On the temperature and field dependences of the effective surface mobility in MIS structures

A physical model establishing a relation between the surface density of the free electronic charge in an inversion layer and the surface density of stationary (localized) electrons trapped in surface states at a semiconductor-insulator interface is constructed. It is established that at moderately low temperatures this relation is close to a direct proportionality. The presence of surface states, which localize some of the surface electronic charge, is manifested as a decrease in the effective electron mobility in the channel of a MIS transistor. The well-known decrease of the surface mobility with increasing transverse electric field is attributed to field-induced variations in the position of the percolation level that separates bound electronic states from free states. Fiz. Tekh. Poluprovodn. 32, 748–751 (June 1998)     

Thermoelectric power of the n-InSb in a transverse quantizing magnetic field at a large temperature gradient

The thermoelectric power of the n-type indium antimonide was studied in the transverse magnetic field (0–80 kOe) at T _aV =160 K and different temperature gradients. It was found that the electron component of the thermoelectric power at a small temperature gradient is consistent with the theory that takes into account the electron spin, whereas, for a large temperature gradient, the value determined by the variation of the Benedicks thermoelectric power in the magnetic field is added to this component.     

Relaxation of photoinduced metastable states in a-Si:H films deposited at high temperatures

The results of an experimental study of dark-conductivity kinetics in a-Si:H after short-term and long-term illumination, are presented. The films were deposited at temperatures in the range T _s=300–390 °C. Data on relaxation of the photoinduced metastable states were found to correlate with the Fermi-level position. Fiz. Tekh. Poluprovodn. 32, 1269–1271 (October 1998)     

Drain noise in MOSFETs at zero drain bias as a function of temperature

The noise in MOSFETs at zero drain bias is found to be somewhat larger than the thermal noise of the output conductance g_do at that bias. The effect is most pronounced at 300°K and has practically disappeared at 77°K. The effect is attributed to the large transverse field at the surface of the channel; the temperature dependence of the effect is as yet unexplained.     

A study of flicker noise in MOS transistors operated at room and liquid helium temperatures

A study of flicker noise in MOS transistors operated in the linear and non linear regions at room and liquid helium temperatures is proposed. Besides, a theoretical analysis of the drain current noise characteristics is developed in the framework of the mobility fluctuation model as well as of the carrier number fluctuation model. It is shown experimentally that a close correlation between the drain current spectral density and the transconductance squared dependencies with gate voltage (or drain current) and drain voltage is observed in our devices both at room and liquid helium temperatures. Therefore, it is concluded that the carrier number fluctuation model is not only applicable to MOS devices operated at room temperature but also at liquid helium temperature in ohmic and non ohmic regimes. In addition, peculiarities of the drain current noise related to the appearance of a kink effect at liquid helium temperature in the saturation current characteristics are also discussed.     

8C9--Observation of cooperative effects and determination of the electron and ion temperatures in a plasma from the scattering of a ruby laser beam

Observations have been made on the forward scattering of aQ-spoiled ruby laser beam from a hydrogen plasma which show clearly both the central ion peak and the satellites due to cooperative interaction between the ions and electrons. In a separate experiment on a large θ-pinch producing a high temperature deuterium plasma, the ion peak has been resolved and values obtained for both the electron and ion temperatures in the plasma. Preliminary values of the ion temperature are consistent with a thermonuclear origin for the neutron emission observed.     

The staebler-wronski effect and temperature dependences of photoconductivity in p-type a-Si:H

Temperature dependences of the photoconductivity of boron doped a-Si:H films both prior to and after prolonged illumination were studied. It was found that the photoconductivity of films under study in the temperature range 200–300 K (intermediate temperatures) is independent of the doping level and the concentration of deep recombination centers (dangling bonds). A model of recombination is used to explain the experimental results; according to this model, the occupancy function of neutral dangling bonds in p-type a-Si:H (and, consequently, also the photoconductivity) is determined by the parameters of the states of the valence band tail and is independent of the doping level and of the total concentration of dangling bonds.     

