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1.
Inelastic scattering processes of two-dimensional electron gas (2DEG) have been investigated in a inverted GaAs/n-AlGaAs heterojunction with self-organized InGaAs quantum dots (QDs) embedded near the 2DEG channel where the electron population in the QDs is controllable by the gate voltage Vg. By analyzing magnetoresistance, the inelastic scattering time τε have been evaluated as functions of Vg at 0.6, 0.8, 1.2, and 1.7 K. It is found that τε increases with Vg below 0.8 K and decreases above 1.2 K, which suggests that the dominant scattering mechanisms below 0.8 K and above 1.2 K are different. To interpret this behavior, we have calculated the inelastic scattering time theoretically. It is found that the experimental data are well explained by a theoretical model where a 2D electron is considered to be inelastically scattered both by the other 2D electrons and by the trapped electrons in QDs. It is also found that the 2DEG–2DEG scattering is dominant at low temperature, while the 2DEG-QDs scattering becomes important as the temperature increases. 相似文献
2.
Hot-carrier degradation for 90nm gate length LDD-NMOSFET with ultra-thin gate oxide under low gate voltage stress 下载免费PDF全文
The hot-carrier degradation for 90~nm gate length lightly-doped drain
(LDD) NMOSFET with ultra-thin (1.4~nm) gate oxide under the low gate
voltage (LGV) (at Vg=Vth, where Vth is the
threshold voltage) stress has been investigated. It is found that the
drain current decreases and the threshold voltage increases after the
LGV (Vg=Vth stress. The results are opposite to the
degradation phenomena of conventional NMOSFET for the case of this
stress. By analysing the gate-induced drain leakage (GIDL) current
before and after stresses, it is confirmed that under the LGV stress
in ultra-short gate LDD-NMOSFET with ultra-thin gate oxide, the hot
holes are trapped at interface in the LDD region and cannot shorten
the channel to mask the influence of interface states as those in
conventional
NMOSFET do, which leads to the different degradation phenomena from those of the
conventional NMOS devices. This paper also discusses the degradation in the
90~nm gate length LDD-NMOSFET with 1.4~nm gate oxide under the LGV stress at
Vg=Vth with various drain biases. Experimental results show that
the degradation slopes (n) range from 0.21 to 0.41. The value of
n is
less than that of conventional MOSFET (0.5-0.6) and also that of the long gate
length LDD MOSFET (\sim0.8). 相似文献
3.
The frequency (1-10 kHz) and temperature (80-350 K) dependences of the ac conductivity and dielectric constant of the V2O5-MnO-TeO2 system, containing two transition-metal ions, have been measured. The dc conductivity dc measured in the high-temperature range (200-450 K) decreases with addition of the oxide MnO. This is considered to be due to the formation of bonds such as V--O--Mn and Mn--O--Mn in the glass. The conductivity arises mainly from polaron hopping between V4+M and V5+ ions. It is found that a mechanism of adiabatic small-polaron hopping is the most appropriate conduction model for these glasses. This is in sharp contrast with the behaviour of the Mn-free V2O5-TeO2 glass, in which non-adiabatic hopping takes place. High-temperature conductivity data satisfy Mott's small-polaron hopping model and also a model proposed by Schnakenberg in 1968. A power-law behaviour ( ac = Aωs , with s < 1) is well exhibited by the ac conductivity σac data of these glasses. Analysis of dielectric data indicates a Debye-type relaxation behaviour with a distribution of relaxation times. The MnO-concentration-dependent σac data follow an overlapping large-polaron tunnelling model over the entire range of temperatures studied. The estimated model parameters are reasonable and consistent with changes in composition. 相似文献
4.
Mihaela Rusu Anton Airinei George G. Rusu LuminiŢA Marin Vasile Cozan Petronela RÂmbu 《Journal of Macromolecular Science: Physics》2013,52(7):1285-1297
Poly(azomethine sulfone)s were synthesized by reacting 4,4′-sulfonyl bis(4-chlorophenyl) with 2,2-bis(4-hydroxyphenyl)propane and azomethine bisphenol in different molar ratios. Thin films were deposited from solution onto glass substrates. Study of the temperature dependences of the electrical conductivity, σ, and Seebeck coefficient, S, were performed in the temperature range 300 K–500 K. Thermal activation energies of electrical conduction, Ea , calculated from these dependences, ranged between 1.50 eV and 1.85 eV. The values of Ea were smaller for polymers with extended conjugation systems. The possibility to use the polymers in thermistor technology is discussed. The aspect of the temperature dependences of σ and S shows that a model based on the energy band-gap representation can be successfully used for explaining the electronic transport mechanism in the higher temperature range. In the lower temperature range, the mechanism of the electrical conduction is discussed in terms of the Mott variable range hopping conduction. The values of some optical parameters (absorption coefficient, optical band gap, etc.) were determined from transmission spectra. 相似文献
5.
