Abstract—CoPt films obtained by electron beam evaporation with deposition of ten Co and Pt bilayers with a total thickness of 8 nm are experimentally investigated. The Hall effect and longitudinal magnetoresistance measurements were carried out with a temperature change from 8 to 300 K. At room temperature, using magnetic force microscopy, images of domain structures corresponding to different points of the magnetization reversal curve were obtained. The possibility of studying the Hall effect on artificially created domain structures formed by the local magnetic field of the probe of an atomic force microscope is demonstrated.

The results of experimental studies of the conductivity of AlGaAs/GaAs heterostructure with two-dimensional electron gas at temperatures of 10-300 K are presented. At low temperatures, with a decrease in the distance between the contacts to the structure from 100 to 20 µm, a resistance increase was observed. To explain this anomalous dependence, a numerical simulation of the piezoelectric effect in a semiconductor on the channel conductivity is carried out. It is shown that it is necessary to take into account the crystallographic orientation of the channel and the effect on its potential of remote piezo-charges.

The electric conductivity of the AlGaAs/GaAs heterostructure with two-dimensional electron gas has been experimentally studied in a temperature range of 10–300 K. At low temperatures, electric resistance of the structure exhibited growth when the distance between contacts decreased from 100 to 20 μm. For explaining this anomalous behavior, numerical simulation of the influence of piezoeffect in the semiconductor on the channel conductivity was carried out, which showed that it is necessary to take into account the crystallographic orientation of the channel and the influence of remote piezoelectric charges on its potential.

In the study of electron transport in low-dimensional structures, semiconductor heterostructures with a two-dimensional electron gas are often used. The conductive channel of these structures is separated from the gates by insulating regions, which can be formed in a varitey of ways. The peculiarities of such structures are the high quality of the initial plates and the need to change the topology in the research process. This makes the use of photolithography ineffective.This paper discusses the technology of forming insulating grooves using an atomic force microscope — a method of pulsed force nanolithography, which allows both working with individual samples and forming narrow and deep grooves on the semiconductor that provide good insulating characteristics. The measured transport characteristics of the nanostructures created by this method confirm the presence of quantization of the channel conductivity and the absence of a noticeable number of introduced defects.

The literature concerning the features of creating ohmic contacts for GaAs/AlGaAs heterostructures with a two-dimensional (2D) electron gas with a high level of electron mobility is analyzed. The process of annealing the contacts based on the Ni/Au/Ge system is considered. The recommended published parameters of the layers to be sprayed and the regimes of their annealing are presented, which make it possible to obtain ohmic contacts with low resistance up to temperatures lower than 4 K. Several mechanisms are considered, which can lead to the experimentally observed dependence of the characteristics of the contact on its crystallographic orientation. A method for creating contacts using Au/Ge/Pd metallization, in which the contact is formed due to the mutual diffusion and interaction of metals and a semiconductor in the solid phase at temperatures lower than 200°C, is described. This ensures a higher degree of homogeneity of the contact in the composition and a smooth metal–semiconductor interface, and it can lead to decrease of the influence of orientation effects on the electric characteristics of the contact.

Квазиодномерные полупроводниковые структуры с изменяемым продольным потенциальным рельефом созданы методом импульсной силовой нанолитографии, выполняемой с использованием атомно-силового микроскопа. Структуры изготавливались на основе гетероструктур AlGaAs/GaAs с глубоким (130 нм от поверхности) залеганием двумерного электронного газа. Потенциальный профиль канала формировался с помощью секционированных планарных затворов, созданных по обеим сторонам канала. Электрические параметры полученных структур, измеренные при температурах до 1.5 K, подтвердили эффективность примененного метода для создания изолирующих областей с латеральными размерами ~ 10 нм. DOI: 10.21883/FTP.2017.11.45106.20

Quasi-one-dimensional semiconductor structures with a variable longitudinal potential profile are fabricated by pulse power nanolithography, which is carried out using an atomic force microscope. Structures are fabricated on the basis of AlGaAs/GaAs heterostructures with a deep (130 nm from the surface) twodimensional electron gas. The channel potential profile is formed with the help of sectioned in-plane gates formed on both channel sides. The electrical parameters of the structures measured at temperatures down to 1.5 K confirmed the efficiency of the applied method to fabricate insulating regions with lateral sizes of ~10 nm.

This paper reviews the literature concerning the specifics of creating Ohmic contacts to AlGaAs/GaAs heterostructures with a 2D electron gas with high electron mobility. The process of annealing the contacts based of the Ni/Au/Ge system is considered, and the recommended parameters of the metalization layers are borrowed from the literature. This process allows reproducible fabrication of Ohmic contacts with a low electrical resistance to temperatures below 4K. Several mechanisms are analyzed which could result in the experimentally observed dependence of the contact parameters on crystallographic orientation. A method of contact fabrication with Au/ Ge/Pd metallization is described for which the contact is formed by mutual diffusion and interaction of the metals and the semiconductor in the solid phase at temperatures below 200 °C. This provides for high composition homogeneity of the contacts, a smooth metal / semiconductor boundary and can reduce the effect of orientation on the electric characteristics of the contact.