The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

Cover Picture: Contrib. Plasma Phys. 9/2015

Effect of DC bias on the spatio‐temporal distribution of the electron density for L = 25 mm, V_pp = 150 V at p = 10 Pa with V_DC = 0 V. The color scales are given in units of 10⁹ cm^–3. (Figure 2b of the paper by N.Kh. Bastykova et al.)     

Anomalous burn-through of thin foils by high-intensity laser radiation

The paper presents results of experiments performed on the Pico facility in which foils were heated by laser radiation, and anomalously fast burn-through of foils by a structured laser beam was detected. Comparison with two-dimensional calculations has allowed us to suggest a tentative mechanism for the effect under investigation. The targets in the experiments were thin aluminum foils of thickness 3 to 40 μm. The flux density of laser radiation on the target surface varied between 10¹³ and 10¹⁴ W/cm². We detected a strong dependence of the transmitted energy on the foil thickness and the shortening of the transmitted laser pulse. Penetration of laser radiation through foils with thicknesses considerably larger than 3 μm has been observed, although it was stated in earlier publications [V. V. Ivanov, A. K. Knyazev, A. V. Kutsenko, et al., Kratk. Soobshch. Fiz. FIAN No. 7–8, 37 (1997)]; A. é. Bugrov, I. N. Burdonskii, V. V. Gol’tsov et al., Zh. éksp. Teor. Fiz. 111, 903 (1997) [JETP 84, 903 (1997)] that, at the laser radiation parameters used in our experiment, the evaporated layer of the foil could not be thicker than 2 μm. Two-dimensional calculations have allowed us to interpret this effect in terms of local “piercing” of the target at spots on the target surface where the radiation intensity has its peaks. The possibility of reducing these peaks by using a symmetrizing prepulse is discussed in the paper. Zh. éksp. Teor. Fiz. 116, 1287–1299 (October 1999)     

FTIR Spectroelectrochemical Investigation of the trans-[Ru(NO)(dimethylglyoximate)2Cl] Complex: Vibrational Characterization of the NO+/0 and RuIII/II Redox Couples

Abstract

This paper deals with the spectroelectrochemical characterization of the Ru^III/II and N0^+/0 oxidation states of the trans-[Ru(NO)(dmgH)₂Cl] complex (dmgH = dimethylglyoximate ion). The cyclic voltammograms of the complex in acetonitrile solution exhibited a reversible wave at -0.09 V versus SHE, and two less intense waves at 1.19 and 1.41 V. Visible-UV spectra were recorded at -0.4 and 1.5 V, however, the absorption bands collapsed into a single tail, providing little information on the redox states involved. In contrast, in the FTIR measurements at -0.4 V, the v(NO) peak shifted from 1878 to 1855cm^?1, without changing the vibrational peaks of the dmgH ligand, indicating an electrochemical process involving the NO^+/0 redox couple. At 1.5 V, the changes in the vibrational peaks of the NO and dig lagans indicated a redox process associated with the Ru^III/II redox'couple. The existence of an open and a cyclic hydrogen bridged configuration was proposed, in order to explain the occurrence of two electrochemical waves at positive potentials.     

Generation of High-Frequency Oscillations by Electromagnetic Shock Wave at Its Synchronism with Backward Harmonic of Periodic Transmission Line Based on Multilayer Heterostructure

The present paper deals with the possibility of generation of high-frequency oscillations by electromagnetic shock wave traveling in synchronism with backward spacial harmonics (group velocity is opposite to the phase velocity) along the previously suggested quasi-periodic microstrip transmission line with capacitance cross links based on multilayer heterostructure (exhibiting hysteretic C(V) characteristic) [1-4]. Just as at synchronism with the direct harmonics, in the case of backward wave synchronism a direct transformation of a short videopulse into a radiopulse (100 GHz, 5-10 V) is possible. However the generated radiopulse here can be significantly longer.     