Saba Beg 《Phase Transitions》2016,89(2):167-179
New samples of the Bi2Zn0.1–xTixV0.9O5.35+x; 0.02 ≤ x ≤ 0.08 system have been synthesized through a standard solid-state reaction route. XRD analysis and differential thermal analysis have been used to characterize the phase structure of samples. The γ′ phase is stabilized to room temperature in all investigated samples. The electrical properties of the BIZNTIVOX system have been studied by using AC impedance spectroscopy. An AC impedance response as a function of frequency (20 Hz–1 MHz) has been used to investigate the electrical conductivity and the dielectric permittivity in the temperature range of 150 °C–700 °C. In this temperature range, the phase transition γ′ to γ has been observed in all the compositions studied. AC impedance spectroscopy indicates that the resistance of samples decreases with increase of temperature. The ionic conductivity of samples appeared as a two-line region in Arrhenius dependence. At 300 °C, the highest ionic conductivity is shown by the composition x = 0.05 (σ300 = 1.35 × 10?4 S cm?1). 相似文献
6.
The amplitude of the quantum oscillations in the magnetoconductance of a silicon inversion layer has been studied as a function of gate voltage Vg, for different values of the temperature T, applied magnetic field strength H and substrate bias Vs. By analyzing the amplitude of the oscillations at fixed Vg and Vg as a function of T and H, the dependence of the cyclotron effective mass m1 and the Dingle temperature TD on Vg and Vs can be obtained. The dependence of m1 on Vg for different values of Vs is compared with the prediction of theory. 相似文献
7.
Actions of negative bias temperature instability (NBTI) and hot carriers in ultra-deep submicron p-channel metal——oxide——semiconductor field-effect transistors (PMOSFETs) 下载免费PDF全文
Hot carrier injection (HCI) at high temperatures and different
values of gate bias Vg has been performed in order to study
the actions of negative bias temperature instability (NBTI) and hot
carriers. Hot-carrier-stress-induced damage at Vg=Vd, where Vd is the voltage of the transistor drain,
increases as temperature rises, contrary to conventional hot carrier
behaviour, which is identified as being related to the NBTI. A
comparison between the actions of NBTI and hot carriers at low and
high gate voltages shows that the damage behaviours are quite
different: the low gate voltage stress results in an increase in
transconductance, while the NBTI-dominated high gate voltage and
high temperature stress causes a decrease in transconductance. It is
concluded that this can be a major source of hot carrier damage at
elevated temperatures and high gate voltage stressing of p-channel
metal--oxide--semiconductor field-effect transistors (PMOSFETs). We
demonstrate a novel mode of NBTI-enhanced hot carrier degradation in
PMOSFETs. A novel method to decouple the actions of NBTI from that
of hot carriers is also presented. 相似文献
8.
N.M. Shash F.E. Salman M.K. El-Mansy H.A. Ghodair 《Journal of Physics and Chemistry of Solids》2004,65(5):891-900
Characterization of the (76V2O5-24P2O5)1−X (Li3PO5)X, where X=0.0,0.01,0.02,0.10 and 0.15, glass has been done using X-ray diffraction and differential thermal analysis (DTA). The dc conductivity of the glass samples was studied over a temperature range from 300 to 593 K. The temperature dependence of dc conductivity shows two regions. One at relatively high temperature range, above θD/2, and the other at relatively low temperature range, below θD/2. The I-V characteristics of the glasses have been studied as a function of both temperature and Li3PO4 content. The I-V characteristics exhibits threshold switching with differential negative resistance. It's found that both the threshold voltage (Vth) and threshold current (Ith) are dependent on the temperature and lithium phosphate concentration. 相似文献
9.
