Static and switching characteristics of field-controlled integrated thyristor

The static parameters of and switching transients in an advanced high-voltage high-speed switching device—a MOSFET-controlled integrated thyristor—and their dependences on the geometry and electrophysical properties of base layers in the n ⁺ pnn’p ⁺ device structure are studied experimentally. It is shown that the residual resistance of the high-voltage (∼2.5 kV) microthyristor chip in the on-state is much smaller than that of the high-voltage IGBT with the speed of the former kept at a sufficiently high level. The new device is multifunctional and can operate under different operating conditions. Specifically, it can be turned off by shunting the n ⁺ p emitter by an add-on MOSFET, by applying a gate current pulse, and in the cascode turn-off regime. In these regimes, the ultimate value of the turn-off current noticeably grows.     

Cascode turn-off of field-controlled integrated thyristors

The residual voltage drop in the on state of an insulated-gate bipolar transistor, the basic device of today’s power electronics, is considerably higher than that of conventional thyristor-type devices, which is a serious disadvantage of the former. Field-controlled integrated thyristors offering a low residual voltage, as with conventional thyristors, and, at the same time, low turn-on and turn-off power losses in the control circuit, as is the case with insulated-gate bipolar transistors, seem to be promising for high-voltage high-power applications. Turn-off of these devices in the cascode mode with a series-connected low-voltage powerful FET is studied.     

Distributed microgate bipolar switches: Onset conditions for dynamic breakdown at turn-off

A versatile compact technique for calculating dynamic avalanche breakdown conditions in the case of p ⁺ nn ₀(p ₀)pn ⁺ bipolar structures with distributed microgates cut off in a resistively loaded circuit is suggested. These conditions determine the breakdown-limited ultimate switching power of a specific device. Examples of calculating the current, voltage, and power boundaries of the safe operating area for Si- and 4H-SiC-based structures are given. It is found that structures with gates extracting minority carriers having a higher impact ionization coefficient (electrons from the p ₀-base for silicon or holes from the n ₀-base for 4H-SiC) are most prone to breakdown. On the contrary, structures with gates of the opposite type, i.e., those extracting holes from the p ₀-base for Si or electrons from the n ₀-base for 4H-SiC (such structures have not yet found wide application), are most stable against breakdown. It is found that implementation of such structures for Si switches with switching voltage U _max= 5–7 kV may raise the maximal power per unit area from today’s ～200 kW/cm² to a new theoretical level of 0.7–1.0 MW/cm². For 4H-SiC switches with U _max = 4.5–10.0 kV, a new level can be increased to 200 MW/cm² or higher.     

Electronic spectra and structure of the hydrogen halides: Characterization of the electronic structure of DI lying between 67 800 and 74 400 cm−1 above X1Σ+

High-resolution absorption spectra of DI were reinvestigated in the 1475-Å (67 800 cm^?1) to 1344-Å (74 400 cm^?1) region. This spectral region was found to contain bands attributable to (1) V¹Σ⁺-X¹Σ⁺(v′-0) with v′ > 0, (2) (v′-0) transitions with v′ ≥ 0 from X¹Σ⁺ to states associated with the (σ²π³)cπ and (σ²π³)cσ configurations, and (3) (v′-0) transitions with v′ ≥ 0 from X¹Σ⁺ to states associated with the previously unreported configurations (σ²π³)dσ, dπ, aδ, eσ, and fσ.     

Electronic spectra and structure of the hydrogen halides: Characterization of the electronic structure of HI lying between 67 800 and 74 400 cm−1 above X1Σ+

High-resolution absorption spectra of HI were reinvestigated in the 1475-Å (67 800 cm^?1) to 1344-Å (74 400 cm^?1) region. This spectral region was found to contain bands attributable to (1) V¹Σ⁺-X¹Σ⁺(v′-0) with v′ > 0, (2) (v′-0) transitions with v′ ≥ 0 from X¹Σ⁺ to states associated with the (σ²π³)cπ and (σ²π³)cσ configurations, and (3) (v′-0) transitions with v′ ≥ 0 from X¹Σ⁺ to states associated with the previously unreported configurations (σ²π³)dσ, dπ, aδ, eσ, and fσ.     

