The temperature stability of Ge/Au/Ni/Au ohmic contacts to GaAs nanoheterostructures and Ti/Al/Ni/Au ohmic contacts to GaN nanoheterostructures on silicon substrate was investigated. It has been established that optimization of the RTA process made it possible to obtain ohmic contacts with field emission current flow mechanism. The thermal stability of ohmic contacts for transistors and mesa resistors demonstrated the threshold behavior of the heat treatment temperature. The optimum process parameters for temperature stability and minimum contact resistance were defined. Keywords: ohmic contact, gallium arsenide, gallium nitride.

This letter reports a nitrogen ion implantation through silicon nitride passivation layer deposited on AlGaN/GaN on Si heterojunction structure. Employment of Si3N4 layer simplify HEMT fabrication process and helps to obtain high resistivity isolation due to the shift of implanted ions distribution towards the surface of semiconductor. This isolation process in combination with C-doped heterostructure buffer layer results in increased up to 650 V breakdown voltage. Keywords: ion implantation, breakdown voltage, GaN, power transistor.

The temperature stability of Ge/Au/Ni/Au ohmic contacts to GaAs nanoheterostructures and Ti/Al/Ni/Au ohmic contacts to GaN nanoheterostructures on silicon substrate was investigated. It has been established that optimization of the RTA process made it possible to obtain ohmic contacts with field emission current flow mechanism. The thermal stability of ohmic contacts for transistors and mesa resistors demonstrated the threshold behavior of the heat treatment temperature. The optimum process parameters for temperature stability and minimum contact resistance were defined.

This letter reports a nitrogen ion implantation through silicon nitride passivation layer deposited on AlGaN/GaN on Si heterojunction structure. Employment of Si3N4 layer simplify HEMT fabrication process and helps to obtain high resistivity isolation due to the shift of implanted ions distribution towards the surface of semiconductor. This isolation process in combination with C-doped heterostructure buffer layer results in increased up to 650 V breakdown voltage.

The effect of atomic composition on the rate of plasma chemical etching of silicon nitride in power transistors based on an AlGaN / GaN heterojunction is studied. It is shown how the subsequent process of its plasma-chemical etching depends on the configuration of the incorporation of hydrogen impurity atoms into the molecular structure of the silicon nitride deposited in the plasma. The dependence of the etching rate on the parameters of the process (the working pressure in the chamber, the power of the plasma generator, the flow of working gases, the deposition temperature) is investigated. It was shown that the etching rate of the HxSirNzHy film does not depend directly on the hydrogen content, but significantly depends on the ratio of [Si-H] / [N-H] bonds. The etching rate of HxSirNzHy in a high-density plasma at low powers is much less dependent on the configuration of hydrogen bonds than the etching rate of this dielectric in a buffer etchant.

The effect of atomic composition on the rate of the plasma-chemical etching of silicon nitride in high-power transistors based on an AlGaN/GaN heterojunction is studied. It is shown how the subsequent process of its plasma-chemical etching depends on the configuration of the incorporation of hydrogen impurity atoms into the molecular structure of silicon nitride deposited in the plasma. The dependence of the etching rate on the process parameters (the working pressure in the chamber, the plasma-generator power, the working-gas flows, and the deposition temperature) is investigated. It is shown that the etching rate of the HxSirNzHy film is independent directly on the hydrogen content but significantly depends on the ratio of [Si–H]/[N–H] bonds. The etching rate of HxSirNzHy in high-density plasma at low powers is much less dependent on the configuration of hydrogen bonds than the etching rate of this dielectric in a buffer etchant.

The process of ion implantation into silicon carbide is studied in this paper. We conducted an analysis of acceptor distribution profiles. We determined that silicon carbide layers with an orientation (11–20) have a higher degree of crystal lattice recovery after ion implantation with aluminum ions than a crystal lattice with an orientation (0001). A significantly higher efficiency of ion doping of silicon carbide with an orientation (11–20) was shown, which may indicate a more efficient recrystallization of the fastest growing crystallographic direction. We have established a higher degree of restoration of the crystal lattice of silicon carbide implants with an orientation (11–20) after implantation. Highly doped SiC p-layers were obtained with a specific resistance of about 0.02 Ohm*cm and with high crystalline structure quality without the use of ultra-large implantation doses. The minimum value of Rs for orientation (0001) is about 10 k Ω/□, and for orientation (11-20) - 2.7 k Ω/□.

