Dissociation energies of a C<Subscript>i</Subscript>C<Subscript>s</Subscript> complex and the <Emphasis Type="Italic">A</Emphasis> center in silicon

Reactions of annealing of A centers (VO) and complex centers consisting of interstitial carbon atoms and substitutional carbon atoms (C_iC_s) in n-Si irradiated with fast electrons or ⁶⁰Co gamma quanta were analyzed. The kinetics of isochronous annealing of the above centers was evaluated. By comparing the results of calculations with published experimental data, which were obtained by measuring the concentration of centers with the level E_c?0.17 eV in the course of isochronous heat treatment of irradiated n-Si, the dissociation energy E for the C_iC_s complex was estimated at 1.10±0.05 eV. The activation energy for annealing of this center was found to be equal to \(E_{aC_i C_s } \approx 2.0eV\). The dissociation energy for the A center was estimated at E_A=1.94 eV.     

Characterization of an <Emphasis Type="Italic">a</Emphasis>-Si:H/<Emphasis Type="Italic">c</Emphasis>-Si interface by admittance spectroscopy

The capabilities of admittance spectroscopy for the investigation of a-Si:H/c-Si heterojunctions are presented. The simulation and experimental results, which compare very well, show that the admittance technique is sensitive to the parameters of both the a-Si:H layer and the a-Si:H/c-Si interface quality. In particular, the curves showing capacitance versus temperature have two steps, accompanied by two bumps in the temperature dependence of the conductance. The first step, occurring in the low temperature range (100–200 K), is related to the transport and response of gap states in the a-Si:H layer. The second step, occurring at higher temperatures (>200 K), is caused by a carrier exchange with interface states and appears when the interface defect density exceeds 5 × 10¹² cm^?2. Then, the interface defects affect band bending, and, thus, the activation energy of de-trapping, which favors exchange with electrons from a-Si:H and holes from c-Si, respectively, for an increasing defect density.     

Structural and Electrical Properties of Ag/<Emphasis Type="Italic">n</Emphasis>-TiO<Subscript>2</Subscript>/<Emphasis Type="Italic">p</Emphasis>-Si/Al Heterostructure Fabricated by Pulsed Laser Deposition Technique

We have investigated the structural and electrical characteristics of the Ag/n-TiO₂/p-Si/Al heterostructure. Thin films of pure TiO₂ were deposited on p-type silicon (100) by optimized pulsed laser ablation with a KrF-excimer laser in an oxygen-controlled environment. X-ray diffraction analysis showed the formation of crystalline TiO₂ film having a tetragonal texture with a strong (210) plane as the preferred direction. High purity aluminium and silver metals were deposited to obtain ohmic contacts on p-Si and n-TiO₂, respectively. The current–voltage (I–V) characteristics of the fabricated heterostructure were studied by using thermionic emission diffusion mechanism over the temperature range of 80–300 K. Parameters such as barrier height and ideality factor were derived from the measured I–V data of the heterostructure. The detailed analysis of I–V measurements revealed good rectifying behavior in the inhomogeneous Ag/n-TiO₂/p-Si(100)/Al heterostructure. The variations of barrier height and ideality factor with temperature and the non-linearity of the activation energy plot confirmed that barrier heights at the interface follow Gaussian distributions. The value of Richardson’s constant was found to be 6.73 × 10⁵ Am^?2 K^?2, which is of the order of the theoretical value 3.2 × 10⁵ Am^?2 K^?2. The capacitance–voltage (C–V) measurements of the heterostructure were investigated as a function of temperature. The frequency dependence (Mott–Schottky plot) of the C–V characteristics was also studied. These measurements indicate the occurrence of a built-in barrier and impurity concentration in TiO₂ film. The optical studies were also performed using a UV–Vis spectrophotometer. The optical band gap energy of TiO₂ films was found to be 3.60 eV.     

Spectral photosensitivity of <Emphasis Type="Italic">a</Emphasis>-SiGe:H/<Emphasis Type="Italic">c</Emphasis>-Si heterostructures

Characteristics of a-SiGe:H/c-Si heterostructures produced by rapid plasma-chemical low-frequency (55 kHz) deposition are studied. High photosensitivity of a-SiGe:H films is established. The spectral position of the maximum of photosensitivity of a a-SiGe:H/c-Si heterostructure can be varied from 830 to 920 nm by increasing the content of germanium in an a-SiGe:H alloy and decreasing its band gap.     