Electrical properties of p +/n + InGaAsP tunnel diodes with a bandgap of 0.95 eV grown by liquid phase epitaxy

p ⁺/n ⁺ InGaAsP tunnel diodes with a bandgap of 0.95 eV were fabricated by liquid phase epitaxy and their electrical properties were characterized. Forward conductances of 500 ^–1 cm^–2, peak current densities of 28.5 A/cm² and peak to valley current ratios of 14.3 were obtained at room temperature. These devices were incorporated successfully as Intercell Ohmic Connections (IOCs) for an InP-based, two-terminal monolithic multijunction tandem solar cell.     

Electrical properties of p +/n + In0.53Ga0.47As tunnel diodes grown by liquid phase epitaxy

p ⁺/n ⁺ In_0.53Ga_0.47As tunnel diodes were prepared by liquid phase epitaxy and their electrical properties were characterized. These devices exhibit large forward conductances (2.59×10^{3 –1} cm^–2), high peak current densities (793 A/cm²) and large peak to valley current ratios (16.2). These devices offer great promise as intercell ohmic contacts (IOCs) for InP-based, onolithic multijunction solar cells.     

镓铝双质掺杂在制造快速晶闸管中的应用研究

采用开管式Al乳胶源涂布与气相Ga相结合的技术,实现了镓铝双质在n型Si中的均匀掺杂,得到了p型半导体.研究了镓铝双质掺杂的方法及其与器件性能的关系,并讨论了机理.利用扩展电阻法、四探针和晶闸管测试仪等手段,测试了镓铝扩散Si片的杂质分布规律、薄层电阻R_S及快速晶闸管的多项参数.利用该技术制造的快速晶闸管的关断时间t_off为31.2—38.6 μs,开通时间t_on为4.6—5.9 μs,通态峰值压降 关键词： 快速晶闸管 镓铝双质掺杂技术 杂质浓度分布     

n,p柱宽度对超结SiGe功率二极管电学特性的影响

结合SiGe材料的优异性能与超结结构在功率器件方面的优势,提出了一种超结SiGe功率二极管.该器件有两个重要特点:一是由轻掺杂的p型柱和n型柱相互交替形成超结结构,取代传统功率二极管的n^-基区;二是阳极p⁺区采用很薄的应变SiGe材料.该二极管可以克服常规Si p⁺n^-n⁺功率二极管存在的一些缺陷,如阻断电压增大的同时,正向导通压降随之增大,反向恢复时间也变长.利用二维器件模拟软件MEDICI仿真 关键词： 超结 锗硅二极管 n p柱宽度 电学特性     

Studies of labile molecules with a tunable dye laser: Laser excitation spectrum of BrF (B3Π(0+)-X1Σ+)

The B³Π(0⁺) ← X¹Σ⁺ absorption spectrum of BrF (4850–5200 Å) has been observed by the technique of laser emission spectroscopy. Fluorescence was excited by a pulsed, scannable dye laser with a 0.1 Å bandwidth. Rotational analysis has been carried out for six bands of the v″ = 0 progression (8 ≥ v′ ≥ 3) of ⁷⁹BrF and ⁸¹BrF. Rotational constants for the B³Π(0⁺) state are reported for the first time. RKR potential energy curves for both states, and an array of Franck-Condon factors and r-centroids for the transition, have been calculated. Bands with v′ > 8 were not observed in fluorescence owing to the onset of predissociation near J′ = 28 of the v′ = 8 level. An upper limit for the ground state dissociation energy is D₀″ (BrF, X¹Σ⁺) ≤ 20 880 cm^?1.     

