A. L. Aseev

Nanotechnologies in semiconductor electronics

The various technologies for fabrication micro- and nanosized systems included semiconductor, metal and insulator structures are reviewed on the base of the data obtained in Novosibirsk Institute of Semiconductor Physics. Main attention is devoted to development of method of molecular beam epitaxy, silicon-on-insulator fabrication process, electron beam lithography and scanning probe nanolithography.

Aharonov-Bohm Oscillation Amplitude in Small Ballistic Interferometers

Small-radius (110 nm) ring interferometers were fabricated by the local anodic oxidation of AlGaAs/GaAs heterostructures containing 2D electron gas. Measurements and modeling show that a small ring asymmetry, which is detected by an atomic force microscope, leads to a small amplitude of Aharonov-Bohm oscillations, while a stronger asymmetry completely suppresses these oscillations.

Single-electron charging of triangular quantum dots in a ring interferometer

Small-size semiconductor ring interferometers operating in the Coulomb blockade regime have been experimentally and theoretically studied. The conductance as a function of the gate voltage exhibits narrow quasiperiodic peaks, which are further split into doublets. Based on the experimental structural data, a three-dimensional electrostatic potential, the energy spectrum, and the single-electron transport in the interferometer were modeled. The electron system can be divided into two triangular quantum dots connected by single-mode microcontacts to each other and to the reservoirs. A model of quantum dot charging in this system is proposed that explains the appearance of doublets in the conductance-gate voltage characteristics.

Quantum Hall liquid-insulator and plateau-to-plateau transitions in a high mobility 2D electron gas in an HgTe quantum well

The results of a study of the magnetic-field-induced quantum Hall liquid-insulator transition and the plateau-to-plateau transition in a high mobility two-dimensional electron gas in an HgTe quantum well are reported. The applicability of the universal scaling models (such as the universal critical exponent description and the semicircle model) for the description of these transitions is analyzed. It is shown that neither of these descriptions is completely adequate for the system under study.

A new memory element based on silicon nanoclusters in a ZrO2 insulator with a high permittivity for electrically erasable read-only memory

The write and erase function and the data retention characteristics of a memory element designed to be used in electrically erasable read-only memory and based on a silicon-oxide-(silicon dot)-oxide-polysilicon structure, in which either a SiO2 insulator or a ZrO2 high-permittivity insulator are used as blocking oxides, are simulated. It is established that the use of the high-permittivity insulator gives rise to a number of effects: spurious injection from poly-Si is reduced; the electric field in the tunneling oxide increases; it becomes possible to increase the thickness of the tunneling insulator and, consequently, to increase the data retention time; and lower voltages for the write and erase functions can be used. Programming with a pulse of ±11 V possessing a width of 10 ms makes it possible to retain a memory window of ∼3 V for 10 years.

Quantum interferential Y-junction switch.

We report the observation of the Fermi energy controlled redirection of the ballistic electron flow in a three-terminal system based on a small (100 nm) triangular quantum dot defined in a two-dimensional electron gas (2DEG). Measurement shows strong large-scale sign-changing oscillations of the partial conductance coefficient difference G(21) - G(23) on the gate voltage in zero magnetic field. Simple formulas and numerical simulation show that the effect can be explained by quantum interference and is associated with weak asymmetry of the dot or inequality of the ports connecting the dot to the 2DEG reservoirs. The effect may be strengthened by a weak perpendicular magnetic field. We also consider an additional three-terminal system in which the direction of the electron flow can be controlled by the voltage on the scanning gate microscopy (SGM) tip.

NANOPATTERNING OF SILICON-BASED NANOSTRUCTURES BY AFM PROBE

Atomic force and reflection electron microscopes have been applied to investigate tip-induced local anodic oxidation of the titanium and silicon films. The number of parameters such as applied voltage, oxidation time, relative humidity and host material was under consideration. The special treatments were applied to reduce the roughness of the studied surfaces achieving the average roughness of the surface less than one angstrom. Some examples of nanostructures fabrication are demonstrated.

Efficient single-photon emitters based on Bragg microcavities containing selectively positioned InAs quantum dots

A semiconductor Bragg microcavity structure for single photon emitters is designed and implemented. The design provides the efficient current pumping of selectively positioned InAs quantum dots within a micrometer-size aperture, high external quantum yield, and low divergence of the emitted radiation.

Introscopy of quantum nanoelectronic devices

Semiconductor nanoelectronic quantum devices are one of the achievements of contemporary physics and laboratory nanotechnologies. Short thin current channels are formed by electric fields in the plane of the two-dimensional electron gas deep below the surface of these devices. The real distribution of the electric fields and the picture of quantum transport in the channels can be reconstructed only by the combined experimental and numerical probing of the nanostructure. In this work, a concept of numerical introscopy, a method which is a natural continuation of the structural and electrophysical diagnostics and helps restore the picture of hidden processes and phenomena in nanostructures, is introduced on the basis of a few examples of the fabrication and investigation of nanodevices.

Modification of silicon-on-insulator structures under nano-scale device fabrication

Based on the characterization of the ultrathin silicon-on-insulator (SOI) test structures, the effects of charge at the interface between the top silicon layer and the buried oxide (bonded interface) are studied during different technology steps (thinning of the top silicon layer and plasma etching). SOI structures were fabricated by wafer bonding and hydrogen slicing technology. An increase in the charge with the thinning of the top silicon layer and introduction of the mobile charge or the slow interface states after the plasma etching were found for the SOI structures. The conductance oscillations have been observed at room temperature in the ultrathin silicon layers due to formation of tunnel barriers for one type of carriers caused by charge fluctuation.