Radiation effects and interphase interactions in ohmic and barrier contacts to indium phosphide as induced by rapid thermal annealing and irradiation with γ-ray 60Co photons

The radiation resistance of Au-Pd-Ti-Pd-n ⁺⁺-InP ohmic contacts and Au-TiB _x -n-n ⁺-n ⁺⁺-InP barrier contacts—both initial and subjected to a rapid thermal annealing and irradiated with ⁶⁰Co γ-ray photons with doses as high as 10⁹ R—has been studied. Before and after external effects, the electrical characteristics of the barrier and ohmic contacts, distribution profiles for components, and phase composition in the metallization layers have been measured. In ohmic Pd-Ti-Pd-Au contacts subjected to rapid thermal annealing and irradiation, a significant distortion of the layered structure of metallization occurs; this distortion is caused by the thermal and irradiation-stimulated transport of Pd over the grain boundaries in polycrystalline Ti and Au films. However, the specific contact resistance ρ _c does not change appreciably, which is related to a comparatively unvaried composition of the contact-forming layer at the Pd-n ⁺-InP interface. In the initial sample and the sample subjected to the rapid thermal annealing at T = 400°C with the Au-TiB _x -n-n ⁺-n ⁺⁺-InP barrier contacts and irradiated with the dose as high as 2 × 10⁸ R, a layered structure of metallization is retained. After irradiation with the dose as high as 10⁹ R, in the samples subjected to a rapid thermal annealing at T = 400°C, the layered structure of metallization becomes completely distorted; however, this structure is retained in the initial sample. The electrical properties of the contact structure appreciably degrade only after irradiation of the sample preliminarily subjected to a rapid thermal annealing at T = 400°C.     

Effect of p-n junction overheating on degradation of silicon high-power pulsed IMPATT diodes

The thermal limits of the two-drift impact avalanche and transit-time (IMPATT) diode operating in the pulsed mode in the 8-mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p-n junction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C relative to an ambient medium. The temperature limit of junction overheating, above which IMPATT diodes rapidly degrade, was determined as 350°C. The presented results of X-ray phase analysis and depth profiles of Au-Pt-Ti-Pd-Si ohmic contact components confirm thermal limits of the IMPATT diode operating in the pulsed mode.

     

Thermal stability of graphite-Cobalt nanocomposite materials

Graphite-Co composites produced by intercalating potassium into graphite to give C₈K, followed by reaction with CoCl₂ and reduction of Co were characterized by x-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, and secondary ion mass spectrometry. The results indicate that the Co in the composites is present both between graphite layers, in the form of atomically dispersed metal (intercalated into graphite), and on the surface of the graphite support, in the form of nanoparticles. Heat treatment of the nanocomposites in several steps increases the amount of cobalt on the graphite surface relative to that between the graphite layers owing to the outdiffusion of cobalt atoms from the interlayer spaces. Heating markedly increases the magnetic susceptibility of the graphite-Co composites, also by virtue of the Co diffusion to the surface of the graphite particles and the formation of Co agglomerates.     

Solidus Surface of the Mo–Fe–B System

Powder Metallurgy and Metal Ceramics - The arc-melted Mo–Fe–B alloys with boron content up to ~41 at.% were studied after annealing at subsolidus temperatures by X-ray diffraction,...     

Mechanism of current flow in a Au-Ti-Al-Ti-n +-GaN ohmic contact in the temperature range of 4.2–300 K

The temperature dependence of the contact resistivity ρ _c (T) of Au-Ti-Al-Ti-n ⁺-GaN ohmic contacts is studied experimentally and substantiated theoretically in the temperature range T = 4.2–300 K. It is shown that the saturation portion of ρ _c (T) is observed in the low-temperature measurement region (4.2–50 K). As the temperature increases, ρ _c decreases by the exponential law. The experimental and calculated dependences ρ _c (T) are in agreement. The obtained results make it possible to conclude the field nature of the current transfer for the saturation region of ρ _c (T) and the thermal-field one, for the exponential region.     

Thermal-resistant TiB x -n-GaP Schottky diodes

The effect of rapid thermal annealing on the parameters of TiB _x -n-GaP Schottky barriers and interphase interactions at the TiB _x -GaP interface are studied. It is shown that the contact TiB _x -n-GaP system features an increased thermal stability without varying the electrical parameters of the Schottky barrier at temperatures as high as 600°C.     

On the features of mechanochemical synthesis of Y-Cu equiatomic powder mixture

Structural features of nanocomposite YCu powder material obtained by mechanical alloying of the equiatomic Y-Cu elemental powder mixture in a high-energy ball mill have been characterized by X-ray diffraction, and scanning electron microscopy. It has been shown that YCu compound with a full ordered CsCl-type structure along with YCu₂ intermetallic have formed at early stage of the milling process (10?min) while a long-time processing product contains these phases as well as Y₂O₃ oxide. The nanoindentation measurements of the bulk samples compacted after 60 and 120?min of milling have revealed that the mean hardness values H for these samples are higher than those for conventional bulk YCu intermetallic obtained by arc melting. The main reasons for hardness increase are fine-grained microstructure and reinforcement of material by Y₂O₃ particles uniformly distributed throughout the volume.     

Interphase interactions and the mechanism of current flow in Au-TiB x -AuGe-n-GaP ohmic contacts

Au-TiB _x -AuGe-n-GaP ohmic contacts have been investigated before and after rapid thermal annealing at T = 723, 773, and 873 K for 60 s in a hydrogen atmosphere. It is shown that the contact resistivity decreases with an increase in temperature in the range 77–232 K due to the thermionic nature of current flow in inhomogeneous ohmic contacts, while in the range 232–386 K the contact resistivity increases, which can be related to the conduction through metal shunts.     

Electrical Properties of Highly Absorbing Ceramics in the AlN–SiC System

Powder Metallurgy and Metal Ceramics - The electrical properties of two highly absorbing AlN–SiC composites are compared at a frequency of 10.3 GHz. To estimate the dielectric constant and...