Epitaxial calcium fluoride (CaF2) layers with a nominal thickness up to 10 nm on the (111)-oriented Silicon (Si) are obtained. Surface topographies of the fluoride films are recorded and the current-voltage characteristics of the Au/CaF2/Si structures are studied. On a qualitative level, these structures exhibited all the features usual for metal-insulator-semiconductor systems. The current-voltage curves of the samples were reproduced by modeling considering a finite (0.1–1 nm) value of the standard thickness deviation of the dielectric CaF2 film.

AbstractThe currents flowing in metal–CaF_2– n -Si and metal–SiO_2–CaF_2– n -Si structures with the same (about 1.5 nm) fluoride thickness are compared in the reverse-bias mode. It is revealed that the current in the case of a two-layer dielectric can be notably higher within a certain voltage range. Such unexpected behavior is associated with the coexistence of both electron and hole components of the current as well as with the configuration of the SiO_2–CaF_2 barrier through which tunneling occurs. The results of measurements and explanatory simulation data are presented.

AbstractThe effect of increasing the tunnel current in a metal–calcium fluoride–silicon structure with addition of a silicon dioxide layer between fluoride and metal (which seems paradoxical at first glance) has been considered. This effect of nonmonotonic change in the tunnel conductivity with an increase in the insulator thickness may occur at a relatively high bias at the structure and is related to the tunnel-barrier deformation, at which electrons are tunneling through its part formed by the oxide. At low biases, the occurrence/ thickening of an additional layer leads to a natural decrease in the current. Similar behavior is possible in principle for some other combinations of materials.

AbstractA detailed simulation of degradation (caused by hot charge carriers) based on self-consistent consideration of the transport of charge carriers and the generation of defects at the SiO_2/Si interface is carried out for the first time. The model is tested using degradation data obtained with decananometer n -type-channel field-effect transistors. It is shown that the mutual influence of the above aspects is significant and their independent simulation gives rise to considerable quantitative errors. In calculations of the energy distribution for charge carriers, the actual band structure of silicon and such mechanisms as impact ionization, scattering at an ionized impurity, and also electron–phonon and electron–electron interactions are taken into account. At the microscopic level, the generation of defects is considered as the superposition of single-particle and multiparticle mechanisms of breakage of the Si–H bond. A very important applied aspect of this study is the fact that our model makes it possible to reliably assess the operating lifetime of a transistor subjected to the effects of “hot” charge carriers.

Получена 12 марта 2018 г.Принята к печати 16 апреля 2018 г

AbstractTunneling carrier transport through a thin insulator (e.g., CaF_2) layer between a Si(111) substrate and a semiconductor gate is theoretically investigated. Along with the conservation of a large transverse wave vector of tunneling particles, the limitation imposed on the availability of states in the gate is taken into account. Due to this limitation, the tunneling currents at low insulator bias are weaker than in an analogous structure with a metal gate electrode. The same feature leads to a change in the shape of the energy distribution of tunneling electrons, both in transport between the substrate and gate conduction bands and during the Si(111) conduction band–gate valence band transfer.

AbstractFor the first time, hot-carrier degradation (HCD) is simulated in non-planar field-effect transistors with a fin-shaped channel (FinFETs). For this purpose, a physical model considering single-carrier and multiple-carrier silicon–hydrogen bond breaking processes and their superpositions is used. To calculate the bond-dissociation rate, carrier energy distribution functions are used, which are determined by solving the Boltzmann transport equation. A HCD analysis shows that degradation is localized in the channel region adjacent to the transistor drain in the top channel-wall region. Good agreement between the experimental and calculated degradation characteristics is achieved with the same model parameters which were used for HCD reproduction in planar short-channel transistors and high-power semiconductor devices.

Теоретически рассмотрены условия накопления электронов в квантовой яме резонансно-туннельной структуры металл-окисел-p+-кремний и масштаб влияния накопленного заряда на распределение напряжения. Исследованы системы с SiO2, HfO2 и TiO2 в качестве диэлектрика. Показано, что появления заряда в яме при резонансном транспорте можно ожидать для структур на подложках с концентрацией акцепторов от (5-6)·1018 до (2-3)·1019 см-3 в диапазоне толщин окисла, зависящем от этой концентрации. Так, для структур с SiO2/p+-Si(1019 cм-3) толщина окисла должна превышать ~3 нм. Плотность электронов в яме может достигать величин ~1012 cм-2 и более. Однако влияние этого заряда на электростатику структуры становится заметным только в режимах сравнительно высоких напряжений, далеких от момента активации резонансного переноса через первую подзону. DOI: 10.21883/FTP.2017.04.44337.8445

Измерены и теоретически проанализированы вольт-амперные характеристики наноструктур Al/термический или электрохимический SiO2(2-4 nm)/сильнолегированный p+-Si, функционирующих как резонансно-туннельный диод. Характеристики демонстрируют особенности в виде ступеней и пиков тока, обусловленные транспортом электронов между валентной зоной кремния и металлом через дискретные уровни квантовой ямы, создаваемой зоной проводимости p+-Si и межфазной границей SiO2/p+-Si. Рассмотрены также резонансное туннелирование через уровни поверхностных состояний и появление при определенных условиях заряда вблизи указанной границы.

The stability of tunneling-thin (2–3 nm) SiO2 films during prolonged flow of high-density currents (102–103 A/cm2) was investigated. A sharp increase in the charge which a tunneling MOS structure is capable of transmitting without degradation on switching from Fowler-Nordheim injection to direct tunneling (103 C/cm2 and 107 C/cm2, respectively) was observed. The degradation of SiO2 films was investigated using Al/SiO2/n-Si/p+-Si thyristor structures with a positive bias on the semiconductor, i.e., with reverse bias of the MOS structure. The use of these devices accounted for the uniformity of the current distribution over the area and made it possible to monitor the state of the insulator layer by measuring the device gain in the phototransistor mode.

The first observation of amplification of the photogeneration current in Au/SiO 2 / n -6H-SiC structures with a tunnel-thin insulator is reported. This effect can be used to increase the efficiency of existing UV-range 6H-SiC-based photodiodes. It also shows that bipolar SiC transistors with a MOS tunnel emitter can be produced.

The physical processes which determine the behavior of n-silicon tunnel metal-dielectric-semiconductor structures at high current densities are examined. For the first time a complete analytic model is proposed for calculating the current-voltage characteristics of metal-dielectric-semiconductor structures with a high voltage on the dielectric. A "classification" of the possible current-voltage characteristics is introduced. The effect of Auger ionization of the semiconductor by injected carriers (including when a high field exists in the semiconductor) is analyzed. Calculations are presented to illustrate the dependence of the shape of the device characteristics on the level of substrate doping. A study is made of the conditions for the appearance of and the characteristics of the "switched-on" state, in which minority carriers are lost from the inversion layer not only because of tunnelling into the metal, but also because of diffusion into the interior of the semiconductor. (C) 1996 American Institute of Physics.