Photoluminescence in a double heterostructure based on a ternary InAsSb solid solution was observed in the mid-infrared range of 2.5–4 μm. A range of compositions of the InAs_1−ySb_y ternary solid solution has been established, where the energy resonance between the band gap and the splitting-off band in the valence band of the semiconductor can be achieved. Due to the impact of nonradiative Auger recombination processes, different temperature dependence of photoluminescence intensity was found for the barrier layer and the narrow-gap active region, respectively. It was shown that efficient high-temperature photoluminescence can be achieved by suppressing the nonradiative Auger recombination (CHHS) process. Increased temperature, for which the energy gap is lower than the split-off band energy, leads to violation of the resonance condition in narrow gap antimonide compounds, which explains the observed phenomenon. This finding might influence future application of the investigated material systems in mid-infrared emitters used for, e.g., optical gas sensing.

We present an optical spectroscopy analysis of the molecular beam epitaxy-grown InAs/GaSb quantum systems to study the higher-order optical transitions in InAs/GaSb superlattices (SLs). We have investigated two type-II SL structures with different layer widths: $\mathrm{In}{\mathrm{As}}_{8\mathrm{ML}}/\mathrm{Ga}{\mathrm{Sb}}_{8\mathrm{ML}}$ and $\mathrm{In}{\mathrm{As}}_{10\mathrm{ML}}/\mathrm{Ga}{\mathrm{Sb}}_{10\mathrm{ML}}$. To experimentally determine the spectral distribution of the higher-order transitions, the Fourier-transformed photoluminescence and Fourier-transformed photomodulated reflectance measurements were used. These measurements were undertaken vs temperature and incident polarization of the probing beam. Complementary theoretical calculations based on the eight $\mathbf{k}·\mathbf{p}$ formalism were also performed to identify the electron and heavy and light hole energy band ladder. Polarization-dependent measurements indicated the interchanging nature of the light and heavy hole states for the second and third valence band vs the SL wave vector $\left(k_z\right)$ along the growth direction. The results were compared with other calculations based on different models and existing experimental results, then summarized and reviewed for possible numerical parameters application ranges in the interface modeling.

We present an experimental study on the optical quality of InAs/InP quantum dots (QDs). Investigated structures have application relevance due to emission in the 3rd telecommunication window. The nanostructures are grown by ripening-assisted molecular beam epitaxy. This leads to their unique properties, i.e., low spatial density and in-plane shape symmetry. These are advantageous for non-classical light generation for quantum technologies applications. As a measure of the internal quantum efficiency, the discrepancy between calculated and experimentally determined photon extraction efficiency is used. The investigated nanostructures exhibit close to ideal emission efficiency proving their high structural quality. The thermal stability of emission is investigated by means of microphotoluminescence. This allows to determine the maximal operation temperature of the device and reveal the main emission quenching channels. Emission quenching is predominantly caused by the transition of holes and electrons to higher QD’s levels. Additionally, these carriers could further leave the confinement potential via the dense ladder of QD states. Single QD emission is observed up to temperatures of about 100 K, comparable to the best results obtained for epitaxial QDs in this spectral range. The fundamental limit for the emission rate is the excitation radiative lifetime, which spreads from below 0.5 to almost 1.9 ns (GHz operation) without any clear spectral dispersion. Furthermore, carrier dynamics is also determined using time-correlated single-photon counting.

We present the results of Fourier-transform measurements for determination of refractive indices of four semiconductor alloys in the midinfrared spectral range from 10 to 300 K. We investigate double-sided-polished, undoped $\mathrm{In}\mathrm{P}$ and $\mathrm{Ga}\mathrm{As}$ substrates as well as ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}/\mathrm{In}\mathrm{P}$ and $\mathrm{Al}\mathrm{As}/\mathrm{Ga}\mathrm{As}$ distributed Bragg reflector (DBR) mirrors with their operational wavelength designed for 4 µm. Through analysis of measured transmittance spectra supported by ellipsometry it is possible to determine the temperature-dependent refractive indices of $\mathrm{In}\mathrm{P}$ and $\mathrm{Ga}\mathrm{As}$ from 1.3 to 11 µm. Furthermore, by using reflectivity measurements supported by numerical modeling of the two types of designed DBR structures the refractive indices of ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}$ and $\mathrm{Al}\mathrm{As}$ for around 4 µm are determined with their temperature dependencies. Data acquired through this method could lead to improvement of already existing optical semiconductor devices expanding their application for longer wavelengths.

We report the optical properties of GaSbBi layers grown on GaSb (100) substrates with different bismuth contents of 5.8 and 8.0% Bi. Fourier-transform photoluminescence spectra were determined to identify the band gaps of the studied materials. Further temperature- and power-dependent photoluminescence measurements indicated the presence of localized states connected to bismuth clustering. Finally, time-resolved photoluminescence measurements based on single-photon counting allowed the determination of characteristic photoluminescence decay time constants. Because of the increasing bismuth content and clustering effects, an increase in the time constant was observed.

Highly transparent and conductive electrodes operating in the infrared (IR) are critically needed for a broad range of technologies, including light-emitting diodes, lasers and photodetectors, which are key building blocks of infrared cameras, LiDARs, and thermal systems such as IR heaters. While transparent conductive electrodes (TCEs) have seen substantial progress in the visible spectrum, their performance in the IR remains limited due to increased absorption and reflection caused by the plasma resonance of free carriers in conductive materials. Here, we demonstrate a large-area TCE based on a metal-integrated monolithic high-contrast grating (metalMHCG) fabricated on a GaAs substrate. This structure acts as an effective antireflection coating, achieving near-unity transmission of unpolarized mid- to far-infrared (M-FIR) light. The metalMHCG exhibits 94% transmission at a wavelength of 7 μm, corresponding to 135% relative to transmission through a flat GaAs–air interface, while maintaining an exceptionally low sheet resistance of 2.8 Ωsq ⁻¹ . By simultaneously delivering excellent optical transparency and electrical conductivity, the metalMHCG establishes a new performance benchmark among M-FIR TCEs and provides a versatile platform for next-generation high-power optoelectronic devices.