M. Fadel A. Negem H. Metwally M. A. Afifi 《Applied Physics A: Materials Science & Processing》1992,54(3):288-292
Films of the composition Ge40S60 have been studied in the temperature range of 313–423 K for electrical conductivity, and 293–373 K for thermal conductivity. The dc conductivity results indicate a single value activation energy of 0.863 eV for the conductivity in the applied temperature range. The thermal conductivity coefficient increases linearly with temperature at a thickness of d=0.311 cm. It was found that the investigated samples show a memory effect. The threshold switching voltage was found to increase linearly with film thickness. Moreover, the threshold voltage decreases exponentially with temperature. The data are analysed using a thermal model for the switching process. 相似文献
10.
I. G. Gorlova V. Ya. Pokrovskii S. G. Zybtsev A. N. Titov V. N. Timofeev 《Journal of Experimental and Theoretical Physics》2010,111(2):298-303
The structure and transport properties of single crystal whiskers of the TiS3 quasi-one-dimensional semiconductor have been investigated. The anisotropy of the conductivity in the plane of layers (ab) has been measured as a function of the temperature. The anisotropy at 300 K is 5 and increases with a decrease in the temperature.
Features on the temperature dependences of the conductivity along and across the chains are observed at 59 and 17 K. Near
the same temperatures the form of the current-voltage characteristics measured along the chains is qualitatively changed.
The current-voltage characteristics below 60 K exhibit nonlinearity and have a threshold form below 10 K. The results indicate
possible phase transitions and the collective conduction mechanism at low temperatures. 相似文献
11.
V. A. Kulbachinskii V. G. Kytin P. M. Tarasov N. A. Yuzeeva 《Physics of the Solid State》2010,52(9):1830-1835
The effect of Ga doping on the temperature dependences (5 K ≤ T ≤ 300 K) of the Seebeck coefficient α, electrical conductivity σ, thermal conductivity coefficient κ, and thermoelectric
figure of merit Z of p-(Bi0.5Sb0.5)2Te3 single crystals has been investigated. It has been shown that, upon Ga doping, the hole concentration decreases, the Seebeck
coefficient increases, the electrical conductivity decreases, and the thermoelectric figure of merit increases. The observed
variations in the Seebeck coefficient cannot be completely explained by the decrease in the hole concentration and indicate
a noticeable variation in the density of states due to the Ga doping. 相似文献
12.
The ac conductivity (σac) and dielectric permittivity (?) are determined in the temperature range 300?K?T520?K at some selected frequencies (0.5–10?kHz) for the polycrystalline samples of KIO3 compound. The results indicated that the compound behaves as an improper ferroelectric and undergoes a ferroelectric phase transition from a high temperature rhombohedral phase I to a low temperature monoclinic phase II at T c?=?(486?±?1)?K. A second structural phase transition was observed around 345?K. The conductivity varies with temperature range and for T?>?428?K intrinsic conduction prevails. Different activation energies in the different temperature regions were calculated. The frequency dependence of σ(ω) was found to follow the universal dynamic response [σ(ω)∝(ω) s(T)]. The thermal behaviour of the frequency exponent s(T) suggests the hopping over the barrier model rather than the quantum mechanical tunneling model for the conduction mechanism. 相似文献
13.
14.
ABSTRACTExplicit analytical expressions are presented for the density derivative, ?gHS(R; ρ)/?ρ, of the Percus–Yevick approximation to the hard-sphere radial distribution function for R ≤ 6σ, where σ is the hard-sphere diameter and ρ = (N/V)σ3 is the reduced density, where N is the number of particles and V is the volume. A FORTRAN program is provided for the implementation of these for R ≤ 6σ, which includes code for the calculation of gHS(R; ρ) itself over this range. We also present and incorporate within the program code convenient analytical expressions for the numerical extrapolation of both quantities past R = 6σ. Our expressions are numerically tested against exact results. 相似文献
15.
The electrical conductivity, magnetization, and magnetoresistance of manganites La1 − x
Ag
x
MnO3 have been investigated in the temperature range 78–300 K. The samples have been synthesized by the sol-gel method. At room
temperature, the magnetic field of 0.6 T has no effect on the electrical conductivity. As the temperature decreases, an abrupt
jump is observed in the magnetization curve due to the semiconductor-metal phase transition. This transition hardly affects
the temperature dependence of the resistance. 相似文献
16.