Effects of Nb Content on the Ferroelectric and Dielectric Properties of Nb/Nd-Co-doped Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> Thin Films

Nd/Nb-co-substituted Bi_3.15Nd_0.85Ti_3?x Nb _x O₁₂ (BNTN _x , x = 0.01, 0.03, 0.05 and 0.07) thin films were grown on Pt/Ti/SiO₂/Si (100) substrates by chemical solution deposition. The effects of Nb content on the micro-structural, dielectric, ferroelectric, leakage current and capacitive properties of the BNTN _x thin films were investigated. A low-concentration substitution with Nb ions in BNTN _x can greatly enhance its remanent polarization (2P _r) and reduce the coercive field (2E _c) compared with those of Bi₄Ti₃O₁₂ (BIT) thin film. The highest 2P _r (71.4 μC/cm²) was observed in the BNTN_0.03 thin film when the 2E _c was 202 kV/cm. Leakage currents of all the films were on the order of 10^?6 to 10^?5 A/cm², and the BNTN_0.03 thin film has a minimum leakage current (2.1 × 10^?6 A/cm²) under the high electric field (267 kV/cm). Besides, the C–V curve of the BNTN_0.03 thin film is the most symmetrical, and the maximum tunability (21.0%) was also observed in this film. The BNTN_0.03 thin film shows the largest dielectric constant and the lowest dielectric loss and its maximum Curie temperature is 410 ± 5°C.     

Effect of the magnetic phase transition on the charge transport in layered semiconductor ferromagnets TlCrS<Subscript>2</Subscript> and TlCrSe<Subscript>2</Subscript>

TlCrS₂ and TlCrSe₂ crystals were synthesized by solid-state reaction. X-ray diffraction analysis showed that TlCrS₂ and TlCrSe₂ compounds crystallize in the hexagonal crystal system with lattice parameters a = 3.538 Å, c = 21.962 Å, c/a ≈ 6.207, z = 3; a = 3.6999 Å, c = 22.6901 Å, c/a ≈ 6.133, z = 3; and X-ray densities ρ _x = 6.705 and 6.209 g/cm³, respectively. Magnetic and electric studies in a temperature range of 77–400 K showed that TlCrS₂ and TlCrSe₂ are semiconductor ferromagnets. Rather large deviations of the experimental effective magnetic moment of TlCrS₂ (3.26 μ_B) and TlCrSe₂ (3.05 μ_B) from the theoretical one (3.85 μ_B) are attributed to two-dimensional magnetic ordering in the paramagnetic region of strongly layered ferromagnets TlCrS₂ and TlCrSe₂. The effect of the magnetic phase’s transition on the charge transport in TlCrS₂ and TlCrSe₂ is detected.     

Study of Deep Levels in a HIT Solar Cell

The results of studying a HIT (heterojunction with an intrinsic thin layer) Ag/ITO/a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(n⁺)/ITO/Ag solar cell by the capacitance–voltage characteristic and current deep-level relaxation transient spectroscopy methods are presented. The temperature dependence of the capacitance–voltage characteristics of the HIT structure and deep-energy-level parameters are studied. The results of comprehensive studies by the above methods are used to determine the features of the energy-band diagram of actual HIT structures.     

Special features of charge transport in PbGa<Subscript>2</Subscript>Se<Subscript>4</Subscript> crystals

The current-voltage (I-V) characteristics of PbGa₂Se₄ single crystals grown by the Bridgman-Stockbarger method with a resistivity of 10¹⁰–10¹² Ω cm were measured. The value of the majority carrier mobility μ=14 cm² V^?1 s^?1, calculated by the differential method of analysis of I-V characteristics, makes it possible to evaluate a number of parameters: the carrier concentration at the cathode (n_c0=2.48 cm^?3), the width of the contact barrier d_c=5.4×10^?8 cm, the cathode transparency D _c ^* =10^?5–10^?4 eV, and the quasi-Fermi level E_F=0.38 eV. It is found that a high electric field provides the charge transport through PbGa₂Se₄ crystals in accordance with the Pool-Frenkel effect. The value of the dielectric constant calculated from the Frenkel factor is found to be equal to 8.4.     

Microwave Dielectric Properties of BiCu<Subscript>2</Subscript>PO<Subscript>6</Subscript> Ceramics with Low Sintering Temperature

A BiCu₂PO₆ microwave dielectric ceramic was prepared using a solid-state reaction method. As the sintering temperature increased from 800°C to 880°C, the bulk density of BiCu₂PO₆ ceramic increased from 6.299 g/cm³ to 6.366 g/cm³; the optimal temperature was 860°C. The best microwave dielectric properties [permittivity (? _r ) = ～16, a quality factor (Q × f) = ～39,110 GHz and a temperature coefficient of resonant frequency (τ _f ) = ～?59 ppm/°C] were obtained in the ceramic sintered at 860°C for 2 h. Then, TiO₂ with a positive τ _f (～+400 ppm/°C) was added to compensate the τ _f value. The composite material was found to have a near-zero τ _f (+2.7 ppm/°C) and desirable microwave properties (? _r  = 19.9, Q × f = 24,885 GHz) when synthesized at a sintering temperature of 880°C. This system could potentially be used for low-temperature co-fired ceramics technology applications.     

