摘要:

The growth striation, resistance homogeneity, and oxygen concentration of silicon single crystal grown by both magnetic Czochralski and Czochralski methods were investigated. Theoretical analysis of the experimental results, including effect of magnetic field on the temperature fluctuation, effective segregation coefficient (keff), and oxygen concentration are discussed.

ISSN:0021-8979    

DOI:10.1063/1.346760

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Temperature profiles were calculated numerically for a three‐layer stack of SiO2‐Si‐SiO2on top of a monocrystalline Si substrate. The stack was locally heated by a CO2laser whereas the wafer background temperature was controlled by a heat chuck. The calculation method makes it possible to simulate temperatures as functions of laser power, spot radius, scan speed, substrate bias temperature, and layer thickness. These parameters play a major role in CO2laser recrystallization of polycrystalline silicon for making single crystalline silicon films on insulator films. It is shown that under conditions of maximum absorption experimental verification of the calculations is possible by measuring the recrystallized track width. A good agreement was found between the calculated and measured results.

ISSN:0021-8979    

DOI:10.1063/1.346761

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Photochemical (PC) etching ofn‐InP using an Ar+laser and dilute phosphoric acid solutions was studied as a function of temperature, power, illumination frequency, and duty cycle. The etch rate was found to be independent of time and to increase fourfold by increasing temperature from 20 to 50 °C with an activation energy ≳0.34 eV. Thus the process is found to be reaction rate limited. The etch rate was observed to increase with power for low‐power levels and then saturate near an irradiance of 200 W/cm2at 20 °C. The photoetch rate, i.e., the etch rate divided by the fraction of time the Ar+light is on, was affected by illumination duty cycle but not chopping frequency in the range 100–3200 Hz. These results are explained based on a rate equation model for material removal. Finally, a new application for PC etching is presented: sample preparation for transmission electron microscopy.

ISSN:0021-8979    

DOI:10.1063/1.347183

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experiments have been completed on electrostatic and electromagnetic phase locking of two independent virtual cathode oscillators (VCO). The experiments were accomplished by using the Gemini electron beam accelerator. The Gemini accelerator was used to generate each VCO with a chosen time separation. The phase locking was observed by beating microwave signals generated in each anode‐cathode gap and noting the time intervals during which the phase difference remained constant. The phase locking was observed during both electrostatic and electromagnetic coupling of the microwave power between the VCOs. We did find that one must prefill the coupling cavity with microwave power to enable one VCO to phase lock the other.

ISSN:0021-8979    

DOI:10.1063/1.346762

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

InGaAs(P)/InP double heterojunction bipolar transistors have been successfully fabricated by inserting ann‐type InGaAsP (Eg=0.95 eV) quaternary (0.1 &mgr;m, undoped) layer on either side of the base by liquid‐phase epitaxy (LPE). As we know, it is the first time to grow this structure by LPE. These devices have been fabricated using a non‐self‐aligned technology. In this case it can improve the common‐emitter current/voltage (IC /VCE) characteristics. Small signal current gainhfeabout 100 and dc current gainhFEabout 80 atIC=38 mA can be obtained. The ideality factor of emitter‐base junction is 1.43.

ISSN:0021-8979    

DOI:10.1063/1.346763

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using substrates from different composition liquid‐encapsulated Czochralski‐grown crystal boules, the 1.5 &mgr;m×400‐&mgr;m wide‐gate metal‐semiconductor field‐effect‐transistors (MESFETs) drain current (Id)‐drain voltage (Vd) characteristic at near pinch‐off bias was observed as a low‐frequency oscillation (LFO)Id‐Vdcurve. This process indicates the interfacial behavior of the MESFET’sIdbetween GaAs crystal bulk and the Si‐implanted electrically active channel layer. As a result, both the LFO behavior and theId‐Vdcurve at the interfacial layer were dependent on the substrate GaAs composition but were not dependent on its impurity boron concentration. LargeId‐LFO was observed for the substrates from near‐ or stoichiometric GaAs melts and compared with theId‐LFO for As‐rich melts. With the As‐rich melt samples, smallId‐LFO was observed for both low carbon concentration (nondetectable) and high carbon concentration (&bartil;2×1016cm−3) in the substrates. From the result and discussion of the LFO model,Id‐LFO is not caused by the deep center but by the interaction among both the electron carrier (in this case), and the deep center and electrical potential profile. This is formed by imposed electric bias force and nonbias potential profile of both the electrically active impurity doping profile of process and the mixed band structure of substrate bulk, and occurs because theId‐LFO is small on an As‐rich substrate which can have many native deep‐center EL2s.

