Properties of SiO₂-GaAs and Au-Ti-SiO₂-GaAs structures used in production of transmission lines

We investigated electrophysical properties of the SiO₂-GaAs and Au-Ti-SiO₂-GaAs structures that are used in technological process when manufacturing transmission lines for microwave integrated circuits. The SiO₂-GaAs structures were formed using different techniques, namely, (i) monosilane oxidation in oxygen, (ii) high-temperature tetraethoxysilane decomposition, (iii) high-frequency cathode sputtering of quartz in argon plasma, and (iv) electron-beam evaporation of quartz in a vacuum. The SiO₂ films obtained using monosilane oxidation or electron-beam evaporation of quartz demonstrated better properties. For the Au-Ti-SiO₂-GaAs structures a layer structure transformation was shown to occur, with formation of TiOx-SiO₂ junction and gold atoms penetration over the whole adhesion layer thickness. The microwave oscillator modules made using the Au-Ti-SiO₂-GaAs (Si) structures demonstrated output power of 10-60 mW in the 8 mm wavelength range

Interface features of SiO₂/SiC heterostructures according to methods for producing the SiO₂ thin films

In this work, we studied comparative characteristics of the SiO₂/SiC heterostructures. The following two techniques were used for SiO₂ formation: thermal oxidation in water vapor (i) and oxidation in solution (ii). According to experimental results obtained from optical absorption and photoluminescence spectra as well as from measurements of internal mechanical stresses, one can conclude that the thin SiO₂ films prepared using the technique (ii) possess SiO₂/SiC interface with a less number of defective states than that for SiO₂ films prepared using the technique (i)

Temperature dependence of contact resistance of Au−Ti−Pd2Si−n⁺ -Si ohmic contacts

We investigated temperature dependence of contact resistance of an Au−Ti−Pd₂Si ohmic contact to heavily doped n⁺ -Si. The contact resistance increases with temperature owing to conduction through the metal shunts. In this case, the limiting process is diffusion input of electrons to the metal shunts. The proposed mechanism of contact resistance formation seems to realize also in the case of wide-gap semiconductors with high concentration of surface states and dislocation density in the contact

Some aspects of thermal resistance measurement technique for IMPATT and light-emitting diodes

Some aspects of measuring the thermal resistance to a constant heat flow at a p-n junction–package region in IMPATT and light-emitting diodes are considered. We propose a method of studying the thermal resistance of high-power light-emitting diodes. This method makes it possible to increase accuracy of measuring the thermal resistance by determining the temperature at a linear section of the voltage−temperature curve. A possibility to measure the thermal resistance of IMPATT diodes by using the pulse I-V curves is shown. This enables one to simplify calculations and increase accuracy of measuring the thermal resistance

Ohmic contacts to Hall sensors based on n-InSb-GaAs(i) heterostructures

We consider ohmic contacts to the n-InSb epitaxial layers grown on a semi-insulating GaAs substrate. The ohmic contacts are formed through titanium metallization with subsequent gilding. Using the structural (AFM and XRD) and analytical (AES) techniques, we showed that thermal annealings at Т = 300 °С (for 60 s) and 360 °С (for 30 s) do not change the phase composition of the metallization. This ensures thermal stability of the contacts and Hall sensors made on the basis of Au–Ti–n-InSb–GaAs(i) structures

A silicon carbide thermistor

We consider a silicon carbide thermistor with multilayer Au–TiBx–Ni2Si ohmic contacts intended for operation in the 77 to 450 K temperature range

Effect of microwave radiation on I-V curves and contact resistivity of ohmic contacts to n-GaN and n-AlN

We studied ohmic contacts Au-Pd-Ti-Pd-n-AlN and Au-TiB₂-Al-Ti-n-GaN with contact resistivity ρс = 0.18cm² and 1.6 *10⁻⁴ Ω∙cm² , respectively, and the effect of microwave treatment on their electrophysical properties. After microwave treatment for time t up to 1000 s, the contact resistivity dropped by 16% (60%) in the contact to AlN (GaN). This seems to result from increase of the number of structural defects in the semiconductor near-contact region caused by relaxation of intrinsic stresses induced by microwave radiation

Heat-resistant barrier and ohmic contacts based on TiBx and ZrBx interstitial phases to microwave diode structures

We investigated thermal stability of Au–TiBx (ZrBx) barrier contacts, as well as ohmic contacts with a TiBx diffusion barrier to n-Si (GaAs, InP, GaP, GaN, SiC). The electrophysical measurements of Schottky barrier diodes and ohmic contacts were performed both before and after rapid thermal annealing (RTA) up to 600 °С for the structures on Si, GaAs, InP and GaP, as well as up to higher temperatures for GaN (~900 °C) and SiC (~1000 °C). The concentration depth profiles of contact components were taken using Auger electron spectrometry, while phase composition and surface morphology of the metallization layers on test structures were determined using x-ray diffraction and atomic force microscopy. It was shown that the silicon, indium phosphide, gallium phosphide and gallium arsenide contact structures retained their properties and layer structure after RTA up to 600 °С. Contact degradation occurred at a temperature of 800 °С. The structures based on SiC (GaN) remained stable at temperatures up to 1000 °С (900 °С)

Effect of rapid thermal annealing on properties of contacts Au-Mo-TiBx-GaAs

The analytical, structural and electrophysical techniques have been applied to studies of the thermal degradation mechanism appearing in diode structures with the Schottky barrier Au-Mo-TiBxGaAs. It was shown that the rapid thermal annealing at T = 600 °C during 60 sec in hydrogen atmosphere results in creating the ELS type center in the space charge region of GaAs. This center is represented by the complex VGa+VAs, which has been confirmed by photoluminescence measurements. It causes the appearance of excess current at the initial part of current-voltage characteristic

Theoretical and experimental modelling the specific resistance of vertical ohmic contacts Au–Ti–Pd–n⁺-n-n⁺-Si in IMPATT diodes

The method of electrophysical diagnostic of n⁺-n-n⁺ structures at the etching stage of manufacturing process of power IMPATT diodes has been proposed. A numerical method for specific contacts resistance calculation of vertical ohmic contacts with a non-uniform doping level has been developed. Vertical ohmic contacts Au–Ti–Pd–n⁺-n-n⁺-Si both before and after etching were used for experimental checking this model. It has been computed the value of contact resistance in the interface metal–n⁺ with correction of contribution of n⁺-n and n-n⁺ resistances to the total resistance. The values of total effective resistances of vertical ohmic contacts Au–Ti–Pd–n⁺-n-n⁺-Si may be calculated using the Cox–Strack method. We used solutions of Laplace’s equation for computation of specific contact resistance metal–n⁺ without contribution of interfaces n⁺-n and n-n⁺. The values of specific contact resistance were ~10⁻⁶ Ohm·cm². This method allows to control the manufacture process by monitoring the changes in electrophysical properties of the structure between etching cycles