Polysilicon Devices Research Articles

Analysis of minority-carrier transport in polysilicon devices

Key assumptions are made, with justification, to simplify the three-dimensional, nonlinear boundary-value problem that defines minority-carrier transport, including recombination, in polysilicon devices. These assumptions enable the separation of the grain-boundary recombination analysis, which is based on quasi-equilibrium in the space-charge region, from the intragrain transport analysis, which is done by partitioning the grain into subregions in which the minority-carrier flow is predominantly one-dimensional. The analyses are coupled through the effective minority-carrier recombination velocity at the grain boundary, which generally is dependent on the minority-carrier density in the quasi-neutral grain. Limitations of the model implied by the quasi-equilibrium assumption are effectively removed by recognizing that when conditions obtain that negate quasi-equilibrium, the effective recombination velocity is fixed at the minority-carrier kinetic-limit velocity. The model development is facilitated by computer-aided numerical analysis of the grain-boundary recombination and is supported by qualitative discussion of the underlying physics.

Electrical Properties of Composite Evaporated Silicide/Polysilicon Electrodes

MOS‐type capacitor structures were fabricated employing a composite polycrystalline silicon/refractory metal silicide electrode. Electrical characterization of oxidized structures has revealed that their behavior, compared with that of polysilicon devices, can remain unaltered by the addition of the conductive tungsten or molybdenum silicide film (other than an approximately 10–15× reduction in net resistivity of the electrode material). This compatibility, however, requires a minimum polysilicon thickness, or else an abnormally high incidence of shorting occurs following oxidation. The required thickness of the underlying polysilicon is larger than that required only to provide sufficient silicon for the oxidation process.

Breakover and negative resistance in polycrystalline silicon n-π-n DIAC's

The switching characteristics of polysilicon n-π-n devices present an extended negative-resistance region and allow large current densities. A breakover threshold field of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> V/cm has been deduced. It is suggested that polysilicon devices should be explored for switching applications.