High-voltage (900 V) 4 <Emphasis Type="Italic">H</Emphasis>-SiC Schottky diodes with a boron-implanted guard <Emphasis Type="Italic">p-n</Emphasis> junction

High-voltage (900 V) 4H-SiC Schottky diodes terminated with a guard p-n junction were fabricated and studied. The guard p-n junction was formed by room-temperature boron implantation with subsequent high-temperature annealing. Due to transient enhanced boron diffusion during annealing, the depth of the guard p-n junction was equal to about 1.7 μm, which is larger by approximately 1 μm than the projected range of 11 B ions in 4H-SiC. The maximum reverse voltage of fabricated 4H-SiC Schottky diodes is found to be limited by avalanche breakdown of the planar p-n junction; the value of the breakdown voltage (910 V) is close to theoretical estimate in the case of the impurity concentration N = 2.5 × 10¹⁵ cm^?3 in the n-type layer, thickness of the n-type layer d = 12.5 μm, and depth of the p-n junction r _j = 1.7 μm. The on-state diode resistance (3.7 mΩ cm²) is controlled by the resistance of the epitaxial n-type layer. The recovery charge of about 1.3 nC is equal to the charge of majority charge carriers that are swept out of an epitaxial n-type layer under the effect of a reverse voltage.     

Structurally complex two-hole and two-electron slow traps with bikinetic properties in <Emphasis Type="Italic">p</Emphasis>-ZnTe and <Emphasis Type="Italic">n</Emphasis>-ZnS crystals

Thermal-activation and photoactivation methods were used to ascertain the existence of two-hole traps in p-ZnTe crystals and two-electron traps in n-ZnS. It was found that these traps have a large number of energy states that are grouped in two series of levels: E_V+(0.46–0.66) eV and E_V+(0.06–0.26) eV in p-ZnTe and E_C?(0.6–0.65) eV and E_C?(0.14–0.18) eV in n-ZnS. Both the hole and the electron traps belong to the class of slow traps with bikinetic properties. These traps feature normal kinetic properties in the state with a single trapped charge carrier and feature anomalous kinetic properties in the state with two charge carriers. Multiple-parameter models allowing for a relation of traps in p-ZnTe and n-ZnS to the vacancy-impurity pairs distributed according to their interatomic distances and localized in the region of microinhomogeneities with collective electric fields that repel the majority charge carriers are suggested. The main special features of behavior of electron and hole traps are explained consistently using the above models.     

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.     

Self-Action of Intense Millimeter Waves in Waveguides with Integrated P-I-N Structures

The nonlinear interaction of high power millimeter (mm) electromagnetic waves with silicon integral p-i-n structures placed in a metal waveguide is theoretically investigated. The level of double injection of charge carriers due to detection of high intensity millimeter wave electric field in p-i-n structures is estimated. A mathematical model of the mutual influence of electromagnetic waves and injected charge carriers in the active region of p-i-n structures is formulated. A numerical solution of the nonlinear Helmholtz equation supplemented by proper boundary conditions on the active region boundary is obtained. The effect of high-power electromagnetic waves leads to an excessive injection of carriers into the active region of the semiconductor between p⁺-i, n⁺-i injection junctions and redistribution of the electric field in the structure. The reflection and transmission coefficients vary rapidly with the change in the input amplitude of the electromagnetic wave. This leads to bistability of these coefficients. The bistability is more pronounced in the low-frequency part of the mm range.     

The effect of the charge state of nonequilibrium vacancies on the nature of radiation defects in <Emphasis Type="Italic">n</Emphasis>-Si crystals

The aim of this study is to gain insight into the effect of the charge state of nonequilibrium vacancies on the processes that occur during irradiation and annealing in silicon crystals. n-Si floating-zone crystals with an electron concentration of N = 6 × 10¹³ cm^?3 are irradiated with 25-MeV protons at 300 K. The irradiated crystals are then studied by the Hall method at temperatures ranging from 77 to 300 K. It is shown that the nature and energy spectrum of radiation defects in n-Si crystals are mainly controlled by the charge state of nonequilibrium vacancies.     

Properties of correlators of thermal and photoinduced stochastic fields of charge-carrier concentrations and currents in IR photodiodes

A comparative analysis of the correlators of steady-state thermal and photoinduced stochastic fields (SFs) of concentrations and currents of mobile charge carriers in IR photodiodes and homogeneous semiconductors is presented. It is demonstrated that the correlators of thermal and photoinduced SFs of concentrations of mobile charge carriers are determined using conceptually identical expressions for any structure of the p–n junction and arbitrary polarity of applied voltage whereas the correlators of the SFs of photoinduced and dark currents are determined using conceptually identical expressions only for the reverse-biased p–n junction with a relatively wide base.     

