Effective electron mass in a Mn<Subscript>x</Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te system

The reflection spectra of n-Mn_xHg_1?xTe single crystals and epitaxial layers were measured at 300 K. The effective electron mass was determined for the samples with x=0.06–0.10 and an electron concentration N>6×10¹⁶ cm^?3. The calculated values of effective electron mass are close to experimental values.     

Thermoelectric figure of merit of Ag<Subscript>2</Subscript>Se with Ag and Se excess

In the temperature range of 100–300 K, the electric (σ) and thermoelectric (α₀) properties of Ag₂Se with an excess of Ag as high as ～0.1 at. % and Se as high as ～1.0 at. %, respectively, are investigated. From the data on σ, α₀, and χ_tot (thermal conductivities), the thermoelectric power α ₀ ² σ and the figure of merit Z are calculated. It is found that α ₀ ² σ and Z attain the peak values at room temperature and the electron concentration n ≈ 6.5 × 10¹⁸ cm^?3.     

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.     

Investigation of the ZnS-CdHgTe interface

The ZnS-Cd_xHg_1?xTe interface was investigated using the capacitance-voltage characteristics of MIS structures in experimental samples. During fabrication of the n⁺-p junctions based on p-Cd_xHg_1?xTe, the density of states within the range N _ss =(1–6)×10¹¹ cm^?2 eV^?1 at T=78 K was obtained. The experiments showed that the conditions in which n⁺-p junctions are fabricated only slightly affect the state of the ZnS-CdHgTe interface. The negative voltages of the at bands V _FB , even if immediately after deposition of the ZnS films V _FB >0, point to the enrichment of the ZnS-p-CdHgTe near-surface layer with majority carriers, specifically, holes. This led to a decrease in the leakage current over the surface. During long-term storage (as long as ～15 years) in air at room temperature, no degradation of differential resistance R _d , current sensitivity S _i , and detectivity D* of such n⁺-p junctions with a ZnS protection film was observed.     

Electrical properties and low-temperature photolumincesence of Si-doped CdTe crystals

The CdTe:Si single crystals with Si concentration in the range of C _Si ⁰ =2×10¹⁸–5×10¹⁹ cm^?3 are grown by the Bridgman-Stockbarger method. The samples were of the n-and p-type with electrical conductivity σ=2×10^?1–8×10^?9 Ω^?1 cm^?1. Being heated in the temperature range 300–440 K, the p-CdTe crystals were annealed, and their conductivity decreased. The shape of the low-temperature (5–20 K) photoluminescence spectra of the samples are indicative of their high structural quality. The specific feature of the emission of the CdTe:Si crystals is its decrease in the intensity of all lines induced by donors as the samples are cut progressively closer to the ingot top. The results obtained indicate that the Si impurity, in contrast with Ge, Sn, and Pb, does not exhibit the compensating and stabilizing effect in CdTe.     

Energy spectrum of charge carriers in TlIn<Subscript>1–<Emphasis Type="Italic">x</Emphasis> </Subscript>Yb<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>Te<Subscript>2</Subscript> solid solutions

The temperature dependences of the electrical conductivity σ(T), the Hall coefficient R(T), and the thermoelectric coefficient α(T) are investigated in TlIn_1–xYb_xTe₂ (0 < x < 0.10) solid solutions at 80–1000К. From the kinetic parameters, the effective masses of electrons and holes are determined. The obtained experimental data on σ(T) and α(T) are interpreted within the context of a model with one and two types of charge carriers. It is established that, since x = 0.05, the TlIn_1–xYb_xTe₂ solid solutions belong to the class of narrow-gap semiconductors that have high matrix elements of interaction.     

Interaction of charge carriers with the localized magnetic moments of manganese atoms in <Emphasis Type="Italic">p</Emphasis>-GaInAsSb/<Emphasis Type="Italic">p</Emphasis>-InAs:Mn heterostructures

Transport properties of p-Ga_1?xIn_xAs_ySb_1?y/p-InAs:Mn heterostructures with undoped layers of solid solutions similar in composition to GaSb (x?0.22) grown by liquid-phase epitaxy on substrates with a Mn concentration of (5–7)×10¹⁸ cm^?3 are studied. It is ascertained that there is an electron channel at the interface (from the InAs side). The anomalous Hall effect and negative magnetoresistance are observed at relatively high temperatures (77–200) K. These phenomena can be attributed to the s-d-exchange interaction between Mn ions of the substrate and s electrons of the two-dimensional channel. The effective magnetic moment of Mn ions was evaluated as μ=200µ_B at T=77 K.     

