Резонансная микроволновая спектроскопия полупроводников с микронным разрешением

We have proposed and experimentally verified a local method of microwave resonant spectroscopy of semiconductors. The microwave circuit of the spectrometer based on the Cascade Microtech probe station is equipped with a coaxial resonator of special geometry. As result, the measurement accuracy of the previously developed volt-impedance spectroscopy method was greatly increased. A technique for spectrometer calibration and resonant measurements of the complex impedance of the probe-sample system has been developed. We have measured the impedance of test structures with Schottky contacts of 30 - 60 μm in diameter on a single-crystal GaAs wafer at several discrete frequencies in the range of 50 - 250 MHz. The nontrivial resistive properties of the structures are studied, which consist of the excess resistance that is 1–2 orders higher than the spreading resistance for the alternating current in the unperturbed region of the semiconductor. The discovered effect is presumably associated with the a.c. charge modulation on deep levels of the semiconductor. A model calculation of the impedance spectrum has been performed, which demonstrates a good agreement with the experimental spectra.

Photonic and terahertz applications as a next driver of gallium arsenide market

Analysis of current GaAs and related device market initiated in a number of earlier works has been continued. Binary semiconductor GaAs compound is a conventional MW electronics material. Until recently GaAs based HF ICs for mobile phones were among the most rapidly growing segments of GaAs market. However the GaAs market development trend is changing. Photonics and TeraHertz engineering are becoming the new world GaAs market drivers. This means that the current emphasize of GaAs single crystal technologies will shift toward vertical directional crystallization of “optoelectronic quality” crystals. In the medium and longer terms the world GaAs wafer and epitaxial structure markets will continue growing. In the shorter term we all will have to take into account COVID epidemic consequences. Still the GaAs market is closely related to Smartphone market novelties. Quite probably after a long growth period the GaAs market will keep on shrinking for the second consecutive year: GaAs production may decline by 11–12 % in 2020. Assuming that the epidemic will be somehow taken under control in 2021 the overall Smartphone production can probably be expected to grow starting from 2021.Currently the Russian market of semiconductor compounds for photonics and electronic components (GaAs etc.) is but moderate and in predictable terms is not expected to achieve a level that is required for the emergence of a competitive domestic manufacturer, even though all importation replacement programs are accomplished. Meanwhile there is understanding that developing an advanced electronic components industry in Russia requires larger production of source materials.

Photonic and Terahertz applications as the next gallium arsenide market driver

Analysis of current GaAs and related device market initiated in a number of earlier works has been continued. Binary semiconductor GaAs compound is a conventional MW electronics material. Until recently GaAs based HF ICs for mobile phones were among the most rapidly growing segments of GaAs market. However the GaAs market development trend is changing. Photonics and Terahertz engineering are becoming the new world GaAs market drivers. This means that the current emphasize of GaAs single crystal technologies will shift toward vertical directional crystallization of “optoelectronic quality” crystals. In the medium and longer terms the world GaAs wafer and epitaxial structure markets will continue growing. In the shorter term we all will have to take into account COVID epidemic consequences. Still the GaAs market is closely related to Smartphone market novelties. Quite probably after a long growth period the GaAs market will keep on shrinking for the second consecutive year: GaAs production may decline by 11–12% in 2020. Assuming that the epidemic will be somehow taken under control in 2021 the overall Smartphone production can probably be expected to grow starting from 2021. Currently the Russian market of semiconductor compounds for photonics and electronic components (GaAs etc.) is but moderate and in predictable terms is not expected to achieve a level that is required for the emergence of a competitive domestic manufacturer, even though all importation replacement programs are accomplished. Meanwhile there is understanding that developing an advanced electronic components industry in Russia requires larger production of source materials.