Study of surface morphology in GaAs by hydrogen and helium implantation at elevated temperature

In this work, the surface morphology and internal defect evolution process of GaAs substrates implanted with light ions of different fluence combinations are studied. The influence of H and He ions implantation on the atomic mechanism of the blister phenomenon observed after annealing is investigated. Raman spectroscopy is used to measure the surface stress change of different samples before and after implantation and annealing. Optical microscopy and atomic force microscopy are used to characte...     

Effect of temperature on the thermodynamic density of states in a quantizing magnetic field

The dependence of the density of energy states (N _s ) on temperature in quantizing magnetic fields is studied. It is shown that, as temperature is increased, the Landau levels are blurred as a result of thermal widening and the quantities N _s are transformed into the density of states as in the absence of a magnetic field. The temperature dependence of the distribution of the density of energy states in high magnetic fields for semiconductors is considered using a mathematical model. It is shown that the continuous spectrum of density of states measured at liquid-nitrogen temperature is transformed into discrete Landau levels at lower temperatures. Mathematical simulation of the processes with the use of experimental data for the continuous spectrum of the density of states makes it possible to calculate the discrete Landau levels. Experimental results obtained for PbS are analyzed using the suggested model. The density of states at low temperatures is calculated from data on high-temperature N _s .     

Bias temperature instabilities in 4H SiC metal oxide semiconductor field effect transistors: Insight provided by electrically detected magnetic resonance

We present insight with regard to the physical mechanisms of negative bias temperature instabilities (NBTI) in 4H SiC based metal oxide semiconductor field effect transistors (MOSFETs) based upon electrically detected magnetic resonance measurements (EDMR). Most of this insight results from EDMR studies not directly focused upon NBTI but studies more broadly focused upon two fundamental questions. (1) What as-processed defects are present at and near the SiC/oxide interface? (2) How does the presence of oxide charge alter electrically active defects at the SiC/dielectric interface? We compare the SiC results to magnetic resonance studies of bias temperature instabilities in silicon based devices. Although our analysis admittedly provides only a partial understanding of the phenomena in SiC devices, the analysis does allow for some reasonably definitive conclusions. The NBTI phenomena in 4H SiC MOSFETs are certainly different than in Si based MOSFETs. (1) Interface dangling bonds do not appear to play a significant role in SiC MOSFET interface traps under multiple circumstances, suggesting strongly that they are not significant contributors to NBTI. (2) Although oxide defects, almost certainly including the well-known E′ family of oxide traps, play an important role in SiC device NBTI, other defects, surprisingly including defects within the SiC substrate, are also involved.     

The temperature dependence of the thermopower of the InSb Corbino disc in a quantizing magnetic field

Thermopower of the Corbino disc made of InSb with n ₇₇ = 2 × 10¹⁴ cm^?3 in a transverse magnetic field as high as 30 kOe at temperatures of 60, 67, and 80 K is studied. It is established that the diffusion fraction of thermopower in a quantizing magnetic field rises according to the power law H ^2.2 at all mentioned temperatures. By the magnitude of saturation thermopower α_xx(∞) in a high field, the scattering mechanism of charge carriers is determined. It is established that in a temperature region of 60–80 K, the electrons are scattered by acoustic phonons.     

Resonant response of a FET to an AC signal: influence of magnetic field, device length, and temperature

