Том 53, № 3 (2019)

This overview is devoted to the discovery, development of the technology, and investigation of III–V semiconductors performed at the Ioffe Institute, where the first steps in fabricating III–V semiconductors were taken in 1950 and investigations into their fundamental properties were begun under the leadership of two outstanding scientists—Nina Aleksandrovna Goryunova and Dmitry Nikolayevich Nasledov. Further development of these investigations is reflected in the works of followers and pupils of D.N. Nasledov, who have worked and continue to work at subsidiaries of the Ioffe Institute. The contribution of these investigations to studying heterostructures based on III–V compounds as well as to the development of semiconductor devices for electronics, optoelectronics, and photonics is considered.

The temperature dependences of the Raman-active frequencies \(E_{g}^{2}\), \(A_{{1g}}^{2}\) in layered Bi₂Se₃ single crystals are studied. The contribution of the thermal expansion to a temperature variation in the frequencies is determined. The decay of the anisotropy of the elastic properties in layered Bi₂Se₃ single crystals due to strong spin–orbit coupling is shown. The Gruneisen-mode parameters for phonons \(E_{g}^{2}\) and \(A_{{1g}}^{2}\) are calculated. Systematic features in the dependences of vibrational frequencies on the atomic masses in layered Bi₂Te₃, Bi₂Se₃, and Sb₂Te₃ single crystals are determined.

The electron-spin-resonance spectra of transition metal ions Fe in the HgSe matrix are analyzed. The spectra have an appearance typical of the Fe³⁺ ion, i.e., they consist of five fine-structure lines with a splitting that corresponds to a weak crystal field. The spectra are observed at temperatures of up to 50 K. The spectral lines are deformed and have a Dyson shape. An analysis of the temperature dependences of the line amplitudes shows that a transition from paramagnetic ordering to ferromagnetic ordering occurs with decreasing temperature, with the Curie temperature T ≈ 7 K.

It is established that the doping of ZnSe:Al crystals with ytterbium from the vapor phase brings about the appearance of two new bands in the low-temperature luminescence spectra. Emission in the energy range 1.15–1.35 eV is defined by transitions in Yb³⁺ ions, and the edge band is defined by the LO-phonon-assisted transitions of free electrons to acceptor levels of uncontrollable Li impurities.

Single-crystal n-Si(100) wafers are implanted with ⁶⁴Zn⁺ ions with an energy of 50 keV and dose of 5 × 10¹⁶ cm^–2. Then the samples are irradiated with ¹³²Xe²⁶⁺ ions with an energy of 167 MeV in the range of fluences from 1 × 10¹² to 5 × 10¹⁴ cm^–2. The surface and cross section of the samples are visualized by scanning electron microscopy and transmission electron microscopy. The distribution of implanted Zn atoms is studied by time-of-flight secondary-ion mass spectrometry. After irradiation with Xe, surface pores and clusters consisting of a Zn–ZnO mixture are observed at the sample surface. In the amorphized subsurface Si layer, zinc and zinc-oxide phases are detected. After irradiation with Xe with a fluence of 5 × 10¹⁴ cm^–2, no zinc or zinc-oxide clusters are detected in the samples by the methods used in the study.

The properties of InGaAs/GaAs quantum dots (QDs) grown by MOS-hydride migration-stimulated epitaxy at a reduced pressure using submonolayer deposition are investigated. The wavelength of their photoluminescence at 300 K is in the range of 1.28–1.31 μm and can be controlled by varying the growth temperature and the number of QD-deposition cycles. The highest QD surface density is 3 × 10¹⁰ cm^–2. Structures with 1–3 QD layers and spacer layers 5–12 nm thick between them are grown. The spacer layers (as well as the cap layers) are selectively doped with carbon (acceptor). It is established that the QD photoluminescence is characterized by an enhanced degree of polarization in the direction orthogonal to the structure plane. This should favor their use for the excitation of surface plasmon–polaritons in Schottky light-emitting diodes.

Metamorphic high-electron-mobility transistor (HEMT) structures based on deep In_0.2Ga_0.8As/In_0.2Al_0.8As quantum wells (0.7 eV for Γ electrons) with different metamorphic buffer designs are implemented and investigated for the first time. The electronic properties of metamorphic and pseudomorphic HEMT structures with the same doping are compared. It is found that, over a temperature range of 4–300 K, both the electron mobility and concentration in the HEMT structure with a linear metamorphic buffer are higher than those in the pseudomorphic HEMT structure due to an increase in the depth of the quantum well. Low-temperature magnetotransport measurements demonstrate that the quantum momentum-relaxation time decreases considerably in metamorphic HEMT structures because of enhanced small-angle scattering resulting from structural defects and inhomogeneities, while the dominant scattering mechanism in structures of both types is still due to remote ionized impurities.

