Microwave-induced transient parametric gratings

We propose a new method for the formation of light-induced transient gratings in microwave-biased semiconductor crystals that exhibit a negative differential resistivity. Nonuniform heating of the electron gas in alternating electric fields induces spatially periodic modulation of the refractive index with spacing that is tunable by the external field frequency. Numerical simulations performed on a bulk GaAs sample prove that transient parametric gratings of both free-carrier and electro-optic origin can be triggered by a spatially modulated light pattern or by uniform photoexcitation.     

Observation of a light-induced nonohmic current in a toroidal-moment-possessing nanostructure

We report on the first observation of light-induced nonohmic current in a semiconductor nanostructure. The effect is revealed in an unbiased asymmetric InAs quantum well under excitation by far-infrared laser radiation in the presence of a tilted magnetic field. It is interpreted in terms of a nonzero toroidal moment of a two-dimensional electron gas.     

Effect of electric field on the magnetic characteristics of a ferromagnetic nanosemiconductor

A theory is developed to describe the effect of an electric field on the magnetization of a thin ferromagnetic semiconductor plate. It is shown that the magnetic moment density is nonuniform under these conditions and that the total magnetic moment and its density depend on the electric field and the temperature. An electric field is found to increase the Curie temperature, and an inflection point is detected in the temperature dependence of the derivative of the total magnetic moment with respect to temperature.     

Magnetotransport in a semconductor superlattice with transverse magnetic field

Magnetotransport in a semiconductor superlattice (SL) under transverse magnetic field has been investigated. It is shown that in weak magnetic and electric fields there is negative magnetoresistivity along the SL layers and positive magnetoresistivity along the SL axis. The Hall resistivity is much less than the usual semiconductor value. With an increase of electric field, there appears a negative differential conductivity (NDC) along the SL layers, and the Hall voltage depends nonlinearly on current density. In higher electric field, destroying the miniband structure, the magnetoresistivity along the SL axis is negative. The magnetoresistivity along the SL axis in strong magnetic field is positive for any current density. The Hall resistivity in strong magnetic (electric) field equals the classical value.     

Soliton envelope modulation instability and amplification in a semiconductor with striction-type electromechanical coupling

Modulation instability is considered for an electromagnetic wave incident on a ferroelectric semiconductor. The instability conditions coincide with those for drift and parametric sound excitation by an external electric field. Electrosound envelope solitons can exist in such a semiconductor. A study is made on how a steady electric field affects the envelope soliton propagation, and an amplification criterion is derived.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 93–97, November, 1990.     

On the hopping conduction mechanism of amorphous semiconductors in a strong electric field

The theory of the hopping conduction by the radiative tunnel transitions (RTT) in a strong electric field is applied to amorphous silicon and germanium. On the basis of numerical estimations we suggest that the relative contribution of the RTT mechanism into the total strong electric field hopping conductivity of an amorphous semiconductor could be significant.     

Spectral photoresistive effect of the field in CdS crystals at low temperatures

The influence of the surface electric field on the low-temperature (T=77 K) photoconductivity spectra of CdS crystals in the region of exciton and interband transitions is experimentally studied by the field-effect method. The photoconductivity spectra of a semiconductor are numerically calculated in the framework of a model allowing for the dependence of the surface recombination rate of nonequilibrium charge carriers on the surface electric field. It is demonstrated that the surface electric field plays a decisive role in the formation of the fine spectral structure associated with the excitons. A correlation between the type of fine structure and the surface bending of the energy bands is revealed. It is shown that the surface electric field can be evaluated from the shape of the low-temperature photoconductivity spectrum of the semiconductor.     

Optical Stark effect in a quantum dot: ultrafast control of single exciton polarizations

We report the first experimental study of the optical Stark effect in single semiconductor quantum dots (QD). For below band gap excitation, two-color pump-probe spectra show dispersive line shapes caused by a light-induced blueshift of the excitonic resonance. The line shape depends strongly on the excitation field strength and is determined by the pump-induced phase shift of the coherent QD polarization. Transient spectral oscillations can be understood as rotations of the QD polarization phase with negligible population change. Ultrafast control of the QD polarization is demonstrated.     

Interband light absorption by a semiconductor in a pulsing electric field

The light absorption by a semiconductor, placed in a pulsing electric field of arbitrary amplitude and pulse duration is considered. The calculation of the absorption coefficient is carried out on the ground of the effective mass method for direct optical transitions between two simple parabolic bands. The calculated absorption coefficient is valid for photon energies both greater and lesser than the semiconductor forbidden bandwidth.     

Decay of charged complexes in quasi-2D semiconductor structures in the presence of electric fields

An analytical approach to the problem of a charged and weakly bound complex in a quasi-two-dimensional semiconductor structure subject to an electric field is developed. Using the zero-range potential method the red shift of the energy level of the extra electron and the detachment rate of the complex, both induced by the electric field, are calculated and provided in an explicit form. It is shown that the 2D charged complex is far more stable than we take in the analogous system in the bulk semiconductor in the presence of the electric field. Explicit values for donors in InGaN layers are presented.     

Microscopic view of charge injection in an organic semiconductor

We have measured the chemical potential and capacitance in a disordered organic semiconductor by electric force microscopy, following the electric field and interfacial charge density microscopically as the semiconductor undergoes a transition from Ohmic to space-charge limited conduction. Electric field and charge density at the metal-organic interface are inferred from the chemical potential and current. The charge density at this interface increases with electric field much faster than is predicted by the standard diffusion-limited thermionic emission theories.     