Coupling in Fe(2 ML)/V(y ML) and Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) (y ≥ 4) superlattices

Fe(2 ML)/V(y ML) and interleaved Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) superlattice systems with spacer thicknesses, y, (4 ≤ y ≤ 17) were investigated macro-magnetically to estimate the coupling strength and the magnetoresistance in these materials, and particularly in the antiferromagnetically coupled monolayers. The results from the magnetic and magnetoresistive measurements indicate that adding one monolayer of Fe increases the antiferromagnetic coupling and the magnetoresistivity ratio from 0.0075 mJ/m² at 20 K and 2 % at 10 K for Fe(2 ML)/V(y ML), to 0.05 mJ/m² and 2.5 % for Fe(2 ML)/V(y ML)/Fe(3 ML)/V(y ML) at the same temperatures. Both systems exhibit in-plane magnetic and magnetoresistive isotropy, therefore the increase of the conferred physical parameters is attributed mainly to the stresses at the interface as governing mechanisms over the magnetoelastic forces.      

A-188 V 7.2Ω·mm~2,P-channel high voltage device formed on an epitaxy-SIMOX substrate

This paper proposes a new n +-charge island (NCI) P-channel lateral double diffused metal-oxide semiconductor (LDMOS) based on silicon epitaxial separation by implantation oxygen (E-SIMOX) substrate.Higher concentration self-adapted holes resulting from a vertical electric field are located in the spacing of two neighbouring n +-regions on the interface of a buried oxide layer,and therefore the electric field of a dielectric buried layer (E I) is enhanced by these holes effectively,leading to an improved breakdown voltage (BV).The V B and E I of the NCI P-channel LDMOS increase to-188 V and 502.3 V/μm from 75 V and 82.2 V/μm of the conventional P-channel LDMOS with the same thicknesses SOI layer and the buried oxide layer,respectively.The influences of structure parameters on the proposed device characteristics are investigated by simulation.Moreover,compared with the conventional device,the proposed device exhibits low special on-resistance.     

Novel high-voltage power device based on self-adaptive interface charge

This paper presents a novel high-voltage lateral double diffused metal--oxide semiconductor (LDMOS) with self-adaptive interface charge (SAC) layer and its physical model of the vertical interface electric field. The SAC can be self-adaptive to collect high concentration dynamic inversion holes, which effectively enhance the electric field of dielectric buried layer (E_I) and increase breakdown voltage (BV). The BV and E_I of SAC LDMOS increase to 612 V and 600 V/μm from 204 V and 90.7 V/μm of the conventional silicon-on-insulator, respectively. Moreover, enhancement factors of η which present the enhanced ability of interface charge on E_I are defined and analysed.     

Optical properties of the HfO2 ? x N x and TiO2 ? x N x films prepared by ion beam sputtering

Optical characteristics of the HfO_{2 − x} N _x and TiO_{2 − x} N _x films obtained by reactive ion beam sputtering have been investigated by spectral ellipsometry. The chemical composition of the films was determined using X-ray photoelectron spectroscopy. The nitrogen content in the oxynitride films (determined by the N₂/O₂ ratio in the gas mixture during synthesis) reached ≈9 at % for TiO_{2 − x} N _x and ≈ 6 at % for HfO_{2 − x} N _x . It is found that the dispersion relations n(λ) and k(λ) for the TiO_{2 − x} N _x films change from those characteristic of titanium dioxide to those typical of titanium nitride with an increase in the nitrogen content from 0 to ≈9 at %. The optical parameters of the HfO_{2 − x} N _x films depend weakly on the nitrogen content in the range 0–6 at %. Original Russian Text ? V.V. Atuchin, V.N. Kruchinin, A.V. Kalinkin, V.Sh. Aliev, S.V. Rykhlitskiĭ, V.A. Shvets, E.V. Spesivtsev, 2009, published in Optika i Spektroskopiya, 2009, Vol. 106, No. 1, pp. 77–82.     

The analysis of reactions π<Subscript>N</Subscript> → <Emphasis Type="Italic">two mesons</Emphasis> + <Emphasis Type="Italic">N</Emphasis> within reggeon exchanges. Fit and results

We present technical aspects of the fitting procedure given in the paper by V.V. Anisovich and A.V. Sarantsev “The analysis of reactions πN → two mesons + N within reggeon exchanges. Fit and results.”     