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.     

Optical storage on the basis of an <Emphasis Type="Italic">n</Emphasis>-InSb-SiO<Subscript>2</Subscript>-<Emphasis Type="Italic">p</Emphasis>-Si heterostructure

The presence of potential barriers and deep traps in n-InSb/SiO₂/p-Si heterostructures makes it possible to realize the optical memory function on the basis of this structure. The maximal memory coefficient measured on the forward current voltage characteristic is as large as ～10⁴. This heterostructure can be used as an optoelectronic memory cell, which provides a means not only for the storage of signals but also for their summation.     

Electronic Processes in CdIn<Subscript>2</Subscript>Te<Subscript>4</Subscript> Crystals

The results of investigations of electrical, optical, and photoelectric properties of CdIn₂Te⁴ crystals, which were grown by the Bridgman method are presented. It is shown that electrical conductivity is determined mainly by electrons with the effective mass m_n = 0.44m₀ and the mobility 120–140 cm²/(V s), which weakly depends on temperature. CdIn₂Te₄ behaves as a partially compensated semiconductor with the donor-center ionization energy E_d = 0.38 eV and the compensation level K = N_a/N_d = 0.36. The absorption-coefficient spectra at the energy hν < E_g = 1.27 eV are subject to the Urbach rule with a typical energy of 18–25 meV. The photoconductivity depends on the sample thickness. The diffusion length, the charge-carrier lifetime, and the surface-recombination rate are determined from the photoconductivity spectra.     

Effect of copper doping on kinetic phenomena in <Emphasis Type="Italic">n</Emphasis>-Bi<Subscript>2</Subscript>Te<Subscript>2.85</Subscript>Se<Subscript>0.15</Subscript>

In single crystals of copper-doped and undoped Bi₂Te_2.85Se_0.15 solid solutions with an electron concentration close to 1 × 10¹⁹ cm^?3, the temperature dependences are investigated for the Hall (R ₁₂₃, R ₃₂₁) and Seebeck (S ₁₁) kinetic coefficients, the electrical-conductivity (σ ₁₁), Nernst-Ettingshausen (Q ₁₂₃), and thermalconductivity (k ₁₁) coefficients in the temperature range of 77–400 K. The absence of noticeable anomalies in the temperature dependences of the kinetic coefficients makes it possible to use the one-band model when analyzing the experimental results. Within the framework of the one-band model, the effective mass of density of states (m _d ≈ 0.8m ₀), the energy gap (ε_g ≈ 0.2 eV), and the effective scattering parameter (r _eff ≈ 0.2) are estimated. The obtained value of the parameter r _eff is indicative of the mixed electron-scattering mechanism with the dominant scattering by acoustic phonons. Data on the thermal conductivity and the lattice resistivity obtained by subtracting the electron contribution according to the Wiedemann-Franz law are presented.     

<Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript>-Si-<Emphasis Type="Italic">n</Emphasis>-CdF<Subscript>2</Subscript> heterojunctions

Boron diffusion and the vapor-phase deposition of silicon layers are used to prepare ultrashallow p⁺-n junctions and p⁺-Si-n-CdF₂ heterostructures on an n-CdF₂ crystal surface. Forward portions of the I–V characteristics of the p⁺-n junctions and p⁺-Si-n-CdF₂ heterojunctions reveal the CdF₂ band gap (7.8 eV), as well as allow the identification of the valence-band structure of cadmium fluoride crystals. Under conditions in which forward bias is applied to the p⁺-Si-n-CdF₂ heterojunctions, electroluminescence spectra are measured for the first time in the visible spectral region.     

Electrical properties of Si:H/<Emphasis Type="Italic">p</Emphasis>-Si structures fabricated by hydrogen implantation

Hydrogenated silicon (Si:H) layers and Si:H/p-Si heterostructures were produced by multiple-energy (3–24 keV) high-dose (5×10¹⁶–3×10¹⁷ cm^?2) hydrogen implantation into p-Si wafers. After implantation, current transport across the structures is controlled by the Poole-Frenkel mechanism, with the energy of the dominating emission center equal to E _c ?0.89 eV. The maximum photosensitivity is observed for structures implanted with 3.2×10¹⁷ cm^?2 of hydrogen and annealed in the temperature range of 250–300°C. The band gap of the Si:H layer E _g ≈2.4 eV, and the dielectric constant ?≈3.2. The density of states near the Fermi level is (1–2)×10¹⁷ cm^?3 eV^?1.     

