摘要:

In very large‐scale integration, the trend towards smaller horizontal dimensions and shallower doping profiles within NPN bipolar devices aggravates degradation mechanisms affecting common‐emitter current gain (beta). It is experimentally shown for shallow junction NPN bipolar transistors operating in the conduction mode that the degradation of beta is electromigration related. Increasing the passivation thickness simultaneously improves metal conductor lifetime and aggravates beta degradation. Both increases are attributed to the electromigration‐induced compressive stress. The complete recovery of beta after a 400 °C anneal indicates that the electromigration‐induced compressive stress is relieved by creep in an aluminum‐based metallization. The experimental results for beta degradation are consistent with an existing theory that takes into account the effects of stress on the effective mass of light and heavy holes.

ISSN:0021-8979    

DOI:10.1063/1.331231

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

In a new display cell, a holding voltage compresses the regions where the director is not essentially vertical into thin boundary layers adjacent to the surfaces. With opposite surfaces tilt biased in opposite senses, and with suitable isolation regions, the director field contains a horizontal director line. Above a certain threshold voltage the stable states are asymmetric, with the horizontal director line nearer one surface than the other. In a twist cell, thesebistablestates can be discriminated optically with either a dichroic dye and a single polarizer or with two polarizers using birefringence effects. A dye gives poor results because the horizontal absorbing layers are thin. However, the birefringence effects enable good contrast to be obtained. We examine the brightness and contrast by studying the transmission of monochromatic light passing normally through the cell in the two states. We include an analysis of polarized light propagating through two birefringent layers of arbitrary phase difference, and whose principal planes are at arbitrary angles to each other and to the polarizers. A separate analysis relates the phase difference of the layers to the voltage and cell boundary conditions. In order to determine suitable operating conditions with two polarizers, we carry out several different calculations. These include: (1) calculating, with one state totally extinguished, the transmission of the other state when the cell twist is 45° and when the cell twist is adjusted to maximize that transmission; (2) calculating the transmission and contrast ratio under conditions that maximize the transmission difference of the two states; and (3) calculating the contrast ratio when the polarizer and cell twist are set to make the brighter state give circular polarization (in order to minimize chromatic effects). A qualitative experimental confirmation is included.

ISSN:0021-8979    

DOI:10.1063/1.331232

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Thermal annealing of damage‐induced strain in ion‐implanted epitaxial garnet films has been studied. The high strains typical of ion‐implanted propagation patterns decrease nearly linearly with the logarithm of annealing time (ln t), a functional dependence characteristic of thermally activated processes with a broad spectrum of activation energies. The theory of Vand, as extended by Primak, satisfactorily describes the data. In as‐implanted material, significant relaxation of the implantation strain is predicted for a device operating at 125 °C for several years. However, a stabilizing anneal for 30 min at 325–350 °C is adequate to assure 99% stability for 20 years at 125 °C. The required anneal is consistent with current design and fabrication practices.

ISSN:0021-8979    

DOI:10.1063/1.331233

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

For a magneto‐optical readout system which uses the Kerr effect, the power spectral density of the read signal has been derived. The noise components originating in the photodetection and amplification stages appear as additive terms in the expression for the overall spectral density, enabling us to define a signal to noise ratio for the readout system. Adjustable parameters of the system are then optimized and a multilayer disk structure is introduced which enhances the Kerr effect and, consequently, results in an increased signal to noise ratio.

ISSN:0021-8979    

DOI:10.1063/1.331185

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The geometry and porosity of dry snow varies widely depending on the history of conditions. The permittivity of dry snow increases with increasing ice content but is not greatly affected by the shapes of the ice particles. In wet snow the permittivity increases with liquid content and the geometry is very important. However, the liquidlike layer has little effect on permittivity. The permittivity is described using Polder and van Santen’s mixing formulae and approximations of the geometries at high and low liquid contents. It is shown that the common assumption of liquid shells over ice spheres is both physically incorrect and leads to large errors.

ISSN:0021-8979    

DOI:10.1063/1.331186

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Counting neutron‐induced tracks in plastics as a function of the orientation relative to the arrival direction of incident neutrons makes possible a rugged method of measuring the direction, fluence, and average energy of a directional flux of fast neutrons and the distance and strength of the source.

ISSN:0021-8979    

DOI:10.1063/1.331187

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The collisional kinetics of upper state formation for the iodine monofluoride (IF) discharge pumped laser have been studied using tunable dye laser absorption spectroscopy. As for electron‐ beam excitation, the immediate precursor to IF*(D′) is found to be the I*(6s4P) species. Energy stored in the F*(4P) states, however, is not recovered in the laser’s output due to weak F*→I* collisional coupling. Limited tunability of this laser has been demonstrated with a Littrow prism and has resulted in the observation of a newD′→A′laser transition at 467 nm.

ISSN:0021-8979    

DOI:10.1063/1.331188

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A microwave method for determining the electron density in a high‐density plasma with or without a static magnetic field is presented. The method utilizes the cutoff frequency characteristic of a dielectric‐rod waveguide embedded in the plasma, the mode of propagation along the waveguide being such that it corresponds to the TMommode at cutoff. In certain cases the density can be calculated from simple formulae if the cutoff frequency is measured. The higher limit of the density that can be measured by usual microwave techniques can be increased considerably by using this method.

ISSN:0021-8979    

DOI:10.1063/1.331189

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The passivation of a bulk donor defect (Ec–0.36 eV) in polycrystalline GaAs by reaction with atomic hydrogen has been observed using deep level transient spectroscopy. The concentration profile of the defect is presented as a function of the duration and temperature of the exposure to atomic hydrogen—when exposed for 3 h at 250 °C, 3×1015donor defects cm−3were passivated to a depth of ∼1.1 &mgr;m.

ISSN:0021-8979    

DOI:10.1063/1.331190

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Shock temperatures of fused silica were determined using radiance intensity measurements at two color bands of 620 and 810 nm. The shock temperature increased from 2.0×103to 3.3×103K in the pressure range between 31.8 and 40.5 GPa, and up to 4.2×103K in the range up to 65.1 GPa. The rate of increase of temperature with pressure decreased at ∼40 GPa. The low gradient above 40 GPa suggests that a shock‐induced phase transformation of fused silica begins at ∼40 GPa.

ISSN:0021-8979    

DOI:10.1063/1.331191

出版商:AIP    

年代:1982

数据来源: AIP