Distribution of the lifetime of consecutive k-within-m-out-of-n:F systems

The distribution of the lifetime (MTTF) of any consecutive k -within-m-out-of-n:F system, with independent exponentially distributed component lifetimes, is shown to be a convex combination of the distributions (MTTFs) of several convolutions of independent random variables, where each convolution represents a distinct path in the evolution of the system's history, and where in each convolution all but the last random variable is exponential. The last random variable in each convolution is either a zero lifetime or the lifetime of several disjoint consecutive k_i within m_i-out-of-n:F systems in series with each k_i<k, each m_i<m, and each n_i<n. This enables the calculations to proceed recursively. Calculations are facilitated by the symmetric nature of the convex combination     

200°C, 96-nm wavelength range, continuous-wave lasing fromunbonded GaAs MOVPE-grown vertical cavity surface-emitting lasers

We report record temperature and wavelength range attained using MOVPE-grown AlGaAs vertical cavity surface-emitting lasers (VCSEL's). Unbonded continuous-wave lasing is achieved at temperatures up to 200°C from these top-emitting VCSEL's and operation over a 96-nm wavelength regime near 850 nm is also achieved from the same nominal design. Temperature and wavelength insensitive operation is also demonstrated; threshold current is controlled to within a factor of 2 (2.5-5 mA) for a wavelength range exceeding 50 nm and to within ±30% (5-10 mA) for a temperature range of 190°C at 870 nm     

X-ray evidence for the absence of 90°-domains in polycrystalline PbTiO3 thin films with grains below a critical size

3 thin films is systematically studied by using X-ray diffraction (XRD). The PbTiO₃ thin films with different average grain sizes were prepared on various substrates by a sol-gel process. The films on NaCl and fused glass are randomly grain-oriented, while those on (111)Pt/Ti/SiO₂/Si are highly {100} cubic index grain-oriented . It is found from the XRD patterns of the films on NaCl that with decreasing average grain size from 230 to 80 nm, the intensities of high h index (h>l) peaks (hkl), such as (100), (110), (200), (201), (210), (211), etc., decrease rapidly and ultimately disappear, whereas another set of peaks (lkh), including (001), (002), (102), (112), etc., are still intense. This interesting result suggests that at grain size below a certain critical size an increasing number of grains no longer show 90°-domains, which is confirmed by TEM observations. Meanwhile, X-ray evidence of such a grain-size-related absence of 90°-domains is also found for PbTiO₃ films on Pt(111) and fused-glass substrates. The volume fractions of single-domain grains (without 90°-domains) in the films are estimated from their XRD patterns. By combining SEM and TEM investigations, the critical grain size for the formation of 90°-domains is further determined to be near 200 nm. Received: 19 December 1996/Accepted: 24 March 1997     

Inhomogeneities in silicon p-n-junctions

Latent macroscopic defects in silicon are detected by electrical and electron microscope measurements. They lead to anomalous temperature dependence of the Fermi level position and growth in the hole capture coefficient. A level with energy of 0.55 eV measured from the conduction zone controls the recombination process. It is proposed that macroscopic defects develop upon association of oxygen-silicon vacancy complexes. Action of an electron beam leads to reversible changes which increase upon multiple scanning, affecting the value of the diffusion length.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 71–75, April, 1991.     

Simple digital control improving dynamic performance of powerfactor preregulators

This paper presents the practical implementation of a fully digital control for boost power factor preregulators (PFPs). The control algorithm, which is simple and fast, provides a significant improvement in the system's dynamic performance compared to the usual analog control techniques. The paper discusses the design criteria and the actions taken for the implementation of the digital control, which is performed by means of a standard microcontroller (Siemens 80C166). The effectiveness of the approach is assessed by experimental tests     

An extraction method to determine interconnect parasitic parameters

Interconnect parasitic parameters in integrated circuits have significant impact on circuit speed. An accurate monitoring of these parameters can help to improve interconnect performance during process development, provide information for circuit design, or give useful reference for circuit failure analysis. Existing extraction methods either are destructive (such as SEM measurement) or can determine only partial parasitic parameters (such as large capacitor measurement). In this paper, we present a new method for extracting interconnect parasitic parameters, which can simultaneously determine the interlayer and intralayer capacitances, line resistance, and effective line width. The method is based on two test patterns of the same structure with different dimensions. The structure consumes less wafer area than existing methods. The method shows good agreement with SEM measurement of dielectric thickness in both nonglobal planarized and chemical-mechanical polished processes, and gives accurate prediction of the process spread of a ring oscillator speed over a wafer     

Monolithic rat-race mixers for millimeter waves

In this paper, we report on fully monolithic millimeter-wave Schottky-barrier diode (SBD) down-converters with an IF amplifier using heterojunction bipolar transistors (HBT's). A rat-race circuit is used for the mixer, and is analyzed using a harmonic-balance simulator. The measured conversion gain and the isolation are 7.1 and 29 dB in the V-band design, and 8.0 and 25 dB in the W-band design, respectively. The conversion gains are matched well with the circuit simulation     

Optical quenching of the magnetoplastic effect in NaCl crystals

Observations indicate that illuminating NaCl crystals by ultraviolet light (λ=350 nm) suppresses the magnetoplastic effect. The processes induced by illumination take place in a subsystem of point defects and are related to a change in the state of magnetically sensitive dislocation pinning sites. Fiz. Tverd. Tela (St. Petersburg) 39, 1389–1391 (1996)