Mechanical stress induced degradations of a MOS technology are investigated. Bidimensional stress simulations, coupled with electrical characterizations reveal the importance of the gate formation and TEOS deposition steps in the generation of mechanical stress. The use of a doped oxide as interlayer material between the polysilicon gate and the TEOS film is shown to significantly reduce the residual stress and associated electrical failures

The numerical modeling of the oxidation of silicon is analyzed from a nonlinear viscoelastic approach. Its mechanical and stress dependent parameters are determined for silicon dioxide and nitride. The study focuses on the rheological behavior of the materials. The two dimensional simulations of silicon cylinders oxidation and local oxidation of silicon processing reveal that at 1000 °C, a nonlinear viscous modeling is equivalent to the nonlinear viscoelastic one. But, for lower temperatures, the discrepancies between these two models, observed in the stress calculation and final oxide shape, demonstrate the necessity for a complete nonlinear viscoelastic formulation. Finally, the calibrated model is used to study the growth of a recessed isolation structure. The investigations quantify the influence of geometrical parameters of the silicon groove on the shape of the final isolation oxide (e.g., parameters such as the silicon overetch under the pad oxide, the depth of silicon etching, the slope of the silicon sidewall and the silicon concave corner rounding).

This paper describes the continuing development of the system SPII (here is the version 2) which is a simple backward chaining inference engine equipped with powerful fuzzy logic capabilities. Fundamentally, SPII-2 is able to accommodate both imprecision and uncertainty in the homogeneous framework of possibility theory. More specifically, in addition to evaluating the certainty of fixed hypotheses (which is about all what most present approximate reasoning systems can do) SPII-2 can take into account judgemental expertise about problems which require computation as well as reasoning on numerical quantities that may be pervaded by fuzziness. Beside presenting SPII-2 under various aspects (knowledge representation, techniques for approximate reasoning and computation, functioning issues), this paper discusses an application to an important petroleum geology problem that is the one of prospect appraisal.

SILSO wafers are analysed before and after different types of heat treatments. In the as-grown material, the electron diffusion length L is shown to vary from 20 to 90 μm, depending on the location in the different types of crystalline structure. The columnar structure behaves satisfactorily during heat treatments. On the contrary in the “transcrystalline structure” and in variable proportions, in the “transition structure” L drops down to small values, even with a strong getter effect. Consequently, in spite of the fact that the columnar structure itself allows conversion efficiencies of ≈10 %, large area solar cells (100 cm2) include too large regions of lower grade material and exhibit a conversion efficiency only slightly above 8 %.

Two Types of GaAlAs heterojunction electroluminescent diodes are compared. In the planar-type diffused diode the p-n homojunction is obtained by zinc diffusion in areas limited by a silicon nitride mask; the p-p heterojunction confines electrons in the bulk and avoids surface recombinations. The epitaxial diode is a conventional double heterojunction; the active area is limited by proton bombardment. The aging behaviors of these two types appear quite different. Diffused diodes degrade relatively fast; under continuous operation at 550 A/cm 2 (100 mA) the device lifetime (emitted light power falling down to 50 percent of the initial value) is 10 000 to 50 000 h. Epitaxial diodes degrade much more slowly; their device lifetime is estimated at several 10 5 h. The degradation is followed during aging, by using electrical and optical measurements, together with SEM and TEM analyses. It is confirmed that fast degradation occurs with simultaneous growth of dark line defects (DLD) and that these DLD's result from dislocation dipoles of interstitial nature, emitted either from scratches or, more frequently, from previously existing dislocations. It is shown that epitaxial diodes are practically free of dislocations; on the contrary, in the case of planar-type p-n junctions, a large number of dislocation loops are developed at the junction periphery, resulting from the mechanical stress at the edge of the junction during processing. This is the main source of DLD's and fast degradation of planar-type diffused diodes.

