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This paper presents the current status of medium-wave infrared (MWIR) detectors at the Military University of Technology’s Institute of Applied Physics and VIGO System S.A. The metal–organic chemical vapor deposition (MOCVD) technique is a very convenient tool for the deposition of HgCdTe epilayers, with a wide range of compositions, used for uncooled infrared detectors. Good compositional and thickness uniformity was achieved on epilayers grown on 2-in-diameter, low-cost (100) GaAs wafers. Most growth was performed on substrates, which were misoriented from (100) by between 2° and 4° in order to minimize growth defects. The large lattice mismatch between GaAs and HgCdTe required the usage of a CdTe buffer layer. The CdTe (111) B buffer layer growth was enforced by suitable nucleation procedure, based on (100) GaAs substrate annealing in a Te-rich atmosphere prior to the buffer deposition. Secondary-ion mass spectrometry (SIMS) showed that ethyl iodide (EI) and tris(dimethylamino)arsenic (TDMAAs) were stable donor and acceptor dopants, respectively. Fully doped (111) HgCdTe heterostructures were grown in order to investigate the devices’ performance in the 3–5 µm infrared band. The uniqueness of the presented technology manifests in a lack of the necessity of time-consuming and troublesome ex situ annealing.

Existing literature reports on the dependence of phonon properties on temperature rarely use statistical analysis. The lack of uncertainty assessment, which takes into account changes in the parameter value within the sample, substantially hinders comparison among the data reported so far. Moreover, it is impossible to determine whether these results display discrepancies between themselves due to sample- and technology-dependent issues, manifestations of statistical noise, or a deeper cause that has not yet been grasped. Here, we show the distributions of the phonon properties at temperatures in the range of 300 K–500 K, which were used to calculate the temperature derivatives of the phonon energies χ. These can be used in the procedure of the extraction of graphene thermal conductivity κ but are also related to the anharmonic part of the graphene crystal lattice potential and/or nonadiabatic effects. Finally, we show that the correlation analyses revealed the existence of an unknown physical cause of differences between χ values, showing that the thermal properties of phonons in graphene are still not fully understood and further studies on the contribution of doping, stress, defects and interaction with the substrate, including its thermal expansion, are required to explain the observed parameter variability.

The one-port configuration of a microwave device is the simplest architecture for graphene ultrafast (photo-)resistors, (photo-)diodes, sensors, and photodetectors. Here, this configuration is realized by a segment of coplanar waveguide (CPW) loaded with a CVD graphene monolayer shorted to the ground. The magnitude and phase of the reflection coefficient ( ${S}_{11}$ parameter) measured in the $0.1~\div ~26$ GHz frequency range are presented for undisturbed structures as well as for structures illuminated by white light and electrostatically polarized with the backgate. A simple and robust de-embedding procedure based on the signal flow graph and allowing for a simultaneous extraction of the parameters characterizing the CPW segment and the graphene monolayer is proposed. The graphene impedance at microwave frequencies is in good agreement with the value of dc sheet resistance obtained from van der Pauw measurements. The back-gate voltage modulation is an efficient way to modulate both the dc sheet resistance and the impedance. In particular, the Dirac point can be achieved both at microwave frequencies and at dc. An equivalent circuit model consists of only the resistance and capacitance connected in parallel, because of good quality ohmic contacts and a negligible inductance as a result of low-current flow in high-resistance graphene samples.

Measurements of minority carrier lifetime have been carried out on nonintentionally doped HgCdTe(100) layers grown by metal organic chemical vapor deposition on GaAs substrates. The studies have been carried out in order to investigate the possibility of applications of HgCdTe(100) epilayers to fully depleted P–i–N photodiodes operated at near-room temperatures and the background-radiation limit. Post-growth annealed layers show n-type conductivity with a residual donor concentration of about 1015 cm−3. The cadmium molar composition (0.262 < x < 0.336) was chosen for mid-wave infrared devices operating at 230 K to 300 K. Results show that at high temperatures, the samples show clearly Auger-limited lifetimes determined by the background doping. The measured lifetimes at 300 K range from 5 to 11 µs, and from 0.2 to 1 µs, for the cut-offs of 4 µm and 5.4 µm, respectively.

CVD is currently the most popular and widelyused of these techniques, owing to its low cost, good yield,and simple scalability.Among many CVD growth conditions for CNTs, thecarbon precursor is likely to play a crucial role indetermining the structural properties of the final material.Many gaseous precursors, such as methane, acetylene,carbon monoxide, and others, are widely used for high-quality CNT synthesis.

We report on the electrical characterization and Raman spectroscopy of chemical vapor deposition copper-grown graphene transferred onto a Si/SiO2 substrate by high-speed (1 mm/s) electrochemical delamination. We determine graphene’s sheet resistance, carrier mobility, and concentration as well as its physical quality as a function of the electolyte concentration. Graphene’s electrical properties are investigated with standard Hall measurements in van der Pauw geometry and a contactless method that employs a single-post dielectric resonator operating at microwave frequencies. These properties are related to the widely used copper etching technique. The results prove that the high-speed electrochemical delamination provides good-quality graphene within a short time scale.

In this report, we demonstrate the preparation method of a multi-layer stack with a pre-defined number of graphene layers, which was obtained using chemical vapor deposition graphene deposited on a copper substrate and subsequently transferred onto a poly(methyl methacrylate) (PMMA) substrate. The prepared multi-layer stack can also be transferred onto an arbitrary substrate and in the end, the polymer can be removed, which in consequence significantly increases the range of possible graphene applications. The multi-layer character was confirmed by optical transmittance measurements and Raman spectroscopy, whereas the microstructure of the multi-layer graphene stack was investigated using Scanning Electron Microscopy. The electrical properties in the function of the number of graphene layers were assessed with standard Hall Effect measurements. Finally, we showed the practical application of the multi-layer graphene stack as a saturable absorber of a mode-locked Er-doped fiber laser.

In this paper we study graphene synthesized on undoped (001), (110), and (111) Ge substrates, and show how the surface orientation and reconstruction affect its morphological and structural properties. The article presents the first attempt to explain the impact of germanium surface reconstruction on the shape and the density of graphene nuclei as well as on the material's stress and doping levels. Our findings suggest that graphene obtained on Ge(001) is the most uniform, with low doping (1.5 × 1012 cm−2) and low strain level (−0.1%). Graphene on Ge(110) appears to be highly compressed (−0.5%) while graphene on Ge(111) exhibits doping reaching 5 × 1013 cm−2. These results help to better understand the dynamics of graphene growth on germanium and indicate Ge(001), in terms of its structural properties, as the most promising orientation for the future CMOS applications.