Search

An analysis of the I–V characteristics makes it possible to determine the mechanisms of conduction corresponding to different states of the flow channels upon resistive switching in porphyrazine films. A variation in the temperature, the structure of the dielectric matrix, and the type of majority charge carriers makes it possible to estimate the applicability of the model of conducting filaments for describing transport and determining the mechanisms of conduction for each state of the system.

The results of studies of the optical and transport properties of epitaxial Pb0.74Sn0.26Te(In) films with a differently treated surface are presented. A comparative analysis of the results makes it possible to establish that the characteristic features of the photoconductivity spectra are defined by processes in the bulk while the surface states have practically no effect on the spectra. At the same time, the photoresponse kinetics and the rate of relaxation processes are heavily dependent on the state of the surface. The characteristic relaxation times of nonequilibrium charge carriers (about several milliseconds) are such that it is possible to use the methods of standard Fourier-transform spectroscopy to characterize optical transitions in the bulk.

In this paper, we report on photoconductivity induced by high-power laser radiation with a frequency of 2 THz in Hg0.87Cd0.13Te-based epitaxial structures. Experimental results obtained for a set of the samples with variable geometric parameters allow us to determine the photoresponse features of both bulk and nonlocal contributions to the net response. We show that the persistent photoconductivity effect originates from the non-equilibrium processes related to the bulk carrier excitation.

The photoconductivity spectra of PbSnTe(In) epitaxial films are investigated by Fourier spectroscopy in the far infrared range at temperatures from 4.2 to 32.4 K. In addition to interband transitions, subgap features associated with the excitation of impurity-defect states are found in the spectra. The evolution of the spectra with temperature and additional illumination is traced.

The introduction of CsPbBr3 nanocrystals into a porous ZnO matrix leads to the appearance of a photoconductivity response in the visible spectral range. Measurement of the spectral dependences of the absorption, photoluminescence (PL), and photoconductivity showed that the shape and position of the PL peak are associated with defects in CsPbBr3. Analysis of the photoconductivity relaxation kinetics shows the possibility of accelerating the recombination of photoexcited charge carriers by more than an order of magnitude. The mechanisms responsible for this effect are discussed.

In this work, we conduct research of spectral and power characteristics of quantum cascade lasers (QCLs) based on a GaAs/Al0.15Ga0.85As active region emitting at 2.3 (A), 3.2 (B) and 4.1 (C) THz. The QCL devices had a double-metal Au waveguide and operated in pulsed mode with 1.5-9 μs pulses at 20 Hz repetition rate. Using the integral output power curves measured with different pulse durations, we consider the potential mechanisms of QCL temperature degradation using Arrhenius plots. Moreover, we present the spectra of the lasers measured at fixed operating points for devices A, C and with current scanning for device B in a wide temperature range from 5 to 120 K. We hope that our results will prove useful for research concerning QCL maximum operating temperatures. Keywords: quantum cascade laser, terahertz range, quantum well, molecular beam epitaxy, activation energy, temperature degradation.

The stimulated emission of Cu(In,Ga)Se2 alloy thin films formed by magnetron-assisted sputtering onto a sodium-fluoride layer deposited onto a molybdenum layer on a glass substrate is observed. The structural and optical parameters of the films are determined by scanning electron microscopy, local X-ray spectral microanalysis, X-ray structural analysis, and low-temperature luminescence (T = 10 K) measurements in the range of excitation levels of 1.6–75 kW cm–2 provided by nanosecond nitrogen-laser pulses. The stimulated emission threshold corresponds to ~25 kW cm–2. Comparative analysis of the emission of Cu(In,Ga)Se2 thin films suggests that the introduction of sodium results in significant improvement of the structural quality, specifically, in a decrease in the density of energy states in the band tails and in a decrease in the concentration of nonradiative-recombination centers.

The incorporation of CdS nanocrystals into a porous ZnO matrix results in sensitization of the composite in the visible spectral region. Studies of the photoconductivity spectra upon variable external illumination show that the spectra undergo reversible transformations. It is shown that the shape of the peak and the position of the local photoconductivity maximum corresponding to nanocrystals depend on the wavelength distribution of the incident radiation intensity. The mechanisms responsible for the process are discussed.

A summary of the 12th Russian Conference on Semiconductor Physics (RCSP-12), September 20–25, 2015, at “Ershovo” hotel near Zvenigorod, Moscow oblast, is presented. The statistics of reports within sections is given, the trends of changing study interests in comparison with the previous 11th Russian Conference on Semiconductor Physics held in 2013 in Saint Petersburg and the 32nd International Conference on Semiconductor Physics held in 2014 in Austin (Texas, USA) are analyzed. The main features of the present conference are indicated, the most interesting lines of research, in my view, are presented.