intensely emit light in the IR range with wavelengths from 890 to 910 nm. The obtained results indicate the necessity of taking into account the features of recombination processes in the GaAs-based microwave p-i-n diodes.     

Electrical Properties of <Emphasis Type="Italic">p</Emphasis>-NiO/<Emphasis Type="Italic">n</Emphasis>-Si Heterostructures Based on Nanostructured Silicon

Silicon nanowires are formed on n-Si substrates by chemical etching. p-NiO/n-Si heterostructures are fabricated by reactive magnetron sputtering. The energy diagram of anisotype p-NiO/n-Si heterostructures is constructed according to the Anderson model. The current–voltage and capacitance–voltage characteristics are measured and analyzed. The main current-transport mechanisms through the p-NiO/n-Si heterojunction under forward and reverse biases are established.     

<Emphasis Type="Italic">EIAS-CP:</Emphasis> new efficient identity-based authentication scheme with conditional privacy-preserving for VANETs

In VANETs, vehicles broadcast traffic-related messages periodically according to Dedicated Short Range Communication protocol. To ensure the reliability and integrity of messages, authentication schemes are involved in VANETs. As traffic-related messages are time-sensitive, they must be verified and processed timely, or it may cause inestimable harm to the traffic system. However, the OBUs and the RSUs are limited in computation ability and cannot afford vast messages’ verification. Recently, some identity-based authentication schemes using bilinear pairing have been proposed to improve the efficiency of message verification for VANETs. Nevertheless, the bilinear pairing is not suited for VANETs due to its complex operations. The design of an efficient and secure authentication scheme with low computation cost for VANETs still is a rewarding challenge. To settle this challenge, a new efficient identity-based authentication scheme is proposed in this paper. The proposed scheme ensures reliability and integrity of messages and provides conditional privacy-preserving. Compared with the most recent proposed authentication schemes for VANETs, the computation costs of the message signing and verification in the proposed scheme reduce by 88 and 93 % respectively, while security analysis demonstrates that our proposed scheme satisfies all security and privacy requirements for VANETs.     

A DLTS study of 4<Emphasis Type="Italic">H</Emphasis>-SiC-based <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> junctions fabricated by boron implantation

Deep-level transient spectroscopy (DLTS) has been used to study p-n junctions fabricated by implantation of boron into epitaxial 4H-SiC films with n-type conductivity and the donor concentration (8–9) × 10¹⁴ cm⁻³. A DLTS signal anomalous in sign is observed; this signal is related to recharging of deep compensating boron-involved centers in the n-type region near the metallurgical boundary of the p-n junction.     

Current flow mechanism in ohmic contact to <Emphasis Type="Italic">n</Emphasis>-4<Emphasis Type="Italic">H</Emphasis>-SiC

Current flow in an In-n-4H-SiC ohmic contact (n ≈ 3 × 10¹⁷ cm⁻³) has been studied by analyzing the temperature dependence of the per-unit-area contact resistance. It was found that the thermionic emission across an ∼0.1-eV barrier is the main current flow mechanism and the effective Richardson constant is ∼2 × 10⁻² A cm⁻² K⁻¹.     

Characterization of <Emphasis Type="Italic">n</Emphasis>-Type and <Emphasis Type="Italic">p</Emphasis>-Type Long-Wave InAs/InAsSb Superlattices

The influence of dopant concentration on both in-plane mobility and minority carrier lifetime in long-wave infrared InAs/InAsSb superlattices (SLs) was investigated. Unintentially doped (n-type) and various concentrations of Be-doped (p-type) SLs were characterized using variable-field Hall and photoconductive decay techniques. Minority carrier lifetimes in p-type InAs/InAsSb SLs are observed to decrease with increasing carrier concentration, with the longest lifetime at 77 K determined to be 437 ns, corresponding to a measured carrier concentration of p ₀ = 4.1 × 10¹⁵ cm^?3. Variable-field Hall technique enabled the extraction of in-plane hole, electron, and surface electron transport properties as a function of temperature. In-plane hole mobility is not observed to change with doping level and increases with reducing temperature, reaching a maximum at the lowest temperature measured of 30 K. An activation energy of the Be-dopant is determined to be 3.5 meV from Arrhenius analysis of hole concentration. Minority carrier electrons populations are suppressed at the highest Be-doping levels, but mobility and concentration values are resolved in lower-doped samples. An average surface electron conductivity of 3.54 × 10^?4 S at 30 K is determined from the analysis of p-type samples. Effects of passivation treatments on surface conductivity will be presented.     