On the preparation and photoelectric properties of Tl1–x In1–x Sn x Se2 (x = 0.1–0.25) alloys

The technological conditions for growing single crystals of Tl_1–x In_1–x Sn _x Se₂ (x = 0.1–0.25) alloys are developed. The spectral distribution of the photoconductivity of the grown crystals at T = 300 K and thermally stimulated conductivity are studied. The effect of In³⁺cation substitution with Sn⁴⁺ in Tl_1–x In_1–x Sn _x Se₂ (x = 0.1–0.25) alloys on their photoelectric properties is shown.     

Specific thermoelectric properties of lightly doped Bi<Subscript>2</Subscript>(TeSe)<Subscript>3</Subscript> solid solutions

Electrical and thermoelectric properties of a lightly doped n-Bi₂Te_2.7Se_0.3 solid solution have been studied in the temperature range 77–300 K. The results are compared with data for the compound PbTe_0.9Se_0.1 with a similar magnitude of the Seebeck coefficient S at 84 K. Along with lower thermal conductivity, Bi₂Te_2.7Se_0.3 has a higher electrical conductivity σ and a much weaker temperature dependence. As a result, the power coefficient S ²σ in optimal samples begins to decrease only when the density of minority carriers becomes significant. In this case, |S| considerably exceeds the standard value of 200 μV/K. The reduction of the electron density reduces the thermoelectric figure of merit Z at its maximum and slightly lowers the temperature of the maximum; therefore, the expected effect on the average value of Z in the range 77–300 K is absent. Similar behavior is observed in Bi₂Te_2.88Se_0.12, although the effect is less pronounced. The experimental results are discussed taking into account possible changes in the dominant scattering mechanisms, carrier density, and electron energy spectrum. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 7, 2004, pp. 811–815. Original Russian Text Copyright ? 2004 by Konstantinov, Prokof’eva, Ravich, Fedorov, Kompaniets.     

Special features of annealing of radiation defects in irradiated <Emphasis Type="Italic">p</Emphasis>-Si crystals

p-Si single crystals grown by the Czochralski method were studied; the hole concentration in these crystals was p = 6 × 10¹³ cm^?3. The samples were irradiated with 8-MeV electrons at 300 K and were then annealed isochronously in the temperature range T _ann = 100–500°C. The studies were carried out using the Hall method in the temperature range of 77–300 K. It is shown that annealing of divacancies occurs via their transformation into the B _s V ₂ complexes. This complex introduces the energy level located at E _v + 0.22 eV into the band gap and is annealed out in the temperature range of 360–440°C. It is assumed that defects with the level E _v + 0.2 eV that anneal out in the temperature range T _ann = 340–450°C are multicomponent complexes and contain the atoms of the doping and background impurities.     

Specific features of conductivity of Cd<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>x</Subscript>Te and Cd<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript>x</Subscript>Te single crystals

The electrical characteristics of p-type Cd_1?xZn_xTe (x=0.05) and Cd_1?xMn_xTe (x=0.04) single crystals with a resistivity of 10³–10¹⁰ Ω cm at 300 K are studied. The conductivity and its variation with temperature are interpreted on the basis of statistics of electrons and holes in a semiconductor with deep acceptor impurities (defects), with regard to their compensation by donors. The depth of acceptor levels and the degree of their compensation are determined. The problems of attaining near intrinsic conductivity close to intrinsic are discussed.     