GaAlAs single heterojunctions are shown to be very efficient red light-emitting diodes (LED's). The high electron injection efficiency, high luminescence internal quantum efficiency (excellent material electronic quality), and low absorption lead to a high external quantum efficiency of electroluminescence (1 percent at 650 nm for uncoated devices). The absence of saturation of the brightness at high current densities allows the use of these GaAlAs LED's at high current pulses (for displays, screens) as well as at low CW current (low power consumption LED's).

This paper deals with the design, processing, and electrical characteristics of a new monolithic power device comprising a V.MOS Field-Effect-Transistor as the driver component, and a bipolar low Emitter Concentration Transistor as the power output component. The study of the device has been made on the base of a 3,9 × 3,9 mm2chip. The device design is such that there is a complete compatibility between processing of the multiepitaxial bipolar power transistor and of the V.MOS transistor. The influence of the main parameters of the structure was studied, including : - Channel width of the V.MOS - Gate oxide thickness - Characteristics of the epitaxial layers A diffusion processing insuring a high gain for the bipolar transistor and a low threshold voltage of the V.MOS F.E.T. has been developed. The electrical measurements exhibit nice characteristics for medium voltage applications: - low threshold voltage : Vth< 2,5 V - high forward transconductance : gm> 5 A/V - low saturation voltage drop : Vsat< 1.8 V (for Ic = 10 A, VG= 10 V) - medium breakdow-voltage : BV> 90 V.

2014 The need for light sources and detectors in optical communications has stimulated the evaluation of physical properties of the GaAs1-xSbx/Ga1-yAlyAs1-xSbx double heterojunction. In this paper the research is limited to the composition range 0 ~ x ~ 0.25, which corresponds to the spectral range 0.9-1.2 03BCm, specially attractive for optical fiber communications because of the lowest absorption and dispersion losses. In this research the metallurgical study is an important feature ; during the LPE growth, lattice matching has to be performed between the GaAs substrate and the ternary active layer. This is carried out by a particular step-greading technic where the compositional steps have to be progressively increased from the bottom to the top of the buffer layer. The results of the material characterization and of the measurements of properties of the double heterojunction devices thus performed are compatible and point out that the radiative transition efficiency decreases as the antimony content in the active layer is increased. This is ascribed to the degradation of the crystalline quality occurring when the lattice mismatch is too large to be solved by the step-grading buffer layer. So that the working range of GaAsSb is reduced to 0.9 to 1.1 03BCm where its electroluminescence performances are quite satisfactory and justify the interest of this compound. REVUE DE PHYSIQUE APPLIQUÉE TOME 13, DÉCEMBRE 1978, 1

The electroluminescence properties of GaAs, Gap and GaAsP diodes and displays are described. In each case, the nature of radiative recombinations, the interna1 and external quantum efficiency values, the limitations, the choie. criteria dealing with the device structure are precized. In conclusion, the expected improvements and the possibilities offered by more recently introduced materials such as GaInP, GaAlAs and GaN are presented.

Two types of applications need cross-bar structures, alphanumeric displays and panels. When the total number or the density of electroluminescent points is high it is necessary to use monolithic crystals, containing for example, 5 × 7 or 8 × 8 integrated points. Although others have proposed devices, using localized liquid-phase epitaxy of GaAs or of red GaP, this paper presents a new planar structure, similar to Si bipolar integrated circuits. It is based on either GaAsP or GaAlAs, which are direct band gap materials, non-transparent to their own radiation, and thus allow localization of the photon emitting areas.

Using the Schockley-Read-Hall statement of trapping and non-radiative recombination in semiconductors, a method of analysis of trapping centres is proposed, which is an extension of the one proposed by R. Williams. In a surface barrier diode made on GaAs, the imperfection levels of the material can be characterized by their concentration, energy depth and capture cross section. The results we have obtained allow the characterization of several levels. They are in good agreement with the conventional photoelectric analysis and give supplementary information.

We describe current oscillations in GaAs at 77 degrees K when electric field, applied in the [110] direction of the crystal, exceeds acritical value.