Electron Systems In Semiconductors Research Articles

Measurements of the magnetic properties of conduction electrons

We consider various methods and techniques that are used in experimental condensed matter physics for measuring electron magnetization and susceptibility. The list of considered methods for macroscopic measurements includes magnetomechanical, electromagnetic, modulation-type, and thermodynamic methods based on chemical potential variation measurements. We also consider local methods of magnetic measurements based on the spin Hall effect and nitrogen-substituted vacancies (NV centers). Scanning probe magnetometers–microscopes are considered, such as the magnetic resonance force microscope, SQUID microscope, and Hall microscope. The review focuses on the electron spin magnetization measurements in nonmagnetic materials and systems, particularly in low-dimensional electron systems in semiconductors and in nanosystems that have come to the forefront in recent years.

Измерение магнитных свойств электронов проводимости

We consider various methods and techniques for measuring electron magnetization and susceptibility, which are used in experimental condensed matter physics. The list of considered methods for macroscopic measurements includes magnetomechanic, electromagnetic, modulation-type, and also thermodynamic methods based on the chemical potential variation. We also consider local methods of magnetic measurements based on the spin Hall effects and NV-centers. Several scanning probe magnetometers-microscopes are considered, such as magnetic resonance force microscope, SQUID-microscope, and Hall microscope. The review focuses on the spin magnetization measurements of electrons in non-magnetic materials and artificial systems, particularly, in low-dimensional electron systems in semiconductors and in nanosystems, which came to the forefront in recent years.

Anisotropic Rashba effect and charge and spin currents in monolayer BiTeI by controlling symmetry

The manipulation of Rashba effects in two-dimensional (2D) electron systems in semiconductors is highly desirable for controllable electronic and optical applications. Here, combining a first-principles investigation and model analysis, we use uniaxial stress to control monolayer BiTeI as a Rashba 2D semiconductor. We find that the stress-driven electron system can be described by an effective anisotropic Rashba model including all three Pauli matrices, and uniaxial stress allows an out-of-plane spin component because of rotational symmetry breaking. When appropriate electron carriers are introduced into the monolayer, an in-plane electric field can induce a charge current and three spin current components (including that based on the out-of-plane spin) because of the reduced symmetry. Therefore, uniaxial stress can be used to control Rashba 2D electron systems such as monolayer BiTeI for promising spintronic devices.

An ultrathin integrated nanoelectromechanical transducer based on hafnium zirconium oxide

The monolithic integration of electromechanical transduction at the nanoscale with advanced CMOS is among the most important challenges of semiconductor electronic systems to leverage the multi-domain sensing, actuation, and resonance properties of nano-mechanical systems. Here we report on the demonstration of vibrating devices enabled by atomically engineered ferroelectric Hf0.5Zr0.5O2 thin films with a variety of mechanical resonance modes with frequencies (f0) between 340kHz - 13GHz and frequency-quality (Q) factor products (f0 x Q) up to 3.97 x 10^12. Experiments based on electrical and optical probing elucidate and quantify the role of the electrostrictive effect in the electromechanical transduction behavior of the Hf0.5Zr0.5O2 film. We further demonstrate the role of nonlinear electromechanical scattering on the operation of Hf0.5Zr0.5O2 transduced resonators. This investigation also highlights the potential of atomically engineered ferroelectric Hf0.5Zr0.5O2 transducers for new classes of CMOS-monolithic linear and nonlinear nanomechanical resonators in centimeter- and millimeter-wave frequencies.

Probing Electron Mobility of Monolayer MoS2 Field‐Effect Transistors in Aqueous Environments

AbstractAtomically thin layered 2D semiconductors have inspired intense interest in building hybrid liquid–semiconductor electronic systems for next‐generation biological/chemical sensing applications. There remains, however, a lack of understanding of the electrical characteristics of 2D materials in aqueous environments and, thereby, much useful information for advancing the development of such emerging sensor systems. In this study, the effects of aqueous environments on the field‐effect electron mobility (µFE) of monolayer molybdenum disulfide (MoS2) field‐effect transistors (FETs), using various operational modes (back‐gating, liquid‐gating, and dual‐gating), are explored at room temperature. The value of µFE of the MoS2 exposed to deionized (DI) water is much greater than that treated merely under ambient conditions, presumably the result of a dielectric screening effect. When the DI water is changed to a biologically compatible buffer (0.01 or 0.1 m potassium phosphate buffer) at pH 7, the value of µFE decreases significantly. Further investigation into the possible origin of the degraded mobility suggests that the ions in the aqueous solutions play an important role as additional scatterers. This report should enhance the understanding of the mechanisms of mobility scattering in liquid–semiconductor 2D FET systems for applications in hybrid electronics, bioelectronics, and nanosensors.

