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The effect of atomic composition on the rate of the plasma-chemical etching of silicon nitride in high-power transistors based on an AlGaN/GaN heterojunction is studied. It is shown how the subsequent process of its plasma-chemical etching depends on the configuration of the incorporation of hydrogen impurity atoms into the molecular structure of silicon nitride deposited in the plasma. The dependence of the etching rate on the process parameters (the working pressure in the chamber, the plasma-generator power, the working-gas flows, and the deposition temperature) is investigated. It is shown that the etching rate of the HxSirNzHy film is independent directly on the hydrogen content but significantly depends on the ratio of [Si–H]/[N–H] bonds. The etching rate of HxSirNzHy in high-density plasma at low powers is much less dependent on the configuration of hydrogen bonds than the etching rate of this dielectric in a buffer etchant.

Dependence of the chemical composition of a film of plasma-chemical silicon nitride on the technological parameters of the deposition process is studied. The stages in which the process parameters are optimized in order to improve the masking properties of the film are described. A systematic study of the Fourier-transform infra-red (IR) spectra of plasma-chemical silicon-nitride films is carried out. It is found that the chemical resistance of a silicon-nitride film depends on the configuration in which hydrogen is incorporated into chemical bonds.

Performance of a detector based on AlGaAs/InGaAs/GaAs-material system was studied. The detector was comprised of large serpentine array of high-electron mobility transistors (HEMTs) connected in series. The floating drain contact of each transistor (except the last one) served as a source for the next one. Detection of terahertz (THz) radiation was based on the excitation of electron plasma oscillations in the HEMT's channel. The peculiarities of THz response of the detector in question including an enhanced noise-equivalent power were demonstrated.

In terahertz (THz) detectors, based on the excitation of electron plasma oscillations in the two-dimensional electron gas (2DEG) channel, the incident electromagnetic wave is repeatedly reflected between the metal-coated back surface of the GaAs substrate and top surface of the detector. Under certain conditions, a standing terahertz (THz) wave can be established. Placement of the 2DEG in the antinode of the standing wave can result in strong absorption of the detecting THz radiation as we confirmed by analytical calculations and experimental measurements of frequency dependences of THz reflection and absorption coefficients. Effects of the metal bus connecting the fingers of the grating-gate and thickness of the GaAs substrate on the performance of the THz detector were studied as well. It was demonstrated that the spatial separation of the gate fingers from bus metallization by the mesa resistor resulted in the enhanced photoresponse of the detector.In terahertz (THz) detectors, based on the excitation of electron plasma oscillations in the two-dimensional electron gas (2DEG) channel, the incident electromagnetic wave is repeatedly reflected between the metal-coated back surface of the GaAs substrate and top surface of the detector. Under certain conditions, a standing terahertz (THz) wave can be established. Placement of the 2DEG in the antinode of the standing wave can result in strong absorption of the detecting THz radiation as we confirmed by analytical calculations and experimental measurements of frequency dependences of THz reflection and absorption coefficients. Effects of the metal bus connecting the fingers of the grating-gate and thickness of the GaAs substrate on the performance of the THz detector were studied as well. It was demonstrated that the spatial separation of the gate fingers from bus metallization by the mesa resistor resulted in the enhanced photoresponse of the detector.

In this paper we develop an analytical model for the light-emitting diode (LED) with the metal p-contact patterned as an array of thin strips. The model is based on conformal mapping approach and accounts for the overlapped fringing electric fields created by the adjacent strips. We derive analytical expressions for the electric potential, current injected into the LED active region and power of light extracted via the openings in the pattern. Spatial distribution of electric potential and LED radiation pattern are calculated. Further investigations are necessary to elucidate the contribution of the side walls of the strips on the LED output performance.

Impact of mesh-like top metal electrode on output performance of light-emitting diode (LED) is studied using developed numerical model. Three-dimensional Laplace equation is solved by FEM method. Modeling results demonstrate that effect of mesh pitch variation dominates over strip height variation.

Light-emitting diode (LED) with nonuniform current injection caused by the mesh-like design of top metal electrode is studied numerically. Three-dimensional Laplace equation for electric potential is solved by finite element method. The numerical model incorporates mapped infinite element to account for potential decay far away from the LED structure and finite element model developed for boundary condition at semiconductor-air interface in the mesh opening. Simulation results demonstrate the effect of the mesh geometrical parameters on the total output power.

An analytical model of a resonant micro-electromechanical system (MEMS) with a high-electron mobility transistor (HEMT)-like structure and an array of resonant cantilevers over its two-dimensional electron gas (2DEG) channel is developed. To account for impact of fringing, spatial distributions of the electric field and sheet electron density at the surface of the HEMT channel are calculated in parametric form. Resistance of the 2DEG channel and frequency-dependent ac amplitude of the source–drain current are derived. The developed model allows evaluation of impact of fringing electric field on output source–drain current for any different number of cantilevers in the array at different spacing between them and can be used for device optimization.

We develop an analytical model for the resonant MEMS with electrical readout in which electrostatically actuated micromachined cantilever oscillates over the two-dimensional electron gas (2DEG) channel and controls the current flowing along it. The model accounts for the impact of electric field fringing on spatial distribution of sheet electron density along the 2DEG channel. Nonuniform spatial distribution of sheet electron density results in distributed resistance of the 2DEG channel. Amplitude of the ac component of the source-drain current is evaluated and compared with that one estimated using ideal model without fringing. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The paper addresses a resonant sensor with array of micromachined cantilevers oscillating over the channel of highelectron-mobility transistor (HEMT)-like structure and controlling source-drain current flowing along it. Electrical readout is realized by direct modulation of the electric current by vibrating cantilevers. Simple analytical model accounting for the impact of electric field fringing on the output performance of the resonant sensor under consideration is developed.

Light-emitting diode (LED) with designed metal electrode to the top p-semiconductor layer is studied. Original numerical model and procedure are developed for the LED with nonuniform distributions of electrical and optical characteristics caused by the mesh-like configuration of the top electrode. The proposed approach can be used to optimize the LED ouput optical performance by proper choice of the geometrical parameters of the meshed electrode.

Light-emitting diodes (LEDs) with patterned metal electrode to the top p-semiconductor layer resulting in enhanced light extraction are studied. Analytical model which includes an efficient procedure for numerical calculation of light extraction under nonuniform current injection caused by contact patterning is developed and used for modeling of two-dimensional spatial distributions of potential, injected current and output optical power.

THz response of AlGaAs/InGaAs/GaAs HEMT structure has been investigated. The structure consists of the serpentine chain of series connected HEMTs. The source of one is the drain for the subsequent transistor. Experiments have been showed THz response peculiarities of such structures and enhanced noise equivalent power.

We develop an analytical and numerical model for performing simulation of light extraction through the planar output interface of the light-emitting diodes (LEDs) with nonuniform current injection. Spatial nonuniformity of injected current is a peculiar feature of the LEDs in which top metal electrode is patterned as a mesh in order to enhance the output power of light extracted through the top surface. Basic features of the model are the bi-plane computation domain, related to other areas of numerical grid (NG) cells in these two planes, representation of light-generating layer by an ensemble of point light sources, numerical "collection" of light photons from the area limited by acceptance circle and adjustment of NG-cell areas in the computation procedure by the angle-tuned aperture function. The developed model and procedure are used to simulate spatial distributions of the output optical power as well as the total output power at different mesh pitches. The proposed model and simulation strategy can be very efficient in evaluation of the output optical performance of LEDs with periodical or symmetrical configuration of the electrodes.