Materials of Electronics Engineering (E-Journal) / Известия высших учебных заведений. Материалы электронной техники
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К 100−летию СО ДНЯ РОЖДЕНИЯ ВСЕВОЛОДА ВАЛЕРЬЕВИЧА КРАПУХИНА (1915—2009 гг.)
Get PDF«Инженер от Бога! Свидетель становления всех технологий... Великолепный организатор… Человек, знающий, что и когда надо делать», — так говорили о профессоре Всеволоде Валерьевиче Крапухине его коллеги по работе, друзья.«Инженер от Бога! Свидетель становления всех технологий... Великолепный организатор… Человек, знающий, что и когда надо делать», — так говорили о профессоре Всеволоде Валерьевиче Крапухине его коллеги по работе, друзья
КОНТРОЛЬ «ЖЕЛТОЙ» ФОТОЛЮМИНЕСЦЕНЦИИ ГЕТЕРОСТРУКТУР AlGaN/GaN
Get PDFPhotoluminescence with the peak corresponding to yellow light in the visible spectrum (the so−called yellow luminescence) is generated by deep levels in the buffer GaN layer of the ehterostructures and depeonds on heterostructure growth conditions. In turn, the deep levels affect the resistivity of the ohimic contacts of RF transistors based on these heterostructures. This determines the reliability of GaN HF transistor operation. Two types of instruments have been developed for controlling photoluminescence with the peak in the yellow spectral region for characterizing the quality of AlGaN/GaN/SiC and AlGaN/GaN/Al2O3 heterostructures. One of them provides for rapid control of yellow photoluminescence and the other allows mapping of photoluminescence across the heterostructure area. Examples of photoluminescence maps for experimental structures grown on different substrates have been given.Фотолюминесценция с максимумом, соответствующим желтому цвету свечения видимого спектра (так называемая желтая люминесценция), определяется глубокими уровнями в буферном слое GaN гетерооструктур и зависит от условий роста гетероструктур. В свою очередь, глубокие уровни влияют на сопротивление омических контактов СВЧ−транзисторов, изготовленных на таких гетероструктурах. Это обуславливает надежность работы СВЧ−транзисторов на основе GaN.Разработаны два типа установок для контроля фотолюминесценции c максимумом в желтой части видимого спектра, предназначенные для характеризации качества гетероструктур AlGaN/GaN/SiC и AlGaN/GaN/Al2O3. Одна их представленных установок позволяет проводить «экспресс− контроль» желтой фотолюминесценции, а другая — снимать «карты» фотолюминесценции по площади пластин с гетероструктурами. Приведены примеры «карт» фотолюминесценции для структур, выращенных на различных подложках
ВЛИЯНИЕ КАЧЕСТВА ПОДЛОЖЕК SiC НА СТРУКТУРНОЕ НСТВО И НЕКОТОРЫЕ ЭЛЕКТРИЧЕСКИЕ ПАРАМЕТРЫ ПЛЕНОК AlGaN/GaN
No full textWe have analyzed the effect of volume and surface defects SiC substrates on structure and some electrophysical parameters of AlGaN/GaN epitaxial layer heterostructures grown on them. Regions with internal stresses usually induced by carbon rich disk−shaped inclusions were detected in the initial substrates. We show experimentally that the presence of internal stresses in SiC could affect the microroughness of epitaxial films in regions above stressed areas. Abrupt deterioration of electrophysical parameters was observed in regions of epitaxial films growing above areas with internal stresses in the substrate. AlGaN/GaN layers contain impurities delivered to their bulk during epitaxy or preparatory operations.Дан анализ влияния объемных и поверхностных дефектов подложек SiC на структуру и некоторые электрофизические параметры выращенных на них эпитаксиальных слоев AlGaN/GaN нитридных гетероструктур. В подложках из карбида кремния обнаружено наличие областей с внутренними напряжениями, источниками которых, как правило, являются пластинчатые включения, обогащенные углеродом. Экспериментально показано, что наличие внутренних напряжений в SiC может влиять на микрорельеф эпитаксиальных пленок в областях над напряженными участками. Установлено, что в областях эпитаксиальных пленок, выращенных над областями с внутренними напряжениями в объеме подложек SiC, наблюдается резкое ухудшение электрических параметров. В слоях AlGaN/GaN обнаружено наличие ряда примесей, попадающих в них в процессе эпитаксии
СТРУКТУРА, ФАЗОВЫЙ СОСТАВ И МЕХАНИЧЕСКИЕ СВОЙСТВА КРИСТАЛЛОВ ZrO2, ЧАСТИЧНО СТАБИЛИЗИРОВАННЫХ Y2O3