A super junction SiGe low-loss fast switching power diode

This paper proposes a novel super junction (SJ) SiGe switching power diode which has a columnar structure of alternating p^- and n^- doped pillar substituting conventional n^- base region and has far thinner strained SiGe p⁺ layer to overcome the drawbacks of existing Si switching power diode. The SJ SiGe diode can achieve low specific on-resistance, high breakdown voltages and fast switching speed. The results indicate that the forward voltage drop of SJ SiGe diode is much lower than that of conventional Si power diode when the operating current densities do not exceed 1000 A/cm², which is very good for getting lower operating loss. The forward voltage drop of the Si diode is 0.66V whereas that of the SJ SiGe diode is only 0.52 V at operating current density of 10 A/cm². The breakdown voltages are 203 V for the former and 235 V for the latter. Compared with the conventional Si power diode, the reverse recovery time of SJ SiGe diode with 20 per cent Ge content is shortened by above a half and the peak reverse current is reduced by over 15%. The SJ SiGe diode can remarkably improve the characteristics of power diode by combining the merits of both SJ structure and SiGe material.     

Nuclear structure of low-lying 0+ states in Ge and Se isotopes

The following meanlives of levels in⁷²Se have been measured using the recoildistance Doppler-shift method:Τ(2⁺, 862 keV)=3.1±0.6 ps,Τ(2⁺′, 1317 keV)=12.5±2.6 ps,Τ(4⁺, 1638 keV)=1.2±0.3 ps andΤ(6⁺, 2469 keV)≦0.7 ps. These meanlives yield sixB(E2) values which are discussed together with the known data of the depopulation of the excited 0⁺′ state at 937 keV. Systematics of 0⁺′ states in the mass region 70?A?100 show that the low excitation energy of the 0⁺′ states is correlated with subshell closures. This suggests that the previous interpretation of the 0⁺′ state in⁷²Se as a rotational band head is questionable.     

Electronic spectra and structure of the hydrogen halides: Characterization of the electronic structures of HBr and DBr lying between 79 500 and 83 900 cm−1 above X1Σ+

The high-resolution absorption spectra of HBr and DBr were reinvestigated in the 1258-Å (79 500 cm^?1) to 1192-Å (83 900 cm^?1) region. This spectral region was found to contain bands attributable to (1) V¹Σ⁺-X¹Σ⁺(v′ - 0) with v′ > 0, (2) (v′ - 0) transitions with v′ > 0 from X¹Σ⁺(v″ = 0) to states associated with the (σ²π³)cπ and (σ²π³)cσ configurations, and (3) (v′ - 0) transitions with $\text{v′ ≧ 0}$ from X¹Σ⁺(v″ = 0) to states associated with the previously unreported configurations (σ²π³)dσ, dπ, aδ, eσ, and fσ.     

Characteristics of a photovoltaic X-ray detector based on a GaAs epitaxial structure

The characteristics of a photovoltaic X-ray detector based on the GaAs p ⁺-n-n′-n ⁺ epitaxial structure grown using gas-phase epitaxy are studied. Typical current-voltage and capacitance-voltage characteristics of the epitaxial structures are analyzed together with the built-in electric field profile in the n-GaAs depleted region. The efficiency of charge accumulation in the photovoltaic detector is measured for zero bias and for a bias voltage of 17 V. It is shown that the GaAs-based photovoltaic X-ray detector can operate with zero bias voltage at room temperature. The sensitivity of the detector is measured as a function of the effective energy of X-rays and the angle of incidence of X-ray photons.     

High power photoconductive switches of 4H SiC with Si3N4 passivation and n -GaN subcontact

The effect of a Si₃N₄ passivation layer on the breakdown voltage in 4H SiC high power photoconductive semiconductor switching devices has been investigated. An n⁺-GaN epitaxial layer was also used for these devices as a subcontact layer, which was between the contact metal and the high resistivity SiC bulk, to improve the ohmic contact and mitigate current spreading: the GaN subcontact layer protects the contact from damage occurring at high power levels. The Si₃N₄ passivation layer was grown by ultrahigh vacuum plasma enhanced chemical vapor deposition. By using the Si₃N₄ passivation, the dark leakage current of the devices was suppressed effectively and decreased by one order of magnitude, and the breakdown voltage of the switching devices was improved significantly from 2.9 to 5 kV without degrading the high photocurrent.     

