Single-crystalline GaAs, AlGaAs, and InGaAs layers grown by metalorganic VPE on porous GaAs substrates

Conditions for the growth of single-crystalline GaAs, AlGaAs, and InGaAs layers by metalorganic VPE were established and the corresponding semiconductor films were obtained on porous GaAs substrates. Comparative data on the morphology, structure, and electrical homogeneity of the epitaxial layers grown on the porous and monolithic substrates are presented. It was found that passage to the porous substrates leads to changes in the film growth rate and morphology, the concentration of electrically active defects, and their distribution in depth of the epitaxial structures.     

Effect of the parameters of sapphire substrates on the crystalline quality of GaN layers

The effect of certain types of sapphire substrate treatment on the properties of gallium nitride layers grown by metal-organic vapor-phase epitaxy is investigated.     

Martensitic transformation in an iron-nickel melt-quenched alloy

Metallography and X-ray diffraction analysis were used to study regularities of martensitic transformation in an N31 iron-nickel melt-quenched alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin ribbons of the alloy are related to the size effect of the transformation and structural nonuniformity of the ribbons.     

Control over carrier lifetime in high-voltage <Emphasis Type="Italic">p-i-n</Emphasis> diodes based on In<Subscript>x</Subscript>Ga<Subscript>1-<Emphasis Type="Italic">x</Emphasis></Subscript>As/GaAs heterostructures

The possibility of controlling the effective lifetime of nonequilibrium carriers by varying the lattice mismatch between the interfaced materials of a heterostructure has been studied on the example of InGaAs/GaAs heterostructures. It was found that, at a given composition (thickness) of a lightly doped layer of the InGaAs alloy, the nonequilibrium carrier lifetime depends on its thickness (composition), which enables variation of the nonequilibrium carrier lifetime from several nanoseconds to a microsecond without any significant change in the concentration of mobile carriers. The results obtained were used to fabricate pulse p ⁺-p ⁰-π-n ⁰-n ⁺ diodes with blocking voltages of up to 500 V, which can switch currents of ≥10 A and have recovery times no longer than 10 ns.     

New approach to the analysis of negative magnetostriction in two-dimensional structures

It is shown that the Fourier transform of the negative magnetoresistance associated with the interference correction to the conductivity contains information about the distribution function of the closed trajectories with respect to their areas and about the dependence of the length of the closed trajectories on their area . On the basis of this result a method is proposed for analyzing the negative magnetoresistance. It is used to process experimental results in a twodimensional structure with a doped barrier. It is shown that the function in the investigated structure is largely determined by the scattering anisotropy. Fiz. Tekh. Poluprovodn. 33, 986–989 (August 1999)     

Deep states in silicon δ-doped GaAs

The density and electron trapping cross section of deep states in silicon δ-doped GaAs were investigated by means of measurements of the voltage and temperature dependences of the impedance of a Schottky contact to the structure. It was observed that density-of-states tails appear in the band gap when the silicon density in the d-layer exceeds 6×10¹² cm⁻². In our structures the energy characterizing the penetration depth of a tail was in the range 20–100 meV. The characteristic electron trapping cross section of deep states in δ-layers was of the order of 10⁻¹⁷ cm². It was shown that saturation of the electron density in the δ-layer with increasing Si density is due to self-compensation of Si. Fiz. Tekh. Poluprovodn. 32, 733–738 (June 1998)     

Surface Instability and Chemical Reactivity of ZrSiS and ZrSiSe Nodal‐Line Semimetals

Materials exhibiting nodal‐line fermions promise superb impact on technology for the prospect of dissipationless spintronic devices. Among nodal‐line semimetals, the ZrSiX (X = S, Se, Te) class is the most suitable candidate for such applications. However, the surface chemical reactivity of ZrSiS and ZrSiSe has not been explored yet. Here, by combining different surface‐science tools and density functional theory, it is demonstrated that the formation of ZrSiS and ZrSiSe surfaces by cleavage is accompanied by the washing up of the exotic topological bands, giving rise to the nodal line. Moreover, while the ZrSiS has a termination layer with both Zr and S atoms, in the ZrSiSe surface, reconstruction occurs with the appearance of Si surface atoms, which is particularly prone to oxidation. It is demonstrated that the chemical activity of ZrSiX compounds is mostly determined by the interaction of the Si layer with the ZrX sublayer. A suitable encapsulation for ZrSiX should not only preserve their surfaces from interaction with oxidative species, but also provide a saturation of dangling bonds with minimal distortion of the surface.     

Electron transport effects in the IR photoconductivity of InGaAs/GaAs structures with quantum dots

We have studied the temperature dependence of the Hall effects in multilayer selectively doped InGaAs/GaAs heterostructures with quantum dots (QDs). It was found that structures possessing photoconductivity in the IR range exhibit a sharp (nearly exponential) growth of the conductivity and Hall mobility in the temperature interval from 8 to 30 K at a virtually constant Hall coefficient and electron density. A new mechanism of the lateral photoconductivity in the structures with QDs is proposed which is related to the change in the electron mobility in the two-dimensional channel as a result of a decrease in the Coulomb scattering on charged QDs.     

The Valence Band Structure of the [Ni(Salen)] Complex: An Ultraviolet,Soft X-ray and Resonant Photoemission Spectroscopy Study

The valence band photoemission (VB PE) spectra of the [Ni(Salen)] molecular complex were measured by ultraviolet, soft X-ray and resonant photoemission (ResPE) using photons with energies ranging from 21.2 eV to 860 eV. It was found that the Ni 3d atomic orbitals’ (AOs) contributions are most significant for molecular orbitals (MOs), which are responsible for the low-energy PE band at a binding energy of 3.8 eV in the VB PE spectra. In turn, the PE bands in the binding energies range of 8–16 eV are due to the photoionization of the MOs of the [Ni(Salen)] complex with dominant contributions from C 2p AOs. A detailed consideration was made for the ResPE spectra obtained using photons with absorption resonance energies in the Ni 2p_3/2, N 1s, and O 1s Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectra. A strong increase in the intensity of the PE band ab was found when using photons with an energy 854.4 eV in the Ni 2p_3/2 NEXAFS spectrum. This finding is due to the high probability of the participator-Auger decay of the Ni 2p_3/2⁻¹3d⁹ excitation and confirms the relationship between the PE band ab with the Ni 3d-derived MOs.