Specific features of the electrophysical parameters of NTD Si treated under different conditions of heat treatment

The effect of thermal annealing in the temperature range 800 ? T_ann ? 1200°C and of two cooling rates (v_cl = 1 and 15°C min^–1) upon a change in the concentration of charge carriers in the conduction band, their mobility, and tensoresistance in n-Si crystals doped by nuclear transmutation and doped with phosphorus impurity via the melt (during growth by the Czochralski method) was investigated. It is found that, after annealing of all of the crystals at T_ann = 1050–1100°C, the concentration of charge carriers is increased by a factor of 1.3–1.7 compared to the initial concentration (irrespective of the method of doping). The specific annealing-temperature-dependent effect of cooling with a rate of 15°C min^–1 on the properties of transmutation-doped n-Si:P crystals is detected.     

Changes in the conductivity of lead-selenide thin films after plasma etching

The conductivity of epitaxial n- and p-PbSe thin films after dry etching in radio-frequency highdensity low-pressure inductively coupled argon plasma at a bombarding-ion energy of 200 eV is studied. It is shown that the observed changes in the conductivity can be adequately interpreted in the context of the classical model of the generation of donor-type radiation defects and that the processes of post-irradiation vacuum annealing result in the removal of such defects. The mean free path of charge carriers in p-PbSe films is determined within the context of the Fuchs–Sondheimer theory. It is found that, at room temperature, this parameter is 16 and 32 nm for the specularity parameter 0 and 0.5, respectively.     

Effect of thermal annealing of radiation defects on the noise characteristics of silicon <Emphasis Type="Italic">p-n</Emphasis> structures with a thin multiplication region

Specific features of changes in the noise spectral density and the lifetime of minority charge carriers in Si p-n structures with a thin multiplication region under thermal annealing of radiation defects were studied. It is shown that the change in the frequency characteristics of noise in p-n structures is related to the recovery of surface states. A qualitative explanation of self-limitation of the avalanche process in p-n structures with a thin multiplication region is suggested.     

Electron mobility in the inversion layers of fully depleted SOI films

The dependences of the electron mobility μ_eff in the inversion layers of fully depleted double–gate silicon-on-insulator (SOI) metal–oxide–semiconductor (MOS) transistors on the density N _e of induced charge carriers and temperature T are investigated at different states of the SOI film (inversion–accumulation) from the side of one of the gates. It is shown that at a high density of induced charge carriers of N _e > 6 × 10¹² cm^–2 the μeff(T) dependences allow the components of mobility μ_eff that are related to scattering at surface phonons and from the film/insulator surface roughness to be distinguished. The μ_eff(N _e ) dependences can be approximated by the power functions μ_eff(N _e) ∝ N _e ^?n . The exponents n in the dependences and the dominant mechanisms of scattering of electrons induced near the interface between the SOI film and buried oxide are determined for different N _e ranges and film states from the surface side.     

Effect of electrostatic shielding on the photoelectric properties of heterostructures with deep QWs

The effect of the electrostatic potential induced by charge carriers of the same sign, localized in a deep quantum well, on the current–voltage characteristics of photodetector heterostructures is theoretically analyzed. It is shown for the example of a p–i–n structure with a single deep quantum well in the i-type region that the shielding of an external electric field makes the differential photoconductivity of the heterostructure higher than that in a p–i–n structure without an intermediate 2D layer.     

Radiation-produced defects in germanium: Experimental data and models of defects

The problem of radiation-produced defects in n-Ge before and after n → p conversion is discussed in the light of electrical data obtained by means of Hall effect measurements as well as Deep Level Transient Spectroscopy. The picture of the dominant radiation defects in irradiated n-Ge before n → p conversion appears to be complicated, since they turn out to be neutral in n-type material and unobserved in the electrical measurements. It is argued that radiation-produced acceptors at ≈E _C – 0.2 eV previously ascribed to vacancy-donor pairs (E-centers) play a minor role in the defect formation processes under irradiation. Acceptor defects at ≈E _V + 0.1 eV are absolutely dominating in irradiated n-Ge after n → p conversion. All the radiation defects under consideration were found to be dependent on the chemical group-V impurities. Together with this, they are concluded to be vacancy-related, as evidenced positron annihilation experiments. A detailed consideration of experimental data on irradiated n-Ge shows that the present model of radiation-produced defects adopted in literature should be reconsidered.     

Modification of the properties of porous silicon on adsorption of iodine molecules

Infrared spectroscopy and electron spin resonance measurements are used to study the properties of porous silicon layers on adsorption of the I₂ iodine molecules. The layers are formed on the p-an n-Si single-crystal wafers. It is established that, in the atmosphere of I₂ molecules, the charge-carrier concentration in the layers produced on the p-type wafers can be noticeably increased: the concentration of holes can attain values on the order of ～10¹⁸?10¹⁹ cm^?3. In porous silicon layers formed on the n-type wafers, the adsorption-induced inversion of the type of charge carriers and the partial substitution of silicon-hydrogen bonds by silicon-iodine bonds are observed. A decrease in the concentration of surface paramagnetic defects, P _b centers, is observed in the samples with adsorbed iodine. The experimental data are interpreted in the context of the model in which it is assumed that both deep and shallow acceptor states are formed at the surface of silicon nanocrystals upon the adsorption of I₂ molecules.     