Geometrical,electronic, and magnetic properties of Au n V (n = 1–8) clusters: A density functional study

The geometrical, electronic, and magnetic properties of small Au _n V (n?=?1–8) clusters have been investigated using density functional theory at the PW91 level. An extensive structural search indicates that the V atom in low-energy Au _n V isomers tends to occupy the most highly coordinated position and the ground-state configuration of Au _n V clusters favors a planar structure. The substitution of a V atom for an Au atom in the Au _{n +1} cluster transforms the structure of the host cluster. Maximum peaks are observed for the ground-state Au _n V clusters at n?=?2 and 4 for the size dependence of the second-order energy differences, implying that the Au₂V and Au₄V clusters possess relatively higher stability. The energy gap of the Au₃V cluster is the largest of all the clusters. This may be ascribed to its highly symmetrical geometry and closed eight-electron shell. For ground-state clusters with the same spin multiplicity, as the clusters size increases, the vertical ionization potential decreases and the electron affinity increases. Magnetism calculations for the most stable Au _n V clusters demonstrate that the V atom enhances the magnetic moment of the host clusters and carries most of the total magnetic moment.     

Phase transitions in solid solutions (1 ? x)BaTiO3-xBaMg1/3B2/3O3 (B = Nb, Ta)

The dielectric properties of ceramic samples of (1 − x)BaTiO₃-xBaMg_1/3Nb_2/3O₃ and (1 − x)BaTio₃-xBaMg_1/3Ta_2/3O₃ solid solutions (x = 0–0.25) are investigated in the frequency range from 10 Hz to 100 kHz at temperatures of 77–450 K. It is shown that the (x−T) phase diagrams of these solid solutions at x = 0.05 have a multiphase point at which the lines of all three phase transitions of BaTiO₃ converge. Original Russian Text ? V.G. Zalesskiĭ, V.V. Lemanov, E.P. Smirnova, A.V. Sotnikov, N. V. Zaĭtseva, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 1, pp. 108–112.     

A novel high-voltage light punch-through carrier stored trench bipolar transistor with buried p-layer

A novel high-voltage light punch-through(LPT) carrier stored trench bipolar transistor(CSTBT) with buried p-layer(BP) is proposed in this paper.Since the negative charges in the BP layer modulate the bulk electric field distribution,the electric field peaks both at the junction of the p base/n-type carrier stored(N-CS) layer and the corners of the trench gates are reduced,and new electric field peaks appear at the junction of the BP layer/N drift region.As a result,the overall electric field in the N drift region is enhanced and the proposed structure improves the breakdown voltage(BV) significantly compared with the LPT CSTBT.Furthermore,the proposed structure breaks the limitation of the doping concentration of the N-CS layer(NN CS) to the BV,and hence a higher NN CS can be used for the proposed LPT BP-CSTBT structure and a lower on-state voltage drop(Vce(sat)) can be obtained with almost constant BV.The results show that with a BP layer doping concentration of NBP = 7 × 1015 cm-3,a thickness of LBP = 2.5 μm,and a width of WBP = 5 μm,the BV of the proposed LPT BP-CSTBT increases from 1859 V to 1862 V,with NN CS increasing from 5 × 1015 cm-3 to 2.5 × 1016 cm-3.However,with the same N-drift region thickness of 150 μm and NN CS,the BV of the CSTBT decreases from 1598 V to 247 V.Meanwhile,the Vce(sat) of the proposed LPT BP-CSTBT structure decreases from 1.78 V to 1.45 V with NN CS increasing from 5 × 1015 cm-3 to 2.5 × 1016 cm-3.     

Hot carrier injection degradation under dynamic stress

In this paper,we have studied hot carrier injection(HCI) under alternant stress.Under different stress modes,different degradations are obtained from the experiment results.The different alternate stresses can reduce or enhance the HC effect,which mainly depends on the latter condition of the stress cycle.In the stress mode A(DC stress with electron injection),the degradation keeps increasing.In the stress modes B(DC stress and then stress with the smallest gate injection) and C(DC stress and then stress with hole injection under V g = 0 V and V d = 1.8 V),recovery appears in the second stress period.And in the stress mode D(DC stress and then stress with hole injection under V g = 1.8 V and V d = 1.8 V),as the traps filled in by holes can be smaller or greater than the generated interface states,the continued degradation or recovery in different stress periods can be obtained.     