Low-temperature instabilities of the electrical properties of Cd<Subscript>0.96</Subscript>Zn<Subscript>0.04</Subscript>Te:Cl semi-insulating crystals

The electrical properties in the temperature range 295–430 K and low-temperature (4.2 K) photoluminescence of Cd_1?xZn_xTe:Cl semi-insulating crystals grown from melts with a variable impurity content (C _Cl ⁰ = 5 × 10¹⁷–1 × 10¹⁹ cm^?3) are investigated. Nonequilibrium processes leading to a decrease in carrier concentration are observed in all the samples at low temperatures (T = 330–385 K). These changes are reversible. The activation energy of these processes E _a is found to be 0.88 eV. As with semi-insulating CdTe:Cl, the observed phenomena can be explained by a change in the charge state of background copper atoms: Cu_Cd ? Cu_i. The introduction of Zn changes the ratio of the concentrations of shallow-level donors Cu_i and Cl_Te from their levels in the initial material.     

Dielectric waveguide for middle and far infrared radiation

The possibility of using the normal skin effect in dielectric waveguides for long-wavelength radiation is analyzed. A design of a waveguide integrated with a heterolaser is suggested, in which an undoped layer of GaAs is clad between heavily-doped n- and p-Al _x Ga_{1 ? x} As alloy layers, reflecting radiation because of the normal skin effect. It is shown that an efficient waveguide can be formed using n-Al _x Ga_{1 ? x} As layers with x < 0.45 and the electron concentration N > 5 × 10¹⁸ cm^?3 and p-Al _x Ga_{1 ? x} As layers of any composition with the hole concentration P ≥ 3 × 1019 cm^?3.     

Analysis of the magnetic properties of (La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>0.93</Subscript>MnO<Subscript>3</Subscript> manganites at high temperatures

For the first time, the Faraday method is used to measure the temperature dependence of paramagnetic susceptibility χ(T) of (La_{1 ? x} Sr _x )_0.93MnO₃ (x = 0.2, 0.25, or 0.3) manganites in the temperature interval 60–850°C. It is demonstrated that the dependences have two kinks and three linear sections. The kink of curve χ^?1(T) is related to polymorphic transformations (Q′ → Q* and Q* → R) that take place in the crystal lattices of the samples. The main magnetic characteristics of the samples are determined with the least-squares processing of curve χ^?1. Is is demonstrated that dependence χ^?1(T) obeys the Curie-Weiss law. The energy state of the magnetoactive manganese atom in the Q′-and Q*-phase samples is close to the energy state of a free Mn²⁺ ion. In the R phase, this state is close to the state of a free Mn³⁺ ion.     

Characterization of HgCdTe Films Grown on Large-Area CdZnTe Substrates by Molecular Beam Epitaxy

Recent advances in growth of Hg_1?x Cd _x Te films on large-area (7 cm × 7.5 cm) CdZnTe (CZT) substrates is presented. Growth of Hg_1?x Cd _x Te with good uniformity on large-area wafers is achieved using a Riber 412 molecular beam epitaxy (MBE) tool designed for growth of Hg_1?x Cd _x Te compounds. The reactor is equipped with conventional CdTe, Te, and Hg sources for achieving uniform exposure of the wafer during growth. The composition of the Hg_1?x Cd _x Te compound is controlled in situ by employing a closed-loop spectral ellipsometry technique to achieve a cutoff wavelength (λ _co) of 14 μm at 78 K. We present data on the thickness and composition uniformity of films grown for large-format focal-plane array applications. The composition and thickness nonuniformity are determined to be <1% over the area of a 7 cm × 7.5 cm wafer. The films are further characterized by Fourier-transform infrared spectroscopy, optical microscopy, and Hall measurements. Additionally, defect maps show the spatial distribution of defects generated during the epitaxial growth of the Hg_1?x Cd _x Te films. Microdefect densities are in the low 10³ cm^?2 range, and void defects are below 500 cm^?2. Dislocation densities less than 5 × 10⁵ cm^?2 are routinely achieved for Hg_1?x Cd _x Te films grown on CZT substrates. HgCdTe 4k × 4k focal-plane arrays with 15 μm pitch for astronomical wide-area infrared imagers have been produced using the recently developed MBE growth process at Teledyne Imaging Sensors.     