ISSN:0021-8979    

DOI:10.1063/1.346764

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The physical properties of a coaxial saturable inductor magnetic switch have been examined as a stand‐alone unit and as a component in a pulse forming circuit. A methodology for optimizing the performance of this type of switch for which voltage holdoff and saturated inductance are specified is presented. It is shown that the volume and hence cost of the switch can be reduced by 20% with an appropriate choice of switch dimensions. Additional cost reduction may be achieved by a considered choice of core material. It is also shown that, for a single‐stage compression circuit with compression less than 10, further significant cost reduction can be achieved by designing the switch to close at a fraction of the theoretical maximum holdoff voltage and by choosing the switch saturated inductance appropriately.

ISSN:0021-8979    

DOI:10.1063/1.346765

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The ZnO varistor is known to require a postsintering heat treatment (annealing) to impart stability to an otherwise unstable device, when subjected to an applied voltage stress. A large body of experimental data in the literature indicate that the most desirable temperature of annealing isbetween600 and 700 °C at which the varistor becomes highly stable. This paper is aimed at understanding the significance of this annealing temperature from the analysis of the activation energies, estimated from the Arrhenius plots of the resistive current versus temperature in the prebreakdown region. It is found that the activation energy in the annealing temperature range of 600–700 °C is significantly higher than at any other annealing temperature between 500 and 800 °C. This conclusion is borne out by the statistical evaluation of the experimental data. When this result is combined with the equally notable observations in the literature that the interface state density [J. Mater. Sci.20, 3487 (1985)], the grain‐boundary trap density [J. Appl. Phys.63, 5375 (1988)], and the density of the negatively charged zinc vacancy at the interface [J. Appl. Phys.66, 6132 (1989)] are all reduced, also at the same annealing temperature range, it becomes clear that the annealing temperature of 600–700 °C is very unique to varistor stability. The significance of these observations is that the annealing and accompanying stability should be recognized as a very complex process that brings fundamental changes in the grain‐boundary junction characteristic of the polycrystalline ceramic.

ISSN:0021-8979    

DOI:10.1063/1.346766

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Following an earlier study on the temperature dependence of the resistive component of the leakage current of a ZnO varistor, a detailed study has been undertaken in this paper to compare the temperature dependence of the resistive (IR), capacitive (IC), and total (IT) leakage currents between unannealed and 600 °C annealed samples. It is shown that, as before, an Arrhenius plot ofICandIRversus temperature can best be represented by a break in the plot comprising a high‐temperature regime (125–165°C) with a high activation energy and a low‐temperature regime (30–100 °C with a low activation energy. The activation energies ofIR‐Tcurves are generally higher than those ofIC‐Tcurves in both temperatures regimes. Upon annealing at the critical temperature of 600 °C, the activation energy changes for both current components, accompanied by increased stability of the varistor. ForIR, the activation energy becomes higher in the low‐temperature regime in agreement with previous observation, and forIC, it becomes lower in the higher‐temperature regime. The relative contributions of these two current components on total current are also different in the two temperature regimes. In the low‐temperature regime, the total current is mostly capacitive, and in the high‐temperature regime, it is mostly resistive. The varistor is thus prone to more Joule heating in the high‐temperature regime than in the low‐temperature regime.

ISSN:0021-8979    

DOI:10.1063/1.346767

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report the effect of silver addition on the surface quality of rf‐sputtered Y‐Ba‐Cu‐O thin films. The Y‐Ba‐Cu‐O‐Ag films appear to have very smooth surfaces even if the post‐annealing step is employed. The surface roughness of ourexsitugrown Y‐Ba‐Cu‐O‐Ag film, having a 10.3 wt. % of silver, is within ±1% of the film thickness, which is more than 10 times better than the value of a typical post‐annealed high‐temperature superconducting film without silver.

ISSN:0021-8979    

DOI:10.1063/1.346768

出版商:AIP    

年代:1990

数据来源: AIP