The mechanism of the vapor–solid–solid growth of Au-catalyzed GaAs nanowires in the temperature range of 420–450°C is investigated. For the first time, the effect of elastic stresses caused by a difference in the atomic densities of the catalyst and nanowire material on the solid-phase nucleation rate is considered. By assuming that the growth of the GaAs nucleus at the catalyst–nanowire interface is limited  by the As-diffusion flux in the catalyst, it is shown that vapor–solid–solid growth can be implemented through the polycentric-nucleation mode in the temperature range under consideration. The intensity of the nucleation of coherent islands upon vapor–solid–solid growth is shown to be higher than the intensity of nucleation in the case of vapor–liquid–solid growth because a low interphase surface energy is implemented at coherent solid–solid conjugation. It is proved that the nucleation of Au-catalyzed GaAs nanowires by the vapor–solid–solid mechanism is possible only when GaAs-island growth proceeds due to As diffusion along the catalyst–nanowire interface.

The electrical properties of photodiodes based on silicon-on-sapphire structures are investigated theoretically and experimentally. It is shown that they are no worse than silicon diodes in terms of their basic parameters, while their radiation hardness is higher by an order of magnitude than that of similar diodes based on bulk silicon.

The simulations of recently discovered effect of subnanosecond avalanche switching of Si n⁺−n−n⁺-structures have been performed. The electric field in n⁺−n−n⁺-structure is shown to remain quasi-uniform along the current flow direction during the voltage rise stage and it reaches the effective threshold of impact ionization of ~200 kV/cm in the whole n-base. Comparing simulation results with experiments we argue that the field distribution is as well uniform in the transverse direction. Hense, the ultrafast avalanche transient develops quasi-uniformly in the whole n-base volume. The switching time is about ~150 ps. We compare numerical results obtained for various impact ionization models and estimate parameters of the initial voltage pulse that are required for ultrafast avalanche switching of n⁺−n−n⁺-structures.

The properties of gallium-oxide films produced by the radio-frequency magnetron-assisted sputtering of a β-Ga₂O₃ target with deposition onto sapphire substrates are studied. The as-deposited gallium-oxide films are polycrystalline and contain crystallites of the α and β phases. Exposure to oxygen plasma does not bring about the appearance of new crystallites but makes crystallites several times larger in average dimensions in the substrate plane. After annealing at 900°C, the crystallite size becomes twice as large as that in the unannealed film. The films not subjected to thermal annealing exhibit a high resistance at 20°C. In the range of 50–500°C, the conductivity of the samples (G) only slightly depends on temperature (T) and, as T is elevated further, exponentially increases with the activation energy 0.7–1.0 eV. After annealing of the films in argon at 900°C (30 min), the conductivity G starts to sharply increase at T ≈ 350°C. In the dependence of lnG on T  ^–1, a maximum in the range of 470–520°C and a portion of decreasing conductivity at higher temperatures are observed. The unusual temperature dependence of the conductivity after annealing is attributed to a change in the structure and phase composition of polycrystalline gallium-oxide films and, possibly, to some effects at the surface. The structures produced on insulating substrates are solar blind in the visible wavelength region and sensitive to radiation in the ultraviolet region (222 nm).

The processes of the crystallization of amorphous germanium films and multilayer germanium/silicon structures upon exposure to nanosecond (70 ns) ruby laser radiation (λ = 694 nm) are studied. The samples are grown on silicon and glassy substrates by plasma-enhanced chemical vapor deposition. Pulsed laser annealing of the samples is conducted in the range of pulse energy densities E_p from 0.07 to 0.8 J cm^–2. The structure of the films after annealing is determined by analyzing the scanning electron microscopy data and Raman spectra. It is established that, after annealing, the films are completely crystallized and, in this case, contain regions of coarse crystalline grains (>100 nm), whose fraction increases, as E_p is increased, and reaches 40% of the area. From analysis of the position of the Raman peaks, it is conceived that the crystalline grains, whose dimensions exceed 100 nm, either contain structural defects or stretching strains. The correlation length of optical vibrations is determined from the phonon confinement model and found to increase from 5 to 8 nm, as E_p is increased. Pulsed laser annealing of multilayer Ge(10 nm)/Si(5 nm) structures induces partial intermixing of the layers with the formation of Ge–Si alloys.