Special features of radiation-defect annealing in silicon <Emphasis Type="Italic">p-n</Emphasis> structures: The role of Fe impurity atoms

Deep-level transient spectroscopy is used to study the formation of complexes that consist of a radiation defect and a residual impurity atom in silicon. It is established that heat treatment of the diffused Si p⁺-n junctions irradiated with fast electrons lead to the activation of a residual Fe impurity and the formation of the FeVO (E_0.36 trap) and FeV₂ (H_0.18 trap) complexes. The formation of these traps is accompanied by the early (100–175°C) stage of annealing of the main vacancy-related radiation defects: the A centers (VO) and divacancies (V₂). The observed complexes are electrically active and introduce new electron (E_0.36: E _t ^e =E _c -0.365 eV, σ _n =6.8×10^?15 cm²) and hole (H_0.18: E _t ^h =E _v +0.184 eV, σ _p =3.0×10^?15 cm²) levels into the silicon band gap and have a high thermal stability. It is believed that the complex FeVO corresponds to the previously observed and unidentified defects that have an ionization energy of E _t ^e =E _c ?(0.34–0.37) eV and appear as a result of heat treatment of irradiated diffused Si p⁺-n junctions.     

MOCVD growth and Mg-doping of InAs layers

Epitaxial layers of Mg-doped InAs were grown by MOCVD, and electrical properties of these layers were studied. The doping with magnesium in the course of MOCVD growth allows one to obtain strongly compensated p-InAs with a high hole density (p≈2×10¹⁸ cm^?3) and a low carrier mobility (μ≈50 cm²/(V s)) at T=300 K. When the samples are lightly doped with Mg, neutral impurities are bound with Mg, and n-type InAs layers with a carrier mobility exceeding that in undoped samples are formed.     

Fine Structure of the long-wavelength edge of exciton-phonon absorption and hyperbolic excitons in silicon carbide of 6<Emphasis Type="Italic">H</Emphasis> polytype

The fine structure of the long-wavelength edge of the polarization spectra of exciton-phonon absorption in moderate-purity n-type 6H-SiC crystals with a concentration of uncompensated donors N_D?N_A=(1.7–2.0)×10¹⁶ cm^?3 at T=1.7 K was studied. The analysis of new special features found at the absorption edge and the reliable detection of the onset of exciton-phonon steps related to the emission of phonons from acoustical and optical branches allowed highly accurate determination of a number of important parameters such as the band gap, the exciton band gap, the exciton binding energy, and the energies of spin-orbit and crystal-field splitting of an exciton. For the first time, transitions with the emission of LA phonons to the 1S exciton state with an M₁-type dispersion law were detected in E ∥ Z(C) polarization (the electric-field vector is parallel to the optical axis of the crystal). This observation supports the previously predicted “two-well” structure of the conduction band minimum in 6H-SiC.     

Electrical properties of Zinc-Tin diarsenide (ZnSnAs<Subscript>2</Subscript>) irradiated with H<Superscript>+</Superscript> ions

The results of studying the electrical properties and isochronous annealing of p-ZnSnAs₂ irradiated with H⁺ ions (energy E = 5 MeV, dose D = 2 × 10¹⁶ cm^?2) are reported. The limiting electrical characteristics of irradiated material (the Hall coefficient R _H (D)_lim ≈ ?4 × 10³ cm³ C^?1, conductivity σ (D)_lim ≈ 2.9 × 10^?2 Ω^?1 cm^?1, and the Fermi level position F _lim ≈ 0.58 eV above the valence-band top at 300 K) are determined. The energy position of the “neutral” point for the ZnSnAs₂ compound is calculated.     

Features of the infrared reflection spectra of SmS semiconductor in the homogeneity range

Infrared reflection spectra in the range of 5200–380 cm^?1 were measured for polycrystalline samarium monosulfide samples in the semiconductor phase with compositions Sm_{1 + x} S lying within the homogeneity range (0 ≤ x ≤ 0.17) in the temperature range of 300–600 K. Five peaks with energies in the range of 1150–880 cm^?1, whose positions depend weakly on the composition and temperature. It was shown that the reflection peaks are associated with ⁷ F ₀–⁷ F ₂ transitions of 4f electrons of Sm²⁺ ions.