We report stimulated emission in 2.8 - 3.5 um wavelength range from HgTe/CdHgTe quantum well (QW) heterostructures grown on GaAs substrates at temperatures available with thermoelectric cooling. The structures were designed to suppress the Auger recombination by implementing narrow (1.5 - 2 nm wide) QWs. We conclude that Peltier cooled operation is feasible in lasers based on such structures, making them of interest for spectroscopy applications in the atmospheric transparency window from 3 to 5 um. This work aims to demonstrate that the potential of MCT structures for mid-infrared lasers in not exhausted.

We study plasmonic properties of highly doped InP in the mid-infrared (IR) range. InP was grown by metal-organic vapor phase epitaxy (MOVPE) with the growth conditions optimized to achieve high free electron concentrations by doping with silicon. The permittivity of the grown material was found by fitting the calculated infrared reflectance spectra to the measured ones. The retrieved permittivity was then used to simulate surface plasmon polaritons (SPPs) propagation on flat and structured surfaces, and the simulation results were verified in direct experiments. SPPs at the top and bottom interfaces of the grown epilayer were excited by the prism coupling. A high-index Ge hemispherical prism provides efficient coupling conditions of SPPs on flat surfaces and facilitates acquiring their dispersion diagrams. We observed diffraction into symmetry-prohibited diffraction orders stimulated by the excitation of surface plasmon-polaritons in a periodically structured epilayer. Characterization shows good agreement between the theory and experimental results and confirms that highly doped InP is an effective plasmonic material aiming it for applications in the mid-IR wavelength range.

Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors.

We report on the voltage response of carbon nanotube devices to sub-terahertz (THz) radiation. The devices contain carbon nanotubes (CNTs), which are over their length partially suspended and partially Van der Waals bonded to a SiO2 substrate, causing a difference in thermal contact. We observe a DC voltage upon exposure to 140 GHz radiation. Based on the observed gate voltage and power dependence, at different temperatures, we argue that the observed signal is both thermal and photovoltaic. The room temperature responsivity in the microwave to THz range exceeds that of CNT based devices reported before.

Red/near-infrared photoluminescence (PL) of silicon irradiated by ions for wide dose range is investigated. The results are presented obtained for doses near amorphization threshold, where PL is associated with the formation of composite structure composed of nanocrystals (quantum dots) embedded into amorphized matrix and for doses that are strongly larger than amorphization threshold. The PL in this case is caused by formation of nanocrystals due to recrystallization of amorphous layer and penetration of stresses behind the border of this layer.

The effects of bias voltage and cladding layer thickness on the surface photovoltage in the semiconductor/electrolyte system (PSE) of InAs/GaAs quantum dot (QD) structures grown by atmospheric-pressure metal organic vapour phase epitaxy have been investigated. It was shown that the effect of compensation of the normal component of the photovoltage by the lateral component in the structures with an asymmetric point ohmic contact may help to reveal details of the energy spectrum of the QDs. Using this effect, it was shown that emission of electrons and holes from the QDs to the barrier at strong electric field occurs directly from the excited levels, without relaxation to the ground state. The observed broadening of the optical transition lines in QDs in a strong electric field was related to the lifetime of the carriers in the excited levels in QDs, according to the uncertainty relation. The lifetime of the carriers in QDs was limited by the carrier emission rate from QDs to the matrix through a triangle barrier at strong electric field. The possibility of in situ investigation of the processes of formation and passivation of the surface traps resulting from electrochemical reactions in the electrolytic cell by PSE spectroscopy has been demonstrated.

The photovoltaic effect in the semiconductor/electrolyte junction is an effective method for investigation of the energy spectrum of InAs/GaAs heterostructures with self-assembled quantum dots. An important advantage of this method is its high sensitivity. This makes it possible to obtain photoelectric spectra from quantum dots with high barriers for the electron and hole emission from quantum dots into the matrix even if the surface density of the dots is low (∼10 9 cm −2 ). In a strong transverse electric field, broadening of the lines of optical transitions and emission of electrons and holes from quantum dots into the matrix directly from the excited states are observed. The effect of the photovoltage sign reversal was detected for a sufficiently high positive bias across the barrier within the semiconductor. This effect is related to the formation of a positive charge at the interface between the cap layer and electrolyte and of the negative charge on impurities and defects in the quantum dot layer.

A comparative study of the surface morphology, photoluminescence, and photoelectric spectra of heterostructures with InAs/GaAs quantum dots (QDs) grown on the surface, uncovered by etching away the cladding layer, and built in the GaAs matrix is reported. The red-shift of the ground transition energy in the surface QDs compared to the built-in ones has been shown to be related not only to relaxation of the elastic strain, but also to the differences in size, shape, and chemical composition of the nanoclusters. The method of photoelectric spectroscopy in a semiconductor/electrolyte system has been applied to monitor the process of etching of the cladding layer in situ. Using this method, controlled uncovering of the buried QDs was shown to be possible. In turn, this makes it possible to study the actual morphology of the buried quantum-size layers by atomic force microscopy.

Doping of InAs quantum dots during growth by Metal Organic Chemical Vapor Deposition by Bi depresses coalescence of the nanoclusters and improves the uniformity of the quantum dot size distribution, By this method the quantum dot structures emitting at 1.46 mum at room temperature with the emission linewidth as narrow as 25 meV have been obtained.