The inductively coupled plasma reactive ion etching (ICP-RIE) is a selective dry etching method used in fabrication technology of various semiconductor devices. The etching is used to form non-planar microstructures—trenches or mesa structures, and tilted sidewalls with a controlled angle. The ICP-RIE method combining a high finishing accuracy and reproducibility is excellent for etching hard materials, such as SiC, GaN or diamond. The paper presents a review of silicon carbide etching—principles of the ICP-RIE method, the results of SiC etching and undesired phenomena of the ICP-RIE process are presented. The article includes SEM photos and experimental results obtained from different ICP-RIE processes. The influence of O₂ addition to the SF₆ plasma as well as the change of both RIE and ICP power on the etching rate of the Cr mask used in processes and on the selectivity of SiC/Cr etching are reported for the first time. SiC is an attractive semiconductor with many excellent properties, that can bring huge potential benefits thorough advances in submicron semiconductor processing technology. Recently, there has been an interest in SiC due to its potential wide application in power electronics, in particular in automotive, renewable energy and rail transport.

We present an extensive study of resonant two-dimensional (2D) plasmon excitations in grating-gated quantum well heterostructures, which enable an electrical control of periodic charge carrier density profile. Our study combines theoretical and experimental investigations of nanometer-scale $\mathrm{AlGaN}/\mathrm{GaN}$ grating-gate structures and reveals that all terahertz (THz) plasmonic resonances in these structures can be explained only within the framework of the plasmonic crystal model. We identify two different plasmonic crystal phases. The first is the delocalized phase, where THz radiation is absorbed with the entire grating-gate structure that is realized at a weakly modulated 2D electron gas (2DEG) regime. In the second, the localized phase, THz radiation interacts only with the ungated portions of the structure. This phase is achieved by fully depleting the gated regions, resulting in strong modulation. By gate controlling of the modulation degree, we observe a continuous transition between these phases. We also discover that, unexpectedly, the resonant plasma frequencies of ungated parts (in the localized phase) still depend on the gate voltage. We attribute this phenomenon to the specific depletion of the conductive profile in the ungated region of the 2DEG, the so-called edge gating effect. Although we study a specific case of plasmons in $\mathrm{AlGaN}/\mathrm{GaN}$ grating-gate structures, our results have a general character and are applicable to any other semiconductor-based plasmonic crystal structures. Our work represents the first demonstration of an electrically tunable transition between different phases of THz plasmonic crystals, which is a crucial step toward a deeper understanding of THz plasma physics and the development of all-electrically tunable devices for THz optoelectronics.

The fabrication processes for silicon nitride photonic integrated circuits evolved from microelectronics components technology—basic processes have common roots and can be executed using the same type of equipment. In comparison to that of electronics components, passive photonic structures require fewer manufacturing steps and fabricated elements have larger critical dimensions. In this work, we present and discuss our first results on design and development of fundamental building blocks for silicon nitride integrated photonic platform. The scope of the work covers the full design and manufacturing chain, from numerical simulations of optical elements, design, and fabrication of the test structures to optical characterization and analysis the results. In particular, technological processes were developed and evaluated for fabrication of the waveguides (WGs), multimode interferometers (MMIs), and arrayed waveguide gratings (AWGs), which confirmed the potential of the technology and correctness of the proposed approach.

In optical communication and sensing, silicon nitride (SiN) photonics plays a crucial role. By adeptly guiding and manipulating light on a silicon-based platform, it facilitates the creation of compact and highly efficient photonic devices. This, in turn, propels advancements in high-speed communication systems and enhances the sensitivity of optical sensors. This study presents a comprehensive exploration wherein we both numerically and experimentally display the efficacy of a SiN-based ring resonator designed for refractive index sensing applications. The device’s sensitivity, numerically estimated at approximately 110 nm/RIU, closely aligns with the experimental value of around 112.5 nm/RIU. The RR sensor’s Q factor and limit of detection (LOD) are 1.7154 × 10⁴ and 7.99 × 10⁻⁴ RIU, respectively. These congruent results underscore the reliability of the two-dimensional finite element method (2D-FEM) as a valuable tool for accurately predicting and assessing the device’s performance before fabrication.

This paper investigates the wavelength-dependent sensitivity of a ridge waveguide based on a silicon nitride (Si₃N₄) platform, combining numerical analysis and experimental validation. In the first part, the modal characteristics of a Si₃N₄ ridge waveguide are analyzed in detail, focusing on the effective refractive index (n_eff), evanescent field ratio (EFR), and propagation losses (α_prop). These parameters are critical for understanding the interplay of guided light with the surrounding medium and optimizing waveguide design for sensing applications. In the second part, the wavelength-dependent sensitivity of a racetrack ring resonator (RTRR) based on the Si₃N₄ waveguide is experimentally demonstrated. The results demonstrate a clear increase in the sensitivity of the RTRR, rising from 116.3 nm/RIU to 143.3 nm/RIU as the wavelength shifts from 1520 nm to 1600 nm. This trend provides valuable insights into the device’s enhanced performance at longer wavelengths, underscoring its potential for applications requiring high sensitivity in this spectral range.