Рассмотрена новая микросхема приемопередатчика для интерфейса RS 485 компании АО «ПКК Миландр» – К5559ИН86SI. Приведена информация о характеристиках и особенностях данной микросхемы.

© Introduction GaN heteroepitaxial layers grown on Al2O3 substrates are widely used in blue-light optoelectronic devices. The challenge of development blue-light emitting lasers and high power optoelectronic devices requires improved control of diffusion processes taking place in GaN. Due to a large lattice mis t between the sapphire and GaN, a high density of so-called “threading dislocations” is present in the GaN. The fast diffusion along dislocation leads to deterioration of electrical contacts to GaN, thus limiting the lifetime of GaN based lasers. There are practically no quantitative data about diffusion in GaN. One of the reasons is the technical dif culty of carrying out such diffusion annealings: diffusion in GaN in conditions of thermodynamic stability at temperatures 1000 C and above must be studied under nitrogen overpressure of 1 GPa or more. On the other hand it is known that diffusion of impurities in GaAs and other III-V compounds can cause generation of voids [1]. It can therefore be expected that diffusion of metals will lead to formation of defects in GaN as well. The purpose of the present work was to investigate the diffusion of selected metals, such as Au, Mg and Zn, from evaporated layers into heteroepitaxial GaN layers and to characterize the microstructure after the diffusion anneals. Au was selected as one of the components for electrical contacts to GaN, and a non-reactive metal suitable for basic studies of diffusion processes. Zn and Mg diffusion is of interest since both metals are p-dopants in GaN.

Mechanically alloyed in situ nano Al3Ti dispersed Al50Ti40Si10 amorphous matrix alloy powder was consolidated by hot isostatic pressing in the temperature range of 300–600°C with a pressure of 1.2GPa and holed at this temperature for 10min. Microstructural and phase evolution studies of the mechanically alloyed powder and sintered compacts were conducted by X-ray diffraction and transmission electron microscopy. Alloy sintered at 500°C recorded an excellent combination of high hardness (8.61GPa), compressive strength (1212MPa) and Young's modulus (149GPa). Furthermore, these results have been compared with that of earlier studies based on conventional sintering (CCS), and high pressure sintering (HPS).

The possibility of fabrication of bulk amorphous Ni59Zr20Ti16Sn5 alloy by hot isostatic pressing of powders was investigated. The amorphous powders were obtained by ball milling of amorphous melt spun ribbon and by mechanical alloying of a mixture of powders of pure crystalline elements. Fully amorphous bulk samples were successfully obtained by hot isostatic pressing of both types of powders. However, at least 10% porosity of the sample fabricated from the ball milled ribbon was observed. Further optimisation of the compaction process needs to be performed.

The possibility of fabrication of bulk amorphous Ni59Zr20Ti16Si5 (numbers indicate at.%) alloy by hot isostatic compaction of powders was investigated. The amorphous powders were obtained by ball milling of amorphous melt spun ribbon and by mechanical alloying of a mixture of powders of pure crystalline elements. The as-milled and hot-pressed samples were examined by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Fully amorphous bulk samples were successfully obtained by consolidating the ball milled amorphous ribbon, while compaction of mechanically alloyed powders resulted in partial crystallization of the alloy. Simultaneously, according to microscopy observations, the porosity of the last sample was lower than the one prepared from the ball milled ribbon. The obtained results testify the further optimisation of compaction parameters is needed.

Electrical, thermo-electrical and thermo-mechanical properties were compared for PtSi, aluminum (Al, PtSi–Al, PtSi–AlCuSi, PtSi–TiW–AlCuSi), and copper based contacts (TiW–Ni–Cu, TiW–Ni–Cu–Ni–Au, PtSi–TiW–Ni–Cu, PtSi–TiW–Ni–Cu–Ni–Au). High-power 2.5kV/150A P-i-N diode with both lapped and etched anode surface was used to characterize the performance of the contacts in the conditions of free floating silicon in pressed package. The devices with PtSi contacts have the lowest forward voltage drop, but do not survive the operation in pressed package under thermal cycling. The copper based contacts with PtSi layer give lower voltage drop and better thermo-mechanical ruggedness compared to that of aluminum. These features are conserved even with passivation against corrosion using Ni–Au. The contacts without the PtSi layer have high voltage drop and fail under thermal cycling. The composition of the contact layer is shown to influence the thermal behavior of device voltage drop. The crossing point current is found to decrease with increasing contact layer thickness. The lowest magnitude gives the aluminum contact.