Get PDFThe structure of PSZ crystals has been studied as a function of the content of the stabilizing impurity (Y2O3) by X–ray diffraction, transmission electron microscopy (TEM) and atomic−force microscope (AFM). The hardness and fracture toughness have been measured by microindentation. The study has shown that PSZ crystals obtained by directional solidification of the melt consist of two tetragonal phases (t and t’) with varying degrees of tetragonality. Increasing the stabilizing impurity concentration leads to an increase in the volume fraction of the “untransformable” t’ phase. Experiments have shown that an increase in the concentration of the stabilizing impurity leads to a growth in the amount of positively charged oxygen vacancies (the F++–centers) which increase the lattice parameter and stabilize the structure. The character of the twinned structure changes depending on the concentration of the stabilizing impurity. In PSZ crystals with Y2O3 concentration from 2.8 to 3.2 mol. % twins first, second and third orders as well as large twins consist of smaller twin domains are observed. At high concentrations of stabilizing impurities (3.7—4.0 mol. %) the twin structure becomes smaller and more uniform. This suggests that twinning occurs simultaneously and is localized within small volumes. The character of the twinned structure changes depending on the concentration of the stabilizing impurity. This work shows that the quantity of hardening (fracture toughness) is proportional to the content of the transformable t phase
ПРОЦЕССЫ ВО ВРЕМЯ ОТЖИГА КОНТАКТНЫХ СИСТЕМ Ti—Al—Ni И Ti—Al—Ni—Au
Get PDFThe Ti/Al/Ni/Au metallization system which is widely used in the technology of GaN based devices has a very important disadvantage: after annealing in nitrogen atmosphere for 30 sec. at temperature 850 оС it has rough surface with 300 nm hillocks. This creates troubles for lithographic processes. The aim of this work is to investigate the mechanism that generates the roughness of this surface and ways to minimize this disadvantage. We have studied the formation of rough surface in Ti/Al/Ni and Ti/Al/Ni/Au multilayer metallization systems. The resistivity of the metallization sheet increases with an increase of annealing temperature. This can be attributed to the mutual diffusion of metals and their active interaction with the formation of intermetallic phases. X−ray analysis proved the appearance of the following basic intermetallic phases: NiTi, Al3Ti, и Ni2Al3 in the metallization systems. After annealing the surface of metallization system Ti/Al/Ni becomes rougher; however, large hemispherical convexes (as in the Ti/Al/Ni/ Au metallization system) are not generated. Thus, the hypothesis of balling−up of molten Al−Ni alloy on the surface of metallization system Ti/Al/Ni has not been confirmed. To decrease the amount of Au–Al liquid phase that causes the rough surface of Ti/Al/Ni/Au metallization we reduced the thickness of the Au layer to 50 nm. At this Au layer thickness the surface morphology of metallization became much better: roughness reduced from 300 nm to 80 nm and the surface became specular.
ТЕОРЕТИЧЕСКОЕ ИССЛЕДОВАНИЕ ЭЛЕКТРОННЫХ И ГЕОМЕТРИЧЕСКИХ ХАРАКТЕРИСТИК ТОНКИХ ПЛЕНОК AlN
Get PDFStudy of the electronic and structural properties of AlN thin films is an important problem because these films are widely used as buffer layers for GaN−based semiconductor heterostructures growth on Si substrates. In this paper we performed a theoretical investigation of the properties of Al−terminated AlN(0001) surface in the framework of density functional theory. Ab initio calculations allowed us to study the impact of in−plane lattice strain on the surface energy of this surface. We show that the presence of the compressive strain leads to a decrease of the AlN(0001) surface energy while tensile strain increases the surface energy of this surface. Surface energy values allowed us to calculate the stress value of the surface under investigation. Also we calculated the curvature of the AlN surface as a function of film thickness for free growth. The resultant curvature values are in a good agreement with known experimental results.
ИЗУЧЕНИЕ ДЕГРАДАЦИИ ФОТОЭЛЕКТРИЧЕСКИХ ПРЕОБРАЗОВАТЕЛЕЙ НА ОСНОВЕ НАНОГЕТЕРОСТРУКТУР АIIIВV В УСЛОВИЯХ ИОНИЗИРУЮЩЕГО ИЗЛУЧЕНИЯ
Get PDFSolar radiation is practically inexhaustible and environmentally friendly source of energy. Solar panels are classified as devices very sensitive to radiation. Therefore, the problem of creating radiation− resistant solar panels is quite acute. In operation, solar batteries (SB) are exposed to hard corpuscular radiation (radiation belts, solar and cosmic radiation), resulting in the structure of accumulated violations leading to a gradual deterioration of their electrical characteristics. Conducted experimental studies of single−degradation characteristics of solar cells (SE) based on GaAs with Ge substrate due to the structural damage produced by irradiation with fast neutrons and electrons, step by irradiation with fast neutrons and electrons with different fluence. Before and after each set of neutron fluence and electrons were measured light current−voltage characteristics (CVC) and photosensitivity spectra of the AOC. Determined from the measured CVC following parameters: fault current circuit voltage with a maximum coefficient of performance (COP) (ratio of maximum power to the product of the flux density of solar energy and the cell area), fill factor (the ratio of maximum power to the product of the short−circuit current and voltage idling).