The influence of the energy of photoexcitation in the course of electron irradiation on defect formation in <Emphasis Type="Italic">n</Emphasis>-Si crystals

Effect of illumination of n-Si crystals in the course of irradiation with electrons on the nature of radiation defects is studied. The samples irradiated with 2-MeV electrons were subjected to isochronous annealing in the temperature range from 200 to 600°C. After each 20-min cycle of annealing, the electron concentration was measured by the Hall method in the temperature range 77–300 K. It is shown that, if the E centers are excited during irradiation with photons with the energy hν = 0.44 eV (the wavelength λ = 2.8 μm), divacancy phosphorus-containing defects of the PV ₂ type are formed in the n-Si crystals, which leads to an increase in the radiation resistance of the crystals under study. If negative vacancies V ^? are excited with photons with the energy hν = 0.28 eV (λ = 4.4 μm), the total number of radiation defects increases by a factor of 1.2.     

Field effect and capacitance of silicon crystals with hopping conductivity over point radiation defects pinning the Fermi level

The static field effect and capacitance of Si crystals with hopping conductivity over defects in the charge states (+1), (0), and (?1), which pin the Fermi level, are calculated. In the Si band gap, the defects in the (0) and (+1) charge states form a v′ band, and in the charge states (?1) and (0), they form a c′ band. The width of the c′ and v′ energy bands is calculated under the assumption of Coulomb interaction of each charged defect with only the nearest ion. The energy gap between the c′ and v′ bands is assumed to be constant. Nonmonotonicity of the dependence of capacitance and surface hopping conductivity on the electric potential on the surface of the highly damaged Si crystals is predicted.     

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.     

Effect of irradiation with fast neutrons on electrical characteristics of devices based on CVD 4<Emphasis Type="Italic">H</Emphasis>-SiC epitaxial layers

The effect of irradiation with 1-MeV neutrons on electrical properties of Al-based Schottky barriers and p⁺-n-n⁺ diodes doped by ion-implantation with Al was studied; the devices were formed on the basis of high-resistivity, pure 4H-SiC epitaxial layers possessing n-type conductivity and grown by vapor-transport epitaxy. The use of such structures made it possible to study the radiation defects in the epitaxial layer at temperatures as high as 700 K. Rectifying properties of the diode structures were no longer observed after irradiation of the samples with neutrons with a dose of 6×10¹⁴ cm^?2; this effect is caused by high (up to 50 GΩ) resistance of the layer damaged by neutron radiation. However, the diode characteristics of irradiated p⁺-n-n⁺ structures were partially recovered after an annealing at 650 K.     

Direct exchange between silicon nanocrystals and tunnel oxide traps under illumination on single electron photodetector

In this paper we present the trapping of photogenerated charge carriers for 300 s resulted by their direct exchange under illumination between a few silicon nanocrystals (ncs-Si) embedded in an oxide tunnel layer (SiO_x = 1.5) and the tunnel oxide traps levels for a single electron photodetector (photo-SET or nanopixel). At first place, the presence of a photocurrent limited in the inversion zone under illumination in the I–V curves confirms the creation of a pair electron/hole (e–h) at high energy. This photogenerated charge carriers can be trapped in the oxide. Using the capacitance-voltage under illumination (the photo-CV measurements) we show a hysteresis chargement limited in the inversion area, indicating that the photo-generated charge carriers are stored at traps levels at the interface and within ncs-Si. The direct exchange of the photogenerated charge carriers between the interface traps levels and the ncs-Si contributed on the photomemory effect for 300 s for our nanopixel at room temperature.     

X-ray conductivity of ZnSe single crystals

The experimental I–V and current–illuminance characteristics of the X-ray conductivity and X-ray luminescence of zinc-selenide single crystals feature a nonlinear shape. The performed theoretical analysis of the kinetics of the X-ray conductivity shows that even with the presence of shallow and deep traps for free charge carriers in a semiconductor sample, the integral characteristics of the X-ray conductivity (the current–illuminance and I–V dependences) should be linear. It is possible to assume that the nonlinearity experimentally obtained in the I–V and current–illuminance characteristics can be caused by features of the generation of free charge carriers upon X-ray irradiation, i.e., the generation of hundreds of thousands of free charge carriers of opposite sign in a local region with a diameter of <1 μm and Coulomb interaction between the free charge carriers of opposite signs.     

Electrical and thermoelectric properties of <Emphasis Type="Italic">p</Emphasis>-Ag<Subscript>2</Subscript>Te

Temperature dependences of the Hall coefficient R, electrical conductivity σ, and thermopower α₀ are investigated in the range of 4–300 K. The specific features observed in temperature dependences R(T), σ(T), and α₀(T) are interpreted in the context of a model with two types of charge carriers.