Features of an intermetallic <Emphasis Type="Italic">n</Emphasis>-ZrNiSn semiconductor heavily doped with atoms of rare-earth metals

The crystal structure, density of electron states, electron transport, and magnetic characteristics of an intermetallic n-ZrNiSn semiconductor heavily doped with atoms of rare-earth metals (R) have been studied in the ranges of temperatures 1.5–400 K, concentrations of rare-earth metal 9.5 × 10¹⁹–9.5 × 10²¹ cm⁻³, and magnetic fields H ≤ 15 T. The regions of existence of Zr_{1 − x} R _x NiSn solid solutions are determined, criteria for solubility of atoms of rare-earth metals in ZrNiSn and for the insulator-metal transition are formulated, and the nature of “a priori doping” of ZrNiSn is determined as a result of redistribution of Zr and Ni atoms at the crystallographic sites of Zr. Correlation between the concentration of the R impurity, the amplitude of modulation of the bands of continuous energies, and the degree of occupation of potential wells of small-scale fluctuations with charge carriers is established. The results are discussed in the context of the Shklovskii-éfros model of a heavily doped and compensated semiconductor.     

Features of electrical conductivity in the <Emphasis Type="Italic">n</Emphasis>-ZrNiSn intermetallic semiconductor heavily doped with the In acceptor impurity

The temperature and concentration dependences of resistivity and thermopower in a heavily doped and highly compensated semiconductor alloy ZrNiSn_1?x In _x in the temperature range T = 80–380 K at x = 0.005–0.15 are studied. It is assumed that the ZrNiSn semiconductor doped heavily with the In acceptor impurity is an amorphous semiconductor. It is experimentally established that there is a proportionality between the parameters of fluctuations in the bands of continuous energies, depth of fluctuations, and the depth of the potential well for a small-scale fluctuation. The conclusion advanced by Shklovski? and Éfros in 1972 [10] is experimentally confirmed for the first time; this conclusion is concerned with the assertion that, in a highly doped and completely compensated semiconductor, the maximum amplitude of fluctuations in the bands of continuous energies is equal to the half width of the band gap of the semiconductor, while the Fermi level is located near the midgap.     

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).     

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.     

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.     

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.     

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.     

Specific features of radiation-stimulated breakdown of a nonuniformly doped <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> junction

A quasi-hydrodynamic model of the transport of charge carriers under the ionizing effect of quantum radiation with the allowance made for the dynamics of heating of the semiconductor crystal by the flowing current is developed. Simulation of thermal breakdown of a nonuniformly doped p-n junction caused by a single radiation pulse is investigated. The variation in the times of relaxation of energy and pulse of electrons and suppression of the mechanism of impact ionization under the dynamic increase in the temperature of the semiconductor crystal is taken into account. The adequacy of the results of calculations is proved by comparing them with experimental data.     

On the charge-transport mechanisms in Cr-<Emphasis Type="Italic">n</Emphasis>-InP and Mo-<Emphasis Type="Italic">n</Emphasis>-InP diode structures

Electrical characteristics of Cr-n-InP and Mo-n-InP diode structures were investigated, and the charge-transport mechanism was estimated. It was established that this is either a thermionic or generation-recombination current that dominates in the Cr-n-InP structures, depending on temperature. In Mo-n-InP structures, the double injection of charge carriers dominates in the drift transport.     

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.     

Depolarization in a metal-<Emphasis Type="Italic">p</Emphasis>-ferroelectric-<Emphasis Type="Italic">n</Emphasis>-semiconductor structure

The depolarization in a metal-p-ferroelectric-n-semiconductor structure is calculated based on an analysis of the experimental parameters of a ferroelectric hysteresis loop in a metal-ferroelectric-metal structure. For a semiconductor, the Poisson equation is solved using a standard method, while, for a ferroelectric, a numerical integration is applied. Two variants of semiconductor parameters are considered: (i) a thick n-type region (there is a region of electrical neutrality beyond a space-charge region), and (ii) a thin n-type region (an electric field penetrates all the way through this region). It is shown that depolarization significantly reduces ferroelectric polarization, and this reduction is stronger in the case of a semiconductor with lower doping. If the electric field penetrates all the way through the n-type region, depolarization decreases as the n-type region becomes thinner.     

Features of structural,electron-transport,and magnetic properties of heavily doped <Emphasis Type="Italic">n</Emphasis>-ZrNiSn semiconductor: Fe acceptor impurity

Structural, energy, electron-transport, and magnetic characteristics of the n-ZrNiSn intermetallic semiconductor heavily doped with Fe (the concentration N _Fe ≈ 9.7 × 10¹⁹?3.8 × 10²¹ cm^?3) in the temperature range T = 80–380 K are investigated. It is shown that the Fe atoms simultaneously occupy crystallographic sites of Zr and Ni atoms in different relations being the defects of the donor and acceptor nature, respectively. The relation between the impurity concentration, the amplitude of large-scale fluctuation, and the degree of filling of the potential well of the small-scale fluctuation (fine structure) by charge carriers is established. The results are discussed within the context of the Shklovskii-Efros model of a heavily doped and compensated semiconductor.     

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.     

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.     

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.     

Practical Surface Treatments and Surface Chemistry of <Emphasis Type="Italic">n</Emphasis>-Type and <Emphasis Type="Italic">p</Emphasis>-Type GaN

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to study the electronic structure of n-GaN and p-GaN(0001) surfaces after three ex situ surface treatments: aq-HCl, annealing in NH₃, and annealing in HCl vapor. The combination of in situ vacuum annealing and re-exposure of samples to air revealed that the adsorption of ambient contaminants can reduce the surface state density and subsequent band bending on both n-GaN and p-GaN surfaces. Insights derived from first-principles calculations of the adsorption of relevant species on the Ga-terminated GaN(0001) surface are used to explain these experimental observations qualitatively.     

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.     

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.