For silicon carbide, the problem of obtaining low-resistance ohmic contacts with improved service characteristics remains topical despite a significant body of experimental data. The influence exerted by the composition of Ni and TiAl metallization, alloying parameters, additional doping of the contact layer of silicon carbide (SiC) with N+ nitrogen ions, and the crystallographic Si- or C-face on the resistance of ohmic contacts  to n-6H-SiC  is examined.  It is  found  that the greatest influence on how ohmic contacts to n-6H-SiC are formed is exerted by the alloying process resulting in a decrease in the contact resistance by approximately six times. The process of additional doping with N+ also reduces the contact resistance by nearly a factor of four. It is found that low-resistance contacts can be obtained on both faces with approximately the same low resistance. TiAl metallization is optimal for the C-face, and Ni metallization, for the Si-face. This choice of metallization makes it possible to obtain ohmic contacts on both polar faces with approximately the same resistances on the order of 2.5 × 10–4 Ω cm2.

The preparation of ohmic contacts to heterobipolar nanostructures has a number of characteristic features. In addition to the basic requirement of minimizing contact resistance, contacts to this type of structures have a transition layer whose depth of penetration must not exceed the emitter layer’s thickness, due to the possibility of short-circuiting the emitter base p – n junction. In this work, the effect the main technological parameters of rapid thermal annealing have on a contact’s characteristics are examined, and the process of obtaining a low-resistance ohmic contact to heterobipolar transistor layers is optimized. Ohmic contacts to the n -layers of heterobipolar nanoheterostructures based on gallium arsenide and produced via layer-by-layer electron-beam deposition of Ge/Au/Ni/Au are considered. The diffusion distribution profiles of doping with Ge impurities are calculated as a function of the time and temperature of rapid thermal annealing, and are examined via scanning electron microscopy. It is found that rapid thermal annealing for 60 s at a temperature of 398°C yields ohmic contacts with low resistance, smooth surface morphology, and the minimum size of the transition layer.

The conditions for the growth of epitaxial layers are considered and the resistance of alloyed ohmic contacts to tellurium-doped gallium arsenide layers is studied. The use of the (AuGe eutectic alloy)-Ni–Au composition alloy of ohmic contacts to the gallium arsenide layers with electron conductivity, including use as a contact layer of a narrow-band (In0.5Ga0.5As), makes it possible to achieve a resistance of 10–7 Ohm cm2, in the best case; however, this leads to a deterioration of the surface morphology. In this paper, we study the issues of doping the GaAs contact layer by tellurium to the maximum concentration of 2.5 × 1019 cm–3. In this case, the resistance of the ohmic contacts proves to be less than 5 × 10–8 Оhm cm2, simultaneously with the improvement of the semiconductor’s surface morphology.

In this paper, the electrical properties of TiAl- and Ni-based ohmic contacts formed on n-type 4H- and 6H-SiC were studied. The dependence of the contact resistance on technological process was investigated. Ohmic contacts were formed by electron-beam deposition to different surfaces of silicon carbide. Short-term plasma-chemical etching of the active layer was used to improve TiAl-based contact to C-surface 4H-SiC. Using of Ni-based contacts to the Si-surface and TiAl-based to C-surface makes it possible to obtain a resistance of about 10−4 Ohm*cm2. We got the process of making good ohmic contacts to 4H- and 6H-silicon carbide.

This paper investigates ohmic contacts to n-GaAs layers of the heterobipolar nanoheterostructures obtained through electron-beam evaporation of Ge, Au, Ni, and Au layer-by-layer. The effect of the firing time and temperature on the contact resistance is considered. Based on the analysis of the characteristics of the ohmic contacts, a firing installation of a special design and a firing technique are developed. The technique ensures the minimum contact resistance for the minimum size of a transition layer, satisfactory morphology, and even edges of the contacts.

Ohmic contacts to n-layers of gallium arsenide-based heterobipolar nanoheterostructures obtained by layer electron-beam evaporation Ge/Au/Ni/Au are studied. Time and temperature dependencies of diffusion profiles of doping Ge distribution are calculated. The interface of metal-semiconductor is analyzed with SEM, then an RTA installation design and methodology of RTA are suggested based on the results of this study. This allows to obtain ohmic contacts with low resistance and minimum transition layer.

Dependence of the chemical composition of a film of plasma-chemical silicon nitride on the technological parameters of the deposition process is studied. The stages in which the process parameters are optimized in order to improve the masking properties of the film are described. A systematic study of the Fourier-transform infra-red (IR) spectra of plasma-chemical silicon-nitride films is carried out. It is found that the chemical resistance of a silicon-nitride film depends on the configuration in which hydrogen is incorporated into chemical bonds.