正对电极结构碳化硅光导开关的电路模型

利用SilvacoTCAD软件,在532 nm激光辐照下,对正对电极结构6H-SiC光导开关（SiC-PCSS）瞬态电流电场的分布及不同光功率下的伏安特性进行了仿真。结果表明:载流子速率在强场下达到饱和,并且电流电场在主要电流区域沿垂直于激光辐照方向均匀分布。提出SiC-PCSS电路模型的建模依据,可以近似条件化简得到PCSS电阻一般表达式的解,建立SiC-PCSS载流子迁移率随电场变化的PSpice模型,分析讨论了外电路参数对SiC-PCSS导通过程的影响。该模型模拟结果与已有实验结果吻合良好。     

Effect of Electric Field on Spin Polarized Current in Ferromagnetic/Organic Semiconductor Systems

Considering the special carriers in organic semiconductors, the spin polarized current under electric field in a ferromagnetic/organic semiconductor system is theoretically studied. Based on the spin-diffusion theory, the current spin polarization under the electric field is obtained. It is found that electric field can enhance the current spin polarization.     

Peculiarities of electron spectrum rearrangement for the double-well heterostructure GaAs/AlGaAs with a variable dimensionality of electronic states in an external electric field

Peculiarities of the electron spectrum rearrangement for the double-well heterostructure GaAs/AlGaAs with a variable dimensionality of electronic states in an external electric field are investigated theoretically and experimentally. The structure is an important part of the active element of a quantum-well unipolar semiconductor laser proposed by the authors earlier. The possibility of controlling the dimensionality of the lower laser subband in such an active element by an external electric field is demonstrated.     

2D bifurcations in a system of interacting quantum molecules in a metamaterial matrix

The influence of an electric field on 1D and 2D tunneling in a quantum molecule located in dielectric and metamaterial (with effective negative permittivity) matrices at a finite temperature has been theoretically investigated within the one-instanton approximation. It is shown that the stable mode of 2D bifurcations in a metamaterial matrix can be implemented in a much narrower range of parameters in comparison with conventional dielectric matrices. The dependence of the probability of 1D dissipative tunneling on the strength of an external electric field is qualitatively compared with the experimental tunnel I-V characteristic of semiconductor (InAs/GaAs) quantum dots.     

Investigation of velocity overshoot behavior in p-i-n GaAs semiconductor: The contribution of internal electric field

In this work, we present the investigation of the velocity overshoot behavior in p-i-n GaAs semiconductor based on the ensemble Monte Carlo simulations. Our simulations with high-resolution of time and spatial show that the velocity overshoot effect is originated from internal electric field caused by the difference of carrier density. And this effect is dependent not only on the carrier density but also on temperature. Furthermore, we have observed the velocity relaxation effect which was not recognized before because the external electric field is too high comparing to the internal electric field in semiconductor. We point out that the velocity relaxation can be seen as a damping oscillation in which the damping velocity depends strongly on carrier density but not temperature.     

Scanning of a laser beam and purification of materials through the use of light-induced particle drift in semiconductors

The light-induced drift of electrons, light-absorbing impurities, and defects in II-VI semiconductors is investigated experimentally, along with some potential practical applications of the phenomenon. It is shown that the light-induced drift of electrons induces a very pronounced change in the refractive index, |Δn|∼0.01, and can be used to implement effective scanning of nanosecond and picosecond laser pulses through frustration of total internal reflection. The light-induced drift of absorbing particles increases their density in the surface layer of the crystals, and this effect can be exploited in semiconductor technology. Zh. Tekh. Fiz. 68, 121–124 (April 1998)     

Helical instability of a semiconductor plasma in silicon wafers at 77 K

This paper reports an analysis of the experimental results on how the threshold electric field intensity required to excited helical instability of a semiconductor plasma in wafers of p-silicon depends on the magnitude of magnetic induction. Also cited are data on the dependence of the threshold frequency on electric field intensity. The variations of the amplitude of the alternating current, caused by the development of helical instability, with electric field intensity and magnetic induction well above the instability excitation threshold are examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 54–60, August, 1991.     

The flow of electric current through a semiconductor with spatially periodical parameters

It is shown that in a semiconductor with spatially periodical concentration of impurities it is possible to attain a situation when the conductivity varies under d.c. applied electric field periodically with time, i.e. oscillations of current can occur. The occurence of such oscillations is the consequence of the inertia of processes taking place in the semiconductor.     

Effect of the field of a nonlinear electromagnetic wave on the shape of a soliton in a semiconductor superlattice

The effect of the electric component of the field of a high-frequency (HF) nonlinear electromagnetic (EM) wave on the propagation of a solitary EM wave (soliton) in a quantum semiconductor superlattice is studied. It is noted that in the collisionless approximation, the solution of the modified sine-Gordon equation corresponding to the amplification of an EM pulse that, with allowance made for interminiband electron transitions, transforms into a dissipative soliton is possible. The effect of electron collisions with irregularities of the crystal lattice on the soliton dynamics under the action of the field of a HF nonlinear wave is considered. The condition for an increase in the traveling time of the solitary wave is found.