A theoretical investigation is made of the response of a field-effect transistor (FET) to an incoming electromagnetic radiation in the presence of a perpendicular, weak magnetic field. The influence of an external friction due to electron scattering by impurities and/or phonons, and of the internal friction due to electron-electron scattering, is taken into account. The treatment is valid for a nondegenerate electron gas in which the mean-free path for electron-electron scattering /spl lambda//sub ee/ is much smaller than the device length L and than the mean-free path due to collisions with impurities and/or phonons /spl lambda//sub coll/. These requirements, written as /spl lambda//sub ee//spl Lt/L/spl Lt//spl lambda//sub coll/, are fulfilled for magnetic fields sufficiently weak that Landau quantization is absent and the electron motion is described within the framework of hydrodynamics. It is demonstrated that a high-electron mobility transistor (HEMT), with a short (long) channel, yields a resonant (nonresonant) response to an ac signal induced by the incoming electromagnetic radiation at the plasma oscillation frequencies of the two-dimensional electrons in the device. Keeping the device length and temperature at control, an applied magnetic field can be tuned to achieve the desired effect on the response of the device. It is observed that the lower the temperature, i.e., the higher the mobility, the higher the responsivity of the device. Such response makes the FET a promising device for new types of sources, detectors, mixers, and multipliers. The HEMT-based devices should, in principle, operate at much higher frequencies than the conventional transit time-limited devices, since the plasma waves propagate much faster than electrons.     

中高温条件下激光冲击处理Ti-6Al-4V表面完整性变化

为了研究中高温条件下激光冲击处理对Ti-6Al-4V钛合金的表面完整性的影响,采用高功率、短脉冲Nd:YAG激光器对Ti-6Al-4V钛合金表面进行激光冲击,并将冲击后的钛合金试样分别置于400℃,500℃,550℃和600℃的温度下进行保温处理。从表面形貌、表面粗糙度、表面残余应力等方面分析了中高温条件下激光冲击处理对Ti-6Al-4V钛合金的表面完整性的影响。结果表明,激光冲击处理增大了Ti-6Al-4V钛合金的表面粗糙度,且热处理温度越高,Ti-6Al-4V钛合金的表面粗糙度越大;激光冲击处理显著提高了Ti-6Al-4V钛合金材料的表面残余压应力,随着温度的升高,残余压应力值降低。研究结果对了解和掌握Ti-6Al-4V钛合金的使用性能是有帮助的。     

Electromagnetic loss of fresh ice in microwave range at a temperature of 0°C

The decay of microwave radiation in melting fresh ice is studied in the millimeter wavelength range (at frequencies of 90 and 34 GHz). It is demonstrated that ice at a temperature of 0°C may exhibit a decrease in the electromagnetic loss up to several tens of percents presumably due to the streamflow in the presence of internal mechanical stress or complete absence of loss at different stages of melting.     

Circular polarization of the magnetic field in the WG modes ofresonance of a dielectric disc at microwave frequencies

The circular polarization of the magnetic field of the whispering-gallery (WG) modes of resonance of a dielectric disk resonator was tested in the evanescent-field region outside the dielectric material. Microwaves in the frequency range from 18 to 26.5 GHz (K-band) and the techniques of electron spin response (ESR) were used. The distribution of the electromagnetic fields was obtained with a finite element method, and it was found to be in agreement with the experimental results     

Magnetoresistance of layered semiconductors upon the scattering of charge carriers at impurity ions in a parallel magnetic field

The magnetoresistance of a semiconductor superlattice in a magnetic field directed perpendicular to its axis for the case of the scattering of charge carriers at impurity ions is calculated. It is demonstrated that the sign of the transverse magnetoresistance strongly depends on the band filling factor, the value of the magnetic field, and the ratios between the screening radius, cyclotron orbital radius, and superlattice constant. In a parallel magnetic field, the transverse magnetoresistance of a two-dimensional electron gas is positive in a strong field and negative in a weak field. The transverse magnetoresistance of a quasi-two-dimensional electron gas changes its sign due to the presence of a negative effective mass region in the miniband.     

Spectrum of an electron in a quantum well in high inclined magnetic field and high transverse electric field

The energy and wave functions of localized electron states in a quantum well in a high magnetic field arbitrarily oriented with respect to the layers of the structure, and a high transverse electric field are studied. The situation where the quantum-confined energy and the Landau energy are close to each other is considered. The evolution of the spectrum with varying orientation of the magnetic field over the entire angle range is studied.