The grain boundary excess free volume (BFV) along with the surface tension determines the major thermodynamic properties of grain boundaries. The BFV controls to a large extent the evolution and stability of polycrystals. Unfortunately, our knowledge about the BFV is completely restricted to data generated by computer simulations, which, in turn, are strictly limited to grain boundaries in the vicinity of special misorientations. We developed a special technique that makes it possible to measure the BFV for practically any grain boundary and provides a way of estimating the BFV for grain boundaries of different classes with high accuracy. A knowledge of the BFV is especially important for fine grained and nanocrystalline systems where it opens new possibilities to design the physical properties and microstructure of such polycrystals.

A new method is introduced to determine the absolute value of the boundary excess free volume. Along with the boundary energy the excess free volume belongs to the major thermodynamic properties of grain boundaries. The method utilizes the dependence of the contact angle at triple junctions of grain boundaries in Al-tricrystals on hydrostatic pressure. We investigated <111> tilt boundaries in the pressure range up to 14 kbar. In particular, for a 40° <111> tilt boundary with 2° twist component the boundary free volume was found to be equal to 5.03×10-11 m3/m2.

We report on the lattice location of ion-implanted Ca and Sr in thin films of single-crystalline wurtzite GaN. Using the emission channeling technique the angular distributions of β− particles emitted by the radioactive isotopes 45Ca (t1/2=163.8 d) and 89Sr (t1/2=50.53 d) were monitored with a position-sensitive detector following 60 keV room-temperature implantation. Our experiments give direct evidence that ∼90% of Ca and >60% of Sr atoms were occupying substitutional Ga sites with root mean square displacements of the order of 0.15–0.30 Å, i.e., larger than the expected thermal vibration amplitude of 0.074 Å. Annealing the Ca implanted samples at 1100–1350 °C in high-pressure N2 atmosphere resulted in a better incorporation into the substitutional Ga site. The Sr implanted sample showed a small decrease in rms displacements for vacuum annealing up to 900 °C, while the substitutional fraction remained nearly constant. The annealing behavior of the rms displacements can explain why annealing temperatures above 1100 °C are needed to achieve electrical and optical activations, despite the fact that the majority of the acceptors are already located on Ga sites immediately after ion implantation.

Reliability of high-power silicon diodes with different anode contact material (Al, PtSiCu, PtSiCuAu) was tested in the conditions of free-floating silicon in pressed package. Pressure, thermal and cycling tests were applied without foils to buffer excessive loading. Thin PtSi layer was found too brittle for usage in so hard conditions. Copper stacks with thin PtSi interlayer provide low voltage drop and show potential to survive such hard stress conditions under thermal and power load cycle. 5 μm thick PtSiCu contacts showed the best thermo-mechanical properties.

Aluminum (AI, PtSi-AI, PtSi-TiW-AICuSi) and copper (TiW-Ni-Cu, PtSi-TiW-NiCu) based contact stacks for high-power devices are compared using the measured forward I-V curves of P-i-N diodes. PtSi layer on silicon surface is found necessary to obtain low overall contact resistance and voltage drop of the device in the ON-state. The diodes with top layer from copper show lower overall contact resistance and better mechanical stability compared to that of aluminum

The pressure effect on the rate of the Discontinuous Ordering reaction in the Fe - 50% at. Co system was studied. The distribution function for the activation volume for the grain boundary self-diffusion as a function of grain boundary structure was determined. The activation volumes range from 0.15 to 0.38 in atomic volume units. The result was interpreted in terms of a vacancy mechanism of GB diffusion with a varying degree of vacancy relaxation depending on the grain boundary structure.