Photoconductivity Amplification in a Type-II <Emphasis Type="Italic">n</Emphasis>-GaSb/InAs/<Emphasis Type="Italic">p</Emphasis>-GaSb Heterostructure with a Single QW

Significant photocurrent/photoconductivity amplification is observed at low reverse biases in a type-II n-GaSb/InAs/p-GaSb heterostructure with a single quantum well (QW), grown by metal-organic vapor phase epitaxy. A sharp increase in the photocurrent by more than two orders of magnitude occurs under exposure of the heterostructure to monochromatic light with a wavelength of 1.2–1.6 μm (at 77 K) and the application of a reverse bias in the range 5–200 mV. The optical gain depends on the applied voltage and increases to 2.5 × 10² at a reverse bias of 800 mV. Theoretical analysis demonstrated that the main role in the phenomenon is played by the screening of the external electric field by electrons accumulated in the deep InAs QW and by the mechanism of the tunneling transport of carriers with a small effective mass. It is shown that the effect under study is common to both isotype and anisotype type-II heterojunctions, including structures with QWs and superlattices.     

Electromagnetic Modeling of <Emphasis Type="Italic">n</Emphasis>-on-<Emphasis Type="Italic">p</Emphasis> HgCdTe Back-Illuminated Infrared Photodiode Response

The mercury cadmium telluride (MCT) photodiode is a well-known detector for infrared (IR) sensing. Its growth (mainly liquid phase epitaxy (LPE)) and photovoltaic technology (ion implantation planar technology for instance) for second-generation IR detectors (linear and 2D monospectral arrays) now appear to be mature, well mastered, and understood, and allow optimal detection in a wide range of spectral bands. However, the next generation of IR detectors is supposed to use more sophisticated structures and technologies (such as mesa technology for dual-band detection or advanced heterostructures for high-operating-temperature detectors). Such structures are usually grown by molecular beam epitaxy (MBE) and consist of a layered stack of different thicknesses, HgCdTe (MCT) compositions, and doping levels. Moreover, pitches accessible today with advanced hybridization techniques (20 μm or less) tend to approach the diffraction limit, especially for long-wave (LWIR) and very long-wave (VLWIR) devices. Hence, the physical understanding of these third-generation pixels from an electromagnetic (EM) point of view is not straightforward as it will have to take into account diffraction effects in the pixels. This paper will focus on EM simulation of advanced MCT detectors, using finite element modeling (FEM) to solve Maxwell’s equations in a two-dimensional (2D) configuration and calculate absorption in the pixel. The corresponding collected current is then estimated by introducing a simple diffusion modeled diode and is compared to spot-scan experiments and/or experimental spectral responses to validate the method.     

Study of the intermediate layer at the <Emphasis Type="Italic">n</Emphasis><Superscript>+</Superscript>-CdS/<Emphasis Type="Italic">p</Emphasis>-CdTe interface

The effect of production conditions and subsequent stimulation by ultrasonic irradiation on the formation of a solid solution at the n-CdS/p-CdTe interface in solar cells has been investigated. The phase composition of the solid-solution transient layer was investigated by a nondestructive photoelectric method (measurement of the spectral distribution of photosensitivity in the gate and photodiode modes). It is shown that the phase composition and thickness of the intermediate CdTe_1?x S _x layer depend strongly on the heterostructure formation conditions.