— Changes in the morphology and structure of the GaAs surface during the deposition of an Au film by thermal evaporation in vacuum have been studied. It has been found that the deposition of an Au film with the participation of a flow of particles and light from a heated evaporator causes the appearance of photoeffects in the near-surface GaAs layers, including light diffraction on surface acoustic waves, the growth of whiskers, and electron emission, which leads to the formation of microcracks on the GaAs surface and the growth of GaAs crystallites. It is shown that the structure and composition of the film boundaries of Au and GaAs surfaces depend on the electron concentration in gallium arsenide, which ultimately determines the properties of the electrophysical parameters of the Au–GaAs contacts.

The possibility of using reagent-free modified water for preparing the GaAs surface in the process of creating microstrip structures with Au-GaAs contacts has been studied. It is shown that, compared with the well-known technique based on the use of deionized water, it is possible to significantly improve the quality of both rectifying and non-rectifying (ohmic) contacts obtained by the thermal evaporation of metals in vacuum. This is achieved by creating a layer of recrystallized gallium arsenide instead of a thin layer of natural oxide at the metal-semiconductor interface.

Active microstrip antennas, or antenna-oscillators (AOs) based on field-effect transistors, make it possible to create small-sized radiation sources in a wide frequency range, including the multi-element arrays with the possibility of power combining. The generation of radiation in the microwave range (5-20 GHz), depending on the conditions, can be single-frequency or multi-frequency, and the generation of noise-like signals was also observed. The combining of the AOs radiation power in the mode of oscillation stochastization is of the specific interest. In contrast to phased arrays, where power summation is achieved under conditions of synchronized monochromatic generators, the interaction of stochastic oscillation generators is a complicated process that leads to a radical change in the overall radiation spectrum. It seems more promising to combine the noise emission spectra and power of independent AOs with adjacent and controlled generation frequencies. In this paper, we study the possibilities to combine the power and emission spectra of a group of AOs, taking into account the possibility of their mutual synchronization.

Microwave solid-state oscillators of noise-like signals are of the great interest for wireless telecommunication systems, imaging systems and electronic warfare. In the paper, the possibility of power combining in the array of three independent noise-like oscillators is investigated. The noise-like oscillators are based on the microstrip log-periodic antennas which are integrated with field-effect transistors. As an active element, NE350184С field-effect transistor with 13.5 dB gain at 12 GHz is chosen. It was previously shown that single-frequency, multifrequency or noise-like generations are possible in the active antennas. The main factors that affect the generation type are the current in the drain-source circuit of the transistor and the distance between the antenna plane and reflecting screen. It is experimentally shown, that using of the noise-like oscillator arrays makes possible the spectrum and power combining, but the construction is not enough stable and reliable.

The GaAs surface is under investigation depending on the methods of preepitaxial processing. It is shown that the known methods of surface treatment using acid or alkaline etchants with subsequent annealing in a vacuum chamber lead to different results in terms of the composition of the near-surface layer. It is found that the physical and chemical properties of water at the stage of neutralization of the etching solution play an important role in the finish washing of GaAs. Moreover, from the remaining drops on the surface of GaAs during the drying stage either a thin layer of GaAs oxide (when using deionized water), or a layer of recrystallized GaAs (when using reagent-free modified water) can precipitate.

The study investigates the possibility of generating noiselike signals in the centimeter wavelength range using antenna generators built on a log-periodic microstrip antenna integrated with a field-effect transistor. The conditions for the occurrence of noiselike generation are experimentally determined. The possibility of expanding the noiselike spectrum using low-frequency noise modulation is studied. Noiselike generation was experimentally obtained in the centimeter wavelength range with a spectral width of up to 2 GHz.

A microwave radiation intensity indicator based on an antenna-coupled detector (rectenna), an amplifier, and a semiconductor light-emitting diode was constructed and tested. This device is a hybrid integrated circuit, where a microstrip log-periodic antenna on a dielectric substrate also serves as a mechanical carrier. The possibility of visual determination of the shape of the antenna radiation pattern and the shape of an object based on the reflected radiation intensity was demonstrated experimentally at 10 and 30 GHz.