Electrical and photoelectric properties of <Emphasis Type="Italic">n</Emphasis>-TiN/<Emphasis Type="Italic">p</Emphasis>-Hg<Subscript>3</Subscript>In<Subscript>2</Subscript>Te<Subscript>6</Subscript> heterostructures

n-TiN/p-Hg₃In₂Te₆ heterostructures are fabricated by depositing a thin n-type titanium nitride (TiN) film onto prepared p-type Hg₃In₂Te₆ plates using reactive magnetron sputtering. Their electrical and photoelectric properties are studied. Dominant charge-transport mechanisms under forward bias are analyzed within tunneling-recombination and tunneling models. The fabricated n-TiN/p-Hg₃In₂Te₆ structures have the following photoelectric parameters at an illumination intensity of 80 mW/cm²: the open-circuit voltage is V_OC = 0.52 V, the short-circuit current is I_SC = 0.265 mA/cm², and the fill factor is FF = 0.39.     

Study of Current Flow Mechanisms in a CdS/<Emphasis Type="Italic">por</Emphasis>-Si/<Emphasis Type="Italic">p</Emphasis>-Si Heterostructure

The temperature dependence of the forward and reverse portions of the current–voltage characteristic and the photovoltage spectrum of a CdS/por-Si/p-Si semiconductor heterostructure are studied. It is found that the current-flow mechanisms are controlled by generation–recombination processes in the spacecharge region of the por-Si/p-Si heterojunction, carrier tunneling in the por-Si film, and the model of space-charge-limited currents. A simplified version of the energy-band diagram of the heterostructure under study is proposed.     

A new type of high-efficiency bifacial silicon solar cell with external busbars and a current-collecting wire grid

Results regarding bifacial silicon solar cells with external busbars are presented. The cells consist of [n⁺p(n)p⁺] Cz-Si structures with a current-collecting system of new design: a laminated grid of wire external busbars (LGWEB). A LGWEB consists of a transparent conducting oxide film deposited onto a Si structure, busbars adjacent to the Si structure, and a contact wire grid attached simultaneously to the oxide and busbars using the low-temperature lamination method. Bifacial LGWEB solar cells demonstrate record high efficiency for similar devices: 17.7%(n-Si)/17.3%(p-Si) with 74–82% bifaciality for the smooth back surface and 16.3%(n-Si)/16.4%(p-Si) with 89% bifaciality for the textured back surface. It is shown that the LGWEB technology can provide an efficiency exceeding 21%.     

Dielectric Properties of (Bi<Subscript>0.5</Subscript>K<Subscript>0.5</Subscript>)ZrO<Subscript>3</Subscript> Modified (K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)NbO<Subscript>3</Subscript> Ceramics as High-Temperature Ceramic Capacitors

(1???x)K_0.5Na_0.5NbO₃-x(Bi_0.5K_0.5)ZrO₃ [abbreviated as (1???x)KNN-xBKZ, 0?≤?x?≤?0.08] lead-free ceramics have been fabricated by a solid-state processing route. Based on the x-ray diffraction data and temperature-dependent dielectric characteristics, an orthorhombic phase for x?≤?0.03 and single rhombohedral one for x?≥?0.05 at room temperature were determined. The cell volume firstly increases, then decreases and finally increases with increasing BKZ, depending on ionic size and crystallographic structure. For the sample of x?=?0.05, a temperature-stable high permittivity (~?1736?±?15%) along with low dielectric loss tangent (≤?5%) is recorded from 158°C to 407°C. In addition, the activation energies of dielectric relaxation and dc conductivity at high temperatures were characterized by impedance spectroscopy. A combined effect of lattice distortion and oxygen vacancies on the magnitude of activation energies was discussed.     

Study of the correlation properties of the surface structure of <Emphasis Type="Italic">nc</Emphasis>-Si/<Emphasis Type="Italic">a</Emphasis>-Si:H films with different fractions of the crystalline phase

The correlation properties of the structure of nc-Si/a-Si:H films with different volume fractions of the crystalline phase are studied using 2D detrended fluctuation analysis. Study of the surface relief of experimental samples showed that with increasing in volume fraction of the crystalline phase in the nc-Si/a-Si:H films, the size and number of nanoclusters on their surface grow. The size of Si nanocrystals in the a-Si:H matrix (6–8 nm) indicates the formation of coarse nanoclusters due to the self-organization of Si nanocrystals in groups under laser radiation. According to 2D detrended fluctuation analysis data, the number of correlation vectors (harmonic components) in the nc-Si/a-Si:H film structure increased with an increase in the nanocrystal fraction in the films.