Enhanced electron-phonon coupling for a semiconductor charge qubit in a surface phonon cavity.

Electron-phonon coupling is a major decoherence mechanism, which often causes scattering and energy dissipation in semiconductor electronic systems. However, this electron-phonon coupling may be used in a positive way for reaching the strong or ultra-strong coupling regime in an acoustic version of the cavity quantum electrodynamic system. Here we propose and demonstrate a phonon cavity for surface acoustic waves, which is made of periodic metal fingers that constitute Bragg reflectors on a GaAs/AlGaAs heterostructure. Phonon band gap and cavity phonon modes are identified by frequency, time and spatially resolved measurements of the piezoelectric potential. Tunneling spectroscopy on a double quantum dot indicates the enhancement of phonon assisted transitions in a charge qubit. This encourages studying of acoustic cavity quantum electrodynamics with surface phonons.

Strongly correlated two-dimensional plasma explored from entropy measurements.

Charged plasma and Fermi liquid are two distinct states of electronic matter intrinsic to dilute two-dimensional electron systems at elevated and low temperatures, respectively. Probing their thermodynamics represents challenge because of lack of an adequate technique. Here, we report a thermodynamic method to measure the entropy per electron in gated structures. Our technique appears to be three orders of magnitude superior in sensitivity to a.c. calorimetry, allowing entropy measurements with only 10(8) electrons. This enables us to investigate the correlated plasma regime, previously inaccessible experimentally in two-dimensional electron systems in semiconductors. In experiments with clean two-dimensional electron system in silicon-based structures, we traced entropy evolution from the plasma to Fermi liquid regime by varying electron density. We reveal that the correlated plasma regime can be mapped onto the ordinary non-degenerate Fermi gas with an interaction-enhanced temperature-dependent effective mass. Our method opens up new horizons in studies of low-dimensional electron systems.

The Induced Physical Effects on the Semiconductor Electronics under Electromagnetic Pulse

The response of the electronic devices subjected to the Electromagnetic Pulse (EMP) effect is a complex problem. The damage to the electronic device due to the EMP is one of the main failure mechanisms in the modern semiconductor electronic systems. The study of the induced physical effects on the semiconductor electronics in this particular aspect of damage is applicable not only to EMP problems but is also applicable when the high transient voltages appear in the circuits whether the pulse origin is EMP, or a transient transform within the system itself, which we will also address briefly. 

Electron–acoustic-phonon energy-loss rate in multicomponent electron systems with symmetric and asymmetric coupling constants

We consider electron-phonon (\textit{e-ph}) energy loss rate in 3D and 2D multi-component electron systems in semiconductors. We allow general asymmetry in the \textit{e-ph} coupling constants (matrix elements), i.e., we allow that the coupling depends on the electron sub-system index. We derive a multi-component \textit{e-ph}power loss formula, which takes into account the asymmetric coupling and links the total \textit{e-ph} energy loss rate to the density response matrix of the total electron system. We write the density response matrix within mean field approximation, which leads to coexistence of\ symmetric energy loss rate $F_{S}(T)$ and asymmetric energy loss rate $F_{A}(T)$ with total energy loss rate $ F(T)=F_{S}(T)+F_{A}(T)$ at temperature $T$. The symmetric component F_{S}(T) $ is equivalent to the conventional single-sub-system energy loss rate in the literature, and in the Bloch-Gr\"{u}neisen limit we reproduce a set of well-known power laws $F_{S}(T)\propto T^{n_{S}}$, where the prefactor and power $n_{S}$ depend on electron system dimensionality and electron mean free path. For $F_{A}(T)$ we produce a new set of power laws F_{A}(T)\propto T^{n_{A}}$. Screening strongly reduces the symmetric coupling, but the asymmetric coupling is unscreened, provided that the inter-sub-system Coulomb interactions are strong. The lack of screening enhances $F_{A}(T)$ and the total energy loss rate $F(T)$. Especially, in the strong screening limit we find $F_{A}(T)\gg F_{S}(T)$. A canonical example of strongly asymmetric \textit{e-ph} matrix elements is the deformation potential coupling in many-valley semiconductors.