ГЕНЕРАЦИЯ ШУМОПОДОБНОГО ИЗЛУЧЕНИЯ СВЧ ДИАПАЗОНА В ОДНОМЕРНОЙ РЕШЕТКЕ МИКРОПОЛОСКОВЫХ АНТЕНН-ГЕНЕРАТОРОВ

The design of a microwave oscillator based on a microstrip log-periodic antenna integrated with a field effect transistor and a waveguide built in a dielectric substrate has been developed and analyzed. The waveguide geometry provides the possibility of propagation and radiation at both the fundamental frequency of the log-periodic antenna and harmonics. Computer simulation of the oscillator design in a frequency range near resonance frequencies of the log-periodic antenna is conducted. The possibility of summation of powers of several antenna–oscillators arranged ias a linear phased array is investigated.

A design of the microstrip antenna with an epitaxial structure used as a dielectric substrate is developed. The epitaxial structure contains a thin layer of n-type gallium arsenide of on a GaAs semi-insulating substrate. The layer thickness is selected with consideration for the carrier depletion region that appears at the interface between the metal layer, which forms the antenna, and the doped semiconductor layer. We demonstrated experimentally the possibility of application of this design as a FET antenna–generator in a frequency range of 10–15 GHz.

We report the growth of gallium arsenide epilayers on the surface of single-crystal NiSb having metallic conduction. The gallium arsenide epilayers were grown by molecular beam epitaxy under conditions typical of the fabrication of homoepitaxial structures. Structural and morphological characterization of the GaAs films showed that the growth process involved a transition from a textured polycrystal to a more ordered layer with a well-defined system of diffraction spots in its electron diffraction pattern, indicative of an epitaxial process.

Effects of locking of generator antennas (GAs) with field-effect transistors by the electromagnetic field formed as a result of reflection of radiation from a semitransparent dielectric mirror are analyzed. The possibility of spatial combining of the radiation powers of the GAs placed on a common dielectric substrate and forming a linear or a 2D matrix is demonstrated. It is shown that application of a reflecting mirror can substantially expand the GA mutual locking band and abandon external locking for power combining in the 2D matrix.

Effects of locking by an external electromagnetic field of an array of oscillator antennas (OAs) designed by field-effect transistors integrated with log-periodic antennas are analyzed. The possibility of spatial combining of the radiation powers of OAs placed on a common dielectric substrate and arranged into a 1D array is demonstrated. It is shown that application of external locking can ensure severalfold broadening of the locking band of an ensemble of independent self-oscillators as compared to the case of mutual locking by a common field propagating in the dielectric substrate.

We study experimentally synchronization and power combining of microwave oscillators containing field-effect transistors as active elements, which are coupled with log-periodic antennas on a dielectric substrate. The possibility of mutual synchronization of antenna-coupled oscillators located on a common dielectric substrate, which is stipulated by their interaction with the surface wave propagating in the substrate, is demonstrated. The possibility of synchronization of antenna-coupled oscillators by external radiation is also studied. Significant narrowing of the spectrum width and an increase in the oscillation efficiency are found.

Mutual synchronization of the oscillations in the linear and two-dimensional arrays of log-periodic antennas on the dielectric substrate with field-effect transistors as active elements is experimentally studied. A dielectric reflector is used for broadening of the synchronization frequency band. The opportunity of effective special power combining in the case of two-dimensional array is shown.

Mutual and external synchronization of the oscillations in the linear array of log-periodic antennas on the dielectric substrate with field-effect transistors as active elements is studied. The opportunity of effective special power combining is experimentally shown.

Power combining in the array of microwave oscillators, consisted of log-periodical antennas with field-effect transistors as active elements, is experimentally studied. The opportunity for considerable improvement of the oscillation efficiency due to the mutual synchronization is shown and conditions of the radiation pattern formation are defined.

Power combining in the array of microwave oscillators, consisted of log-periodical antennas with field-effect transistors as active elements, is experimentally studied. The opportunity for considerable improvement of oscillation efficiency due to the mutual synchronization is shown and conditions of formation of the radiation pattern are defined.