Gallium nitride, aluminum nitride and indium nitride are basic materials for blue optoelectronic devices. The essential part of the technology of these devices is annealing at high temperatures. Thermodynamic properties of the Ga–N system and their consequences to application of high nitrogen pressure for the annealing of GaN based materials are summarized. The diffusion of Zn, Mg and Au in high dislocation density heteroepitaxial GaN/Al2O3 layers will be compared with the diffusion in dislocation-free GaN single crystals and homoepitaxial layers. It will be shown that high dislocation density can drastically change the diffusion rates, which strongly affects the performance of nitride devices. Inter-diffusion of Al, Ga and In in AlGaN/GaN and InGaN/GaN quantum well (QW) structures will be also considered. It will be shown that in contrast to stability of metal contacts, which is strongly influenced by dislocations, the inter-diffusion of group III atoms in QW structures is not affected strongly by the presence of high dislocation density. This is related to the different rate controlling slow process in these two diffusion processes. This feature of interdiffusion processes explains the success of heteroepitaxial techniques in the technology of nitride based light emitting diodes.

The kinetics of lateral spreading of Cd18Cu6 intermetallics along a free Cu surface from Cd source was studied under hydrostatic pressures 0.05 and 0.9 GPa in the temperature range 200 - 280 degreesC by SEM, AFM and optical microscopy methods, Arrhenius equations for Cd diffusion coefficients over Cd18Cu6 surface in dependence on pressure were obtained and surface diffusion activation volumes determined. Adatom surface diffusion mechanism with "traps" at the elementary steps is discussed.

Defect recovery, optical activation and diffusion of Er implanted GaN epilayers grown on sapphire were studied after annealing at 1000°C with proximity cap and 1200°C under nitrogen atmosphere at high pressure (1GPa). The erbium ions with 160 keV were implanted at room temperature to nominal fluences of 5×1014 cm−2 and 5×1015 cm−2. Some samples were co-implanted with oxygen ions to study its influence on the Er behaviour. During implantation a large fraction of Er is incorporated in Ga sites of the GaN lattice for the samples implanted with lower dose. The implantation damage recovers almost completely after rapid thermal annealing (120 s) at 1000°C with proximity cap. The annealing has no influence on the Er profile. The increase of the annealing time leads to the degradation of the surface due to nitrogen loss. The samples implanted with higher fluence and exposed to the same annealing procedure display distinct behaviour depending on the presence of oxygen. In samples without oxygen, the recovery is faster and accompanied by the segregation of Er towards the surface. For samples containing oxygen the damage recovery proceeds slowly and the Er profile remains stable. Annealing at 1200°C in nitrogen atmosphere at a pressure of 1GPa promotes the complete recovery of the damage in the sample without oxygen. During this annealing, a fraction of Er diffuses into the bulk. After annealing the optical spectra reveal the presence of several sharp lines the intensity of which increases significantly with the annihilation of the implantation damage.

Transmission electron microscopy was used to study the defects generated in GaN heteroepitaxial layers during diffusion of Au, Zn and Mg in the temperature range 900 degreesC - 1200 degreesC. The diffusion annealings were carried out under N-2 pressure of 1 GPa in order to avoid decomposition of GaN. Diffusion of the metals into the GaN layers was connected with formation of voids and nanotubes along dislocation cores. The penetration profiles were measured by means of SIMS. The effective diffusion coefficients and the activation energy for Au diffusion in GaN were calculated.

The effect of pressure and temperature on the distribution function for the activation energy and activation volume of the discontinuous precipitation reaction in a Cu - 7.5 at.% In alloy has been studied. For each pressure and temperature the distribution functions for the activation energy and activation volume for the grain boundary (GB) diffusivity were determined. It was found that the average activation volume increases from 0.75 to 1.5 atomic volumes, when the temperature is increased from 310 to 370°C. At each temperature the activation energy and activation volume vary within 15% to 30% around the average.

Evolution of concentration profiles during interdiffusion in three-layer samples Cu(5 at.% Sn)-Ni(5 at.% Sn)-Cu(5 at.% Sn) with inert markers has been studied by the methods of optical microscopy and SEM with X-ray microprobe analysis. 'Up-hill' diffusion of Sn and formation of two-phase zones with periodically changing precipitates of (NiCu)(3)Sn and metastable solution have been found. Interrelation between Kirkendall and Frenkel effects and 'up-hill' Sn diffusion has been discussed.