Recovery of Gallium from Simulated GaAs Waste Etching Solutions by Solvent Extraction

Gallium arsenide is used in semiconductor industries worldwide. Numerous waste etching solutions are produced during the processes of GaAs wafer production. Therefore, a complete and eco-friendly technology should be established to recover gallium as a gallium chloride solution and remove arsenic ion from waste GaAs etching solution. In this study, the gallium trichloride and arsenic trisulfide powders were dissolved in ammonia solutions to prepare the simulated solutions, and the pH value was adjusted to pH 2 by nitric acid. In the extraction step, the GaAs etching solutions were extracted using 0.5 M Cyanex 272 solutions in kerosene at pH 2 and 0.1 O/A ratio for 5 min. The extraction efficiency attained 77.4%, which had an optimal ratio of concentration, and the four steps extraction efficiency attained 99.5%. After extraction, iron sulfate heptahydrates were added into the raffinate, and the arsenic ions were precipitated. The removed rate attained 99.9% when the Fe/As ratio was 10. In the stripping step, the organic phase was stripped with 0.5 M hydrochloric acid at 1 O/A ratio for 3 min, and 97.5% gallium was stripped. Finally, the purity of gallium chloride solution was 99.95% and the gallium was seven times the concentration of the etching solutions.

GaAs wafers possessing facet-dependent electrical conductivity properties

Current-rectifying I–V curves have been recorded for {110}/{111} facet combination of a GaAs wafer, suggesting the fabrication of facet-controlled transistors.

Особенности газофазной эпитаксии GaAs на непланарных подложках

The features of the surface shape of GaAs epitaxial layers grown on grooves several micrometers wide with vertical walls and an aspect ratio close to unity are investigated. The grooves are formed on the surface of a GaAs wafer in a plasma-chemical etching installation and overgrown by organometallic vapor-phase epitaxy under reduced pressure in a reactor.

THE CURRENT–VOLTAGE CHARACTERISTICS OVER THE MEASUREMENT TEMPERATURE OF 60–400 K IN THE Au/Ti/n-GaAs CONTACTS WITH HIGH DIELECTRIC HfO2 INTERFACIAL LAYER

The Au/Ti/HfO2/[Formula: see text]-GaAs metal/insulating layer/semiconductor structures have been fabricated using standard thermal atomic layer deposition. We experimentally showed whether or not the HfO2 interfacial layer grown on the [Formula: see text]-GaAs wafer modifies the barrier height (BH) of the device at the room temperature. Besides, we investigated the measurement based on temperature dependence of the device parameters from the current–voltage ([Formula: see text]–[Formula: see text]) characteristics of the diode in 60–400[Formula: see text]K range with steps of 10[Formula: see text]K. The X-ray photoelectron spectroscopy (XPS) have been carried out to characterize the surfaces of both [Formula: see text]-GaAs wafer and HfO2 thin films. The series resistance value from the temperature-dependent [Formula: see text]–[Formula: see text] characteristics decreased with decreasing temperature, which is a desired positive result for the devices developed from the MOS capacitor. The BH value of 0.94[Formula: see text]eV (300[Formula: see text]K) has been obtained for the device with the HfO2 layer which is a higher value than the value of 0.77[Formula: see text]eV (300[Formula: see text]K) of the device without HfO2 layer. Therefore, we can say that the HfO2 thin layer at the metal/GaAs interface can also be used for the BH modification as a gate insulator for GaAs MOS capacitor and MOSFETs. When the temperature-dependent [Formula: see text]–[Formula: see text] characteristics at low temperatures have been considered, it has been observed that the current prefers to flow through the lowest BHs due to the BH inhomogeneities.

Arrival timing diagnostics at a soft X-ray free-electron laser beamline of SACLA BL1

An arrival timing monitor for the soft X-ray free-electron laser (XFEL) beamline of SACLA BL1 has been developed. A small portion of the soft XFEL pulse is branched using the wavefront-splitting method. The branched FEL pulse is one-dimensionally focused onto a GaAs wafer to induce a transient reflectivity change. The beam branching method enables the simultaneous operation of the arrival timing diagnostics and experiments. The temporal resolution evaluated from the imaging system is ∼22 fs in full width at half-maximum, which is sufficient considering the temporal durations of the soft XFEL and the optical laser pulses.