Excitation energy transfer in dye-doped ternary polymer blends for light-emitting diodes and lasers

We present the organic electroluminescent devices and lasers of which the colors are tuned by utilizing the Förster excitation energy transfer. Fluorene-based light emitting polymers, poly(2,7-bis(p-stiryl)-9,9^′-di-n-hexylfluorene sebacate) (PBSDHFS), poly(9,9^′-di-n-hexyl fluorenediylvinylene-alt-1,4-phenylenevinylene) (PDHFPPV), and a laser dye, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) were used as the components of the energy transfer systems. Color-tunable photoluminescence, electroluminescence, and laser emission in the PBSDHFS/PDHFPPV binary and PBSDHFS/PDHFPPV/DCM ternary blends are demonstrated.     

Laser-induced fluorescence and microwave-optical double-resonance study of the B1Σ+-X1Σ+ system of magnesium monoxide

Doppler-limited, laser-induced fluorescence spectra on the B¹Σ⁺-X¹Σ⁺ (v′ = v″ = 0 and 1) system of MgO have been obtained. The results of the optical analysis were merged with our microwave-optical double-resonance measurements to produce the following set of spectroscopic parameters for the B and X states, where the units are in cm^?1, and the uncertainties represent 95% confidence limits: T′_0.0 = 20003.594(2); B′₀ = 0.58004(3); D′₀ = 1.13(2) × 10^?6; B″₀ = 0.57198(3); D″₀ = 1.20(2) × 10⁶; T′_1.1 = 20043.423(2); B′₁ = 0.57528(4); D′₁ = 1.14(11) × 10⁶; B″₁ = 0.56674(4); D″₁ = 1.22(10) × 10⁶.     

Extension of the rotational analysis of the 1Π-X1Σ+ system of AsN

Rotational analysis of bands with v′ = 0 through 3, in the ¹Π-X¹Σ⁺ system as the AsN molecule, has been carried out. Rotational constants for the X¹Σ⁺ state are: B_e = 0.54551 cm^?1, α_e = 0.003366 cm^?1 and D_e = 5.3 × 10^?7cm^?1. Strong perturbations are observed in the upper levels and the resulting B_v curves are plotted against J.     

Torsion-rotation levels of the OH stretch fundamental of CD3OH

The infrared absorption of CD₃OH in the OH stretch region has been observed at 0.025-cm^?1 resolution. Seventeen excited-state torsion-rotation levels E′_nτK have been determined with the aid of combination differences and Loomis-Wood diagrams. Of these levels, seven belong to n = 2 and nine to n = 1. No levels for which n = 0 could be determined. Analysis of the observed levels yields a hindering potential barrier in the excited state of 407 cm^?1.     

High-efficiency organic light-emitting diodes (OLEDs) with a mixed layer structure

Improved performance of organic light-emitting diodes (OLEDs) as obtained by a mixed layer was investigated. The OLEDs with a mixed layer which were composed of N,N′-diphenyl-N,N′-bis(1-napthyl-phenyl)-1,1′-biphenyl-4,4′-diamine (NPB), tris-(8-hydroxyquinolato) aluminum (Alq₃) and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) showed the highest brightness and efficiency, which reached 19048 cd/m² at 17 V and 4.3 cd/A at 10 mA/cm², respectively. The turn-on voltage of the device is 2.6 V. Its Commission Internationale del’Eclairage (CIE) coordinate is (0.497, 0.456) at 17 V, and the CIE coordinates of the device are largely insensitive to the driving voltages, which depicts stabilized yellow color.