Effects of V/III ratio on the growth of a-plane GaN films

The non-polar a-plane GaN is grown on an r-plane sapphire substrate directly without a buffer layer by metal-organic chemical vapour deposition and the effects of V/III ratio growth conditions are investigated. Atomic force microscopy results show that triangular pits are formed at a relatively high V/III ratio, while a relatively low V/III ratio can enhance the lateral growth rate along the c-axis direction. The higher V/III ratio leads to a high density of pits in comparison with the lower V/III ratio. The surface morphology is improved greatly by using a low V/III ratio of 500 and the roughness mean square of the surface is only 3.9 nm. The high resolution X-ray diffraction characterized crystal structural results show that the rocking curve full width at half maximum along the m axis decreases from 0.757° to 0.720°, while along the c axis increases from 0.220° to 0.251° with the V/III increasing from 500 μmol/min to 2000 μmol/min, which indicates that a relatively low V/III ratio is conducible to the c-axis growth of a-plane GaN.     

Simulation of an electron avalanche in helium

The parameters of an avalanche generated by an electron in helium at different ratios E/p, where E is the external field strength and p is the pressure, are simulated. The E/p dependences of the ionization rate and Townsend coefficient have maxima at E/p≈1000 and ≈200 V/(cm Torr), respectively. The today’s concepts of the electron density distribution in the avalanche are valid only at small values of the reduced strength, E/p<100 V/(cm Torr). With E/p>100 V/(cm Torr), the electron density distribution extends along the field.     

Gravity in one dimension: Diffusion in acceleration

The one-dimensional gravitational system consists ofN parallel sheets of constant mass density. The sheets move perpendicular to their surface solely under their mutual gravitational attraction. When a pair has an encounter, they simply pass through each other. In this paper I consider the motion of a single sheet in an equilibrium ensemble. Under the assumption that the times separating encounters are random, I show that the acceleration and velocity(A, V) of a labeled sheet form a Markovian pair. Further, I prove that, in the limit of largeN, (1)the(A, V) process is deterministic, (2) the(A, V) process obeys Vlasov dynamics, and (3) that scaled fluctuations in(A, V) comprise a diffusion which obeys a generalized Ornstein-Uhlenbeck process with time-dependent drift and diffusion tensors.     

The superconductivity and metallurgy of C15 materials: Hf-V and Zr-V

Variation of theT _c as a function of composition for the C15 materials of the systems Hf−V and Zr−V was investigated. Samples in the as cast and annealed conditions were examined by x-ray and optical metallography. None of the samples was found to be of single phase. For the Hf−V system,T _c increases to a constant value of about 9 K for the compositions between 36 and 60 at. %V. A slight increase ofT _c between 60 and 70 at. %V and a degradation inT _c above 80 at. %V were observed. As cast materials show the maximumT _c value of 9.4 K. Deviations from stoichiometry and heat treatments produce considerable changes in the microstructures but have little effect onT _c . A slight enhancement ofT _c for the alloy containing 80 at. %V is explained by the pressure on V₂Hf due to V phase by the differential thermal contraction. For the Zr−V system, maximumT _c value of 8–6 K was observed for alloys having 20–66 at. %V in as cast condition. Heat treatments cause the lowering ofT _c . Results indicate that the preparation of ZrV₂ superconducting material will need more careful control than would be necessary for HfV₂.     

Q-value for the Fermi beta-decay of <Superscript>46</Superscript>V

By comparing the Q -values for the ⁴⁶Ti ( ³He , t ⁴⁶V and ⁴⁷Ti ( ³He , t ⁴⁷V reactions to the isobaric analogue states the Q -value for the superallowed Fermi decay of ⁴⁶V has been determined as Q _EC( ^46V ) = (7052.11±0.27) keV. The result is compatible with the values from two recent direct mass measurements but is at variance with the previously most precise reaction Q -value. As additional input quantity we have determined the neutron separation energy S _n( ^47Ti ) = (8880.51±0.25) keV.     

Current transport in ZnO/Si heterostructure grown by laser molecular beam epitaxy

The n-ZnO/p-Si heterojunction was fabricated by depositing high quality single crystalline aluminium-doped n-type ZnO film on p-type Si using the laser molecular beam epitaxy technique. The heterojunction exhibited a good rectifying behavior. The electrical properties of the heterojunction were investigated by means of temperature dependence current density-voltage measurements. The mechanism of the current transport was proposed based on the band structure of the heterojunction. When the applied bias V is lower than 0.15 V, the current follows the Ohmic behavior. When 0.15V 0.6 V), the space charge limited effect becomes the main transport mechanism. The current-voltage characteristic under illumination was also investigated. The photovoltage and the short circuit current density of the heterojunction aproached 270 mV and 2.10 mA/cm 2 , respectively.