Ksenia Shubina

Due to a large number of applications in the near and short-wave IR spectrum and a relatively high detectivity, PIN photodiodes based on epitaxial InGa(Al)As/InP heterostructures are of a great scientific interest. The operational spectral range of such photodetectors is up to 2.6 μm. However, to reach such wavelengths it is necessary to synthesize heterostructures with metamorphic buffer layers. In our study, we investigated the current-voltage and capacitance–voltage characteristics of PIN photodiodes based on InGa(Al)As/InP heterostructures with an original metamorphic buffer layer and an In0.83Ga0.17Asabsorbing layer grown by means of molecular beam epitaxy. The photodiode chips were formed using standard post-growth processing techniques. The diameter of the photosensitive area of the obtained diodes was 140 μm. The dark currents and the shunt resistance were ~ 300 nA and ~ 25 kΩ at the voltage of -10 mV respectively. Therefore, the suggested metamorphic buffer layer effectively eliminates threading dislocations in the active area of the heterostructure. The obtained heterostructures with metamorphic buffer layers can be used to produce IR photodetectors for the spectral range of 2.2-2.6 μm

Nickel oxide is a promising material for transparent electronics applications. This semiconductor demonstrates the possibility of modifying its physical properties depending on the method of growth and subsequent processing. Here the effects of the discharge power are reported during reactive dc magnetron sputtering, as well as the modes of subsequent annealing of NiO films, on their structural, electrical, and optical properties. NiO films are annealed at various temperatures both in an oxygen‐containing environment and under vacuum conditions. Deposited NiO films have a polycrystalline structure with a preferred orientation (200) for the low discharge power mode and (111) for the high discharge power mode. However, obtained NiO films exhibit crystallinity improvement after annealing. The presence of both Ni²⁺ and Ni³⁺ oxidation states in the deposited films is found. In addition, it is shown that the relative carrier concentration (Ni³⁺/Ni²⁺ peak area ratio) can be controlled by choosing the NiO film preparation mode. The trend in this ratio corresponds to the trend in film conductivity and the number of free‐charge carriers. The deposited films are semitransparent, and the estimated optical bandgap of NiO is in the range from 3.50 to 3.74 eV.

Fabrication of electric contacts is one of the most important stages in the electronic devices manufacturing process. Recently, considerable attention is paid to non-alloyed ohmic contact studies, although the more conventional approach usually involves contact formation by rapid thermal annealing of the sputtered metallization. In this work the contact resistance of alloyed (Ti/Al/Ni/Au and Ti/Al) and non-alloyed (Yb/Au) ohmic contacts to n-GaN epitaxial films is compared. Ti/Al/Ni/Au alloyed ohmic contacts have the lowest resistance. However, it is found that the contact resistance values for non-alloyed Yb/Au and alloyed Ti/Al contacts are similar. Thus, low-resistance non-alloyed Yb/Au-based ohmic contacts to n-GaN are demonstrated.

This paper investigates the optical and electrical properties of ITO films for their application as a transparent contact electrode to NiO films. The films were fabricated by magnetron sputtering at various parameters of the discharge power and oxygen content in the working gas mixture. Structural analysis showed an increase in the crystallinity of the films during their subsequent annealing. The films demonstrate high conductivity and transparency with an absorption edge higher than that of NiO films. The results of the study show a high potential for using ITO films to create a transparent electrode to NiO layers.