Formation of ohmic contacts to n(p)-gan and measurement of their contact resistivity

We propose multilayer ohmic contacts to n- and p-GaN layers, with titanium boride as diffusion barrier. It is shown that the optimal method of contact resistivity measurement is the transmission line method (TLM) with circular contact geometry. The Ti−Al−TiBx−Au contact metallization to n-GaN retains its layer structure after thermal annealing at temperatures up to 900 °C. The contact resistivity ρс is (6.69±1.67)×10⁻⁵ Ω⋅cm². For the Au−TiBx−Ni−p-GaN contact structure, the contact resistivity is (1±0.15)×10⁻³ Ω⋅cm²

Дослідження впливу режимів електронно-променевої безтигельної зонної плавки металургійного кремнію на рафінування та структуроутворення зливків

The paper presents the results of studies obtained with the development of the technology of electron-beam crucible impregnation of metallurgical silicon. It is shown that refining of silicon from background and dopant impurities in electron-beam crucible-free zone melting occurs by zone purification during melting and as a result of evaporation of impurities from the sample surface.  The mathematical model and computational experiment were been performed to determine the temperature gradient at different rates of zone melting. It was found the diapason of temperature gradients, which provides the columnar structure of crystallites and the purification of the samplesdue the melting with the zone recrystallization procedure. The level of the resistivity of the ingots increases at the end.У роботі представлені результати досліджень, які отримані при розробці технології електронно-променевої безтигельної зонної плавки металургійного кремнію. Показано, що рафінування кремнію від фонових і легуючих домішок при електронно-променевій безтигельній зонній плавці відбувається шляхом зонного очищення при плавці і в результаті випаровування домішок з поверхні зразка. Створено математичну модель і проведено обчислювальний експеримент, за допомогою якого визначено температурний градієнт при різних швидкостях зонного плавлення. Встановлено межі температурних градієнтів, при яких в процесі плавки формується стовпчаста структура кристалітів, що забезпечує разом з очищенням зразків в результаті зонної перекристалізації підвищення рівня питомого електроопору зливків

Novel technological possibilities for growth of GaAs autoepitaxial films, and properties of Gunn diodes made on their basis

The n⁺-n-n⁺-n⁺⁺-GaAs epitaxial structures were MBE-grown on porous nanostructured and traditional (standard) heavily doped n⁺⁺-GaAs substrates. On their basis, we fabricated the Gunn diodes generating power output in the 44−59 GHz (first harmonic) and 101−104 GHz (second harmonic) frequency ranges. For both harmonics, the power output of the Gunn diodes grown on porous substrates was shown to be from 20 to 30 % higher than those grown on the flat ones

Baikal-GVD

We present the status of the Gigaton Volume Detector in Lake Baikal (Baikal-GVD) designed for the detection of high energy neutrinos of astrophysical origin. The telescope consists of functionally independent clusters, sub-arrays of optical modules (OMs), which are connected to shore by individual electro-optical cables. During 2015 the GVD demonstration cluster, comprising 192 OMs, has been successfully operated in Lake Baikal. In 2016 this array was upgraded to baseline configuration of GVD cluster with 288 OMs arranged on eight vertical strings. Thus the instrumented water volume has been increased up to about 5.9 Mtons. The array was commissioned in early April 2016 and takes data since then. We describe the configuration and design of the 2016 array. Preliminary results obtained with data recorded in 2015 are also discussed

Baikal-GVD: Results, status and plans

The future next-generation neutrino telescope Baikal-GVD will be a km3-scale array aimed at the detection of astrophysical neutrino fluxes. It will have modular structure and consist of functionally independent sub-arrays – clusters of strings of optical modules. The prototyping phase of the project has been concluded in 2015 with the deployment of the first cluster of Baikal-GVD in Lake Baikal. We discuss the current status and perspectives of the Baikal-GVD project

The optical module of Baikal-GVD

The Baikal-GVD neutrino telescope in Lake Baikal is intended for studying astrophysical neutrino fluxes by recording the Cherenkov radiation of the secondary muons and showers generated in neutrino interactions. The first stage of Baikal-GVD will be equipped with about 2300 optical modules. We describe the design of the optical module, the front-end electronics and the laboratory characterization and calibration before deployment

Acoustic Search for High Energy Neutrinos in Lake Baikal: Status and Perspectives

The status and perspectives of the feasibility study to detect high energy cosmic neutrinos acoustically in Lake Baikal is presented. The concept of on acoustic array as a part of the Baikal Gigaton Volume Neutrino Telescope GVD based on results of simulation and background measurements is described