ИССЛЕДОВАНИЕ СТРУКТУРЫ И МОРФОЛОГИИ ПОВЕРХНОСТИ ДВУХСЛОЙНОЙ КОНТАКТНОЙ МЕТАЛЛИЗАЦИИ Ti/Al
Get PDFTi/Al/Ni/Au metallization widely used in the technology of GaN base devices have a very important imperfection: rough surface. There are different opinions about the causes of this imperfection: balling−up of molten aluminum or the appearance intermetallic melt phases in the Au–Al system. To check the effect of the former cause, we have studied the formation of rough surface after annealing of Ti/Al metallization which is used as a basis of many metallization systems for GaN. The substrates were made from silicon wafers covered with Si3N4 films (0.15 microns). On these substrates we deposited the Ti(12 nm)/Al(135 nm) metallization system. After this deposition the substrates were annealed in nitrogen for 30 s at 850 оС. The as−annealed specimens were tested for metallization sheet resistivity, appearance and surface morphology.We have shown that during annealing of the Ti/Al metallization system, mutual diffusion of metals and active interaction with the formation of intermetallic phases occur. This makes the metallization system more resistant to following anneals, oxidation and chemical etching. After annealing the surface of the Ti/Al metallization system becomes gently matted. However, large hemispherical convex areas (as in the Ti/Al/Ni/Au metallization system) do not form. Thus, the hypothesis on the balling−up of molten aluminum on the surface of the Ti/Al metallization system has not been confirmed
МОНТЕ—КАРЛО–МОДЕЛИРОВАНИЕ ПРОЦЕССА ФОРМИРОВАНИЯ НАНОКЛАСТЕРОВ КРЕМНИЯ В ДИОКСИДЕ КРЕМНИЯ
Get PDFThe process of silicon nanocluster formation during annealing of single SiO layers and multilayer SiO2—SiO—SiO2 structures or after Si deposition on silicon dioxide substrate was studied. A kinetic Monte Carlo model of silicon nanocluster formation taking into account silicon monoxide formation and dissociation was suggested. Not only temperature and annealing time but also SiO layer thickness determined the nanocluster sizes when SiO2—SiO—SiO2 structures were annealed. Simulation demonstrated that silicon monoxide forming in the Si—SiO2 system at high temperatures plays an important role in the process of nanocluster formation. Silicon monoxide also accounts for some specific features of 3D silicon islands formation during silicon deposition on silicon dioxide surface.Изучен процесс формирования нанокластеров кремния при отжиге одиночных слоев состава SiO и слоистых структур SiO2—SiO—SiO2 и осаждении кремния на поверхность диоксида кремния. Предложена кинетическая Монте—Карло−модель формирования нанокластеров кремния при высокотемпературном отжиге слоев SiOx нестехиометрического состава, учитывающая процессы образования и распада монооксида кремния. Установлено, что при отжиге слоистых структур SiO2—SiO—SiO2 на размеры нанокластеров, помимо температуры и длительности отжига, влияла и толщина слоя SiO. С помощью моделирования показано, что важную роль в процессе формирования нанокластеров играет газообразный монооксид кремния, образующийся в системе Si—SiO2 при высоких температурах. Монооксид определяет и особенности формирования 3D−островков кремния при осаждении кремния на поверхность диоксида кремния
РАСПРЕДЕЛЕНИЕ КИСЛОРОДА И ЭРБИЯ В КРЕМНИИ ПРИ ДИФФУЗИОННОМ ЛЕГИРОВАНИИ
Get PDFThe composition of diffusion silicon layers doped by rare earth erbium was investigated. The diffusion source was an erbium oxide layer on the surface of the test silicon wafer. The erbium and oxygen distribution profile in silicon was measured by SIMS. The concentration of electrically active erbium impurity in the diffusion layers on silicon was determined by measuring the surface resistance and carrier mobility during consecutive etching of layers. The erbium diffusion coefficient at 1240 °C was estimated to be 4.8 · 10−13 cm2 · s−1. A model of erbium and oxygen simultaneous diffusion was suggested. The model takes into account the association of erbium and oxygen into complexes. The results of numerical simulation and experimental data are in a good agreement for the near−surface region of the diffusion layer.Проведены исследования состава диффузионных слоев кремния, легированного редкоземельным элементом эрбием. Диффузия проведена из оксидной пленки эрбия, созданной на поверхности пластины кремния. Методом вторичной ионной массспектрометрии определены концентрационные профили эрбия и кислорода в кремнии. Профиль электрически активного эрбия определен методом измерения поверхностного сопротивления и подвижности носителей заряда при последовательном стравливании слоев. Рассчитан коэффициент диффузии эрбия при температуре 1240 оС, его значение составило 4,8 • 10−13 см2 • с−1. Предложена модель одновременной диффузии эрбия и кислорода в кремний, учитывающая процесс связывания эрбия и кислорода в комплексы. Путем сравнения результатов численного моделирования с экспериментальными данными показано их хорошее совпадение для приповерхностной области диффузионного слоя.