[en] On the basis of Fourier transform infrared (FTIR) spectroscopy, a method is implemented that enables measurements of infrared (IR) photoluminescence with a high reverse duty cycle of pump pulses, which decreases the uncontrolled heating of semiconductor structures by an excitation laser. The method was used to record IR photoluminescence spectra of test narrow-gap low-dimensional heterostructures in the wavelength range of 1–5 µm. It is determined that, at high reverse duty cycles of the reference pulse (greater than 20), the developed gated integration method has a better signal-to-noise ratio in the measured spectra than does the conventionally used synchronous detection (lock-in) method.

[en] The effect of external electric field on interband optical transitions in single In_xGa_1-xAs/GaAs quantum wells is studied by electroreflectance spectroscopy. A procedure is suggested for separating the contribution of particular exciton transitions to the complicated modulation spectrum. Nontrivial field dependences of the probability of optical transitions forbidden by the symmetry are observed experimentally. The data are compared with the corresponding theoretical dependences. The strength of the internal electric field in the region of the quantum well is determined from Frantz-Keldysh's oscillations. Under certain electric fields, the probability of transitions forbidden with no field is higher than the probability of transitions allowed by the symmetry

[en] A photoluminescence (PL) measurement method using boxcar integration in the active baseline subtraction mode has been implemented. It allows for infrared PL measurements with a low duty cycle of the pump pulse, thereby minimizing the uncontrolled heating of the structure under study. The implemented method was compared to phase-sensitive detection by signal-to-noise ratio of the resulting spectra, indicating its superior performance at low duty cycles. The decrease in uncontrolled heating of the structure under study was confirmed by observing a change in the ratio of temperature-sensitive PL peaks of a test InSb/InAs/InGaAs/InAlAs/GaAs nanoheterostructure. (paper)

[en] The results of analyzing the photoluminescence spectra of metamorphic In_0.75Al_0.25As/In_0.05-0.8Al_0.95-0.2As/GaAs heterostructures grown by molecular-beam epitaxy method are presented. In the spectra of low-temperature photoluminescence, three emission peaks have been detected, which correspond to carrier recombination in different areas of the structure. These include a part of the In_0.75Al_0.25As “virtual substrate” grown at high temperature, and the area of a triangular potential well formed by the meta-morphic buffer layer and the “virtual substrate”. Photoluminescence related to defects in the high-temperature part of the “virtual substrate” was also measured. (paper)

[en] The GaAs/AlGaAs superlattice grown by metal-organic chemical vapour deposition (MOCVD) was investigated by photoreflectance (PR) spectroscopy. Optical transitions over the whole band structure were measured at room temperature. Different laser pump beams (632 and 532 nm) were used to clarify the nature of the PR signal formation. Charge carriers transport over minibands was revealed by using long-wave modulation. An acceptable correlation of theoretical and experimental results was achieved for low-energy transitions. Optical transitions relating to the edges of the first and the second minibands for electrons, heavy and light holes were clearly observed experimentally. (paper)

[en] The InSb/AlInSb single quantum well energy spectrum is determined both theoretically and experimentally (from the photoluminescence spectra). The 8-band Kane model is used to take into account the dispersion law nonparabolicity. The mechanical strain is considered by the deformation potentials theory. The photoluminescence measurements were carried out in the 12-160K temperature range and at various excitation powers. All the observed features of the photoluminescence spectra are well described by the theoretical calculations

[en] Photoreflectance (PR) spectra of Al_xIn_1-xSb-based heterostructures have been obtained by using a novel photomodulation Fourier-transform infrared (FTIR) spectroscopy method. The studied samples - bulk Al_xIn_1-xSb epilayers and InSb/Al_xIn_1-xSb heterostructures - were grown by molecular beam epitaxy on semi-insulating GaAs substrates via AlSb buffer layers. The critical-point energies E ₀ and E ₀+Δ₀ of Al_xIn_1-xSb alloys of various direct-gap compositions were defined from the PR spectra features. It was found that the E ₀ values are greater than the observed Al_xIn_1-xSb photoluminescence peak energy, with the difference increasing with x. For the InSb/Al_xIn_1-xSb heterostructures, PR signals corresponding to Franz-Keldysh oscillations in the alloy barrier have been observed. Analysis of their period has allowed one to determine the intensity of the internal electric field in Al_xIn_1-xSb layers. This result enables evaluation of the surface Fermi level pinning, and elucidation of the effect of doping in such heterostructures. (paper)

[en] Photoluminescence (PL) properties of type-II InSb/InAs periodic nanostructures containing above-monolayer (ML)-thick InSb insertions, grown by molecular beam epitaxy, are studied by using an FTIR spectrometer in wide temperature range. The samples exhibit bright PL in the 3.5–5.5 μ m range, which is attributed to recombination of holes localized in InSb with electrons accumulated nearby in the InAs matrix. An increase in the InSb nominal thickness from 1 ML to 1.6 ML results in an increase of the PL peak wavelength up to 5.5 μ m (300 K), and significantly improves luminescence intensity at 300 K due to a twice larger energy of hole localization. The InSb/InAs nanostructures also demonstrate an anomalous ‘blue’ shift of the PL peak energy as the temperature increases in the 12–80 K range, which is attributed to the thermally induced population of localized states in the InSb insertions, emerging due to composition/thickness fluctuations. Sb segregation in the cap InAs barrier smooths the potential inhomogeneities in the insertions, which reduces the broadening parameter. (paper)

[en] Photoluminescence (PL) properties of undoped InAs autoepitaxial layers are studied at various temperatures (9-120 K) and excitation power density (0.2-12.5 W/cm"2). The studied structures have been grown on highly doped n"+"+-InAs substrates by chloride-hydride vapour phase epitaxy method. PL spectra measurements were carried out with an FTIR spectrometer. The samples exhibit several luminescence peaks in the 2.9-3.3 μm range, which are attributed to free exciton transitions, deep donor bound excitons, and donor-acceptor pairs. A correlation is revealed between the PL intensity, and the background doping level of InAs epilayers – as supported by the free carrier concentration and mobility measurements, as well as SIMS data. A decrease of donor-bound exciton PL peak is observed for InAs sulfidized by Na_2S. (paper)

[en] Nanostructures with a submonolayer InSb type-II insertion inside a InAs/InGaAs type-I quantum well (QW) have been grown by molecular beam epitaxy on GaAs (0 0 1) substrates via a convex-graded InAlAs metamorphic buffer layer (MBL). Selection of optimal growth conditions and design of the MBL-virtual substrate system enables one to increase mid-infrared photoluminescence (PL) and internal quantum efficiency (IQE) of the nanoheterostructures. The maximum low temperature IQE of about 90% has been obtained owing to the residual strain engineering which has resulted in both reduction of the extended defect density in the QW, likely responsible for Shockley–Read–Hall non-radiative recombination, and suppression of the Auger recombination channels in the InAs QW and the barriers. Temperature dependence of the integrated PL intensity was analyzed to determine an activation energy of an additional high-temperature non-radiative process (∼49 meV) related presumably to hole delocalization through acceptor states in the strained InAs QW. (paper)