Shining light on electrons under extreme conditions

Strongly-correlated two-dimensional (2D) electron fluids occur in artificial semiconductor heterostructures of high perfection that are subjected to quantizing magnetic fields. Under conditions of high magnetic fields, low temperatures in the millikelvin range and low electron density, the 2D quantum fluids display dispersive low-energy collective excitations that represent time- and space-dependent oscillations in the charge and/or the orientations of spin. These collective modes manifest fundamental interactions that are responsible for electron correlation. Studies of low-lying collective excitation modes play pivotal roles in the low-temperature phases of the electron liquids and offer venues of studying energetics, coherence, magnetization, instabilities and quantum phase transitions of the 2D system. In 1978 a proposal by Burstein, Pinczuk and Buchner suggested that resonant inelastic light scattering methods would have the sensitivity required to study elementary excitations of 2D electron systems in semiconductors. We review here recent light scattering results obtained from 2D electron fluids in semiconductor quantum structures under extreme conditions of low temperature and large magnetic field. In these experiments, resonant inelastic light scattering methods probe fundamental behaviors due to interactions with a sensitivity that will keep light scattering studies at the frontiers of research of quantum fluids in low dimensional electron systems.

Magneto-optics of strongly correlated two-dimensional electrons in single heterojunctions

Abstract Investigations of two-dimensional (2D) electron systems in semiconductors subjected to a strong perpendicular magnetic field with the use of photoluminescence are reviewed. The foundation of the optical spectroscopy method using the radiative recombination of 2D electrons with photoexcited holes bound to acceptors in a δ-doped monolayer in GaAs/Al x Ga1-x As single heterojunctions is presented. Optical spectroscopy studies of the energy spectra of 2D electrons imposed on transverse magnetic fields in the regimes of the integer and fractional quantum Hall effects are discussed. The relationship between the mean energy of the 2D electron gas and the first moment of their radiative recombination is analysed. It is shown that the magnetic field dependence of the first moment provides a method to measure the cyclotron, enhanced spin and quasiparticle energy gaps at the same time. Therefore it is shown how magneto-optics ‘see’ the ground state of interacting 2D electrons in the extreme quantum limit an...

FAST ALGORITHM FOR COMPUTATIONAL STUDY OF DEEP LEVEL PHOTOLUMINESCENCE SPECTRA

An algorithm for fast calculation of theoretical deep level photoluminescence (PL) lineshapes is presented. The algorithm can be used for effective comparison with experimental spectra in cases of bulk photoluminescence. The method was expanded and for the cases of deep level photoluminescence in quasi-two and quasi-one dimensional electron systems in semiconductors.

Light scattering from two-dimensional electron systems in strong magnetic fields

Resonant light scattering has been shown to be a sensitive and versatile technique for the study of two-dimensional electron systems in semiconductors. We have extended the technique by the imposition of strong magnetic fields perpendicular to the two-dimensional planes in modulation doped AlGaAsGaAs heterostructures. At modest magnetic fields, the polarized spectra show a line which we interpret as forbidden cyclotron resonance, and a higher frequency mode probably interpretable as the upper hybrid or magnetoplasma mode. Both modes represent in-plane motion: scattering from in-plane degrees of freedom has not been observed in zero field. No known theory accounts for these observations. We summarize these results, and then discuss the properties of the magnetoplasma mode, suggesting its importance in the study of two-dimensional electron ordering at high fields.

Light scattering by two-dimensional electron systems in semiconductors

Light scattering by two-dimensional electron systems in semiconductors

Light scattering by two-dimensional electron systems in semiconductors

We discuss recent work on resonant inelastic light scattering by multilayer and single-layer two-dimensional electron gases in semiconductors. The multilayer systems occur in doped multiple -quantum-well GaAs(AlGa)As heterostructures. The single layers are at doped (GaAs-(AlGa)As heterojunctions; and at InAsMOS interfaces. Light scattering spectra display a wealth of information related to intersubband excitations. We consider in detail the depolarization field effects of collective electron-electron interactions: and correlations between spectral line shapes and transport properties.