Li2xMn1-xPS3 films have been synthesized by exfoliating MnPS3 through the successive intercalations of K+ and Li+ ions. Their dielectric response has been measured from 80 to 350 K in the frequency range of (102–106) Hz. The obtained data have been analyzed in terms of both complex permittivity ε* and the ac conductivity σac. The frequency dependence of σac has been interpreted in terms of the Jonscher’s law, whose exponent n decreases by increasing temperature. The n values lie between 0.479 and 0.501 and are typical of materials in which the ac conductivity is due to multiple hops of carriers. By analyzing the σdc temperature dependence, the observed dielectric response has been attributed to the intercalated lithium ions, and the Li2xMn1-xPS3 films have been classified as hopping charge carrier systems. 相似文献
17.
F.E. SalmanN. Shash H. Abou El-HadedM.K. El-Mansy 《Journal of Physics and Chemistry of Solids》2002,63(11):1957-1966
AC conductivity and dielectric studies on vanadium phosphate glasses doped with lithium have been carried out in the frequency range 0.2-100 kHz and temperature range 290-493 K. The frequency dependence of the conductivity at higher frequencies in glasses obeys a power relationship, σac=Aωs. The obtained values of the power s lie in the range 0.5≤s≤1 for both undoped and doped with low lithium content which confirms the electron hopping between V4+ and V5+ ions. For doped glasses with high lithium content, the values of s≤0.5 which confirm the domination of ionic conductivity. The study of frequency dependence of both dielectric constant and dielectric loss showed a decrease with increasing frequency while they increase with increasing temperature. The results have been explained on the basis of frequency assistance of electron hopping besides the ionic polarization of the glasses. The bulk conductivity increases with increasing temperature whereas decreases with increasing lithium content which means a reduction of the V5+. 相似文献
18.
In this work, a novel compound Bis(2-chloropropyl-N,N-dimethyl-1-ammonium) hexachloridostannate(IV) was synthesized and characterized by; single X-ray diffraction, Hirshfeld surface analysis, differential scanning calorimetric and dielectric measurement. The crystal structure refinement at room temperature reveled that this later belongs to the monoclinic compound with P21/n space group with the following unit cell parameters a = 7.2894(7) Å, b = 12.9351(12) Å, c = 12.2302(13) Å and β = 93.423 (6) °. The structure consists of isolated (SnCl6)2? octahedral anions connected together into layers via hydrogen bonds N–H….Cl between the chlorine atoms of the anions and the hydrogen atoms of the NH groups of the [C5H13NCl]+ cations. Hirschfeld surface analysis has been performed to gain insight into the behavior of these interactions. The differential scanning calorimetry spectrum discloses phase transitions at 367 and 376.7 K. The electrical properties of this compound have been measured in the temperature range 300–420 K and the frequency range 209 Hz–5 MHz. The Cole–Cole (Z′ versus Z″) plots are well fitted to an equivalent circuit model. The transition phase observed in the calorimetric study is confirmed by the change as function of temperature of electrical parameter such as the conductivity of grain (σg) and the σdc. 相似文献
19.
Summary The fluorescence spectra of MnPS3 single crystals have been investigated at various temperatures beginning from 300K down to 10K in the 1.5 eV to 3.0 eV range.
Four structures are observed in all spectra. The strong similarity between these results and previous data concerning the
MnPS3 room temperature fluorescence suggests an intra-Mn nature for the transitions responsible for the above features. All the
subband gap structures exhibit a temperature shift which can be satisfactorily interpreted by means of the crystal field theory
and the so-called ?transition metal weakly interacting? model. The fine splitting in the originally degenerate {4
E
g,4
A
1g} levels is enhanced as temperature decreases. These results confirm the Mn2+ 3ϕ excited-state energy distribution deduced from the transition metal weakly interacting model.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
20.
High-electric-field-stress-induced degradation of SiN passivated AlGaN/GaN high electron mobility transistors 下载免费PDF全文
AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated by employing SiN passivation, this paper investigates the degradation due to the high-electric-field stress. After the stress, a recoverable degradation has been found, consisting of the decrease of saturation drain current IDsat, maximal transconductance gm, and the positive shift of threshold voltage VTH at high drain-source voltage VDS. The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer. The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEG depletion a little during the high-electric-field stress. After the hot carrier stress with VDS=20 V and VGS=0 V applied to the device for 104 sec, the SiN passivation decreases the stress-induced degradation of IDsat from
36% to 30%. Both on-state and pulse-state stresses produce comparative decrease of IDsat, which shows that although the passivation is effective in suppressing electron trapping in surface states, it does not protect the device from high-electric-field degradation in nature. So passivation in conjunction with other technological solutions like cap layer, prepassivation surface treatments, or field-plate gate to weaken high-electric-field degradation should be adopted. 相似文献