Summary and Outlook
The presented review of physical models for device simulators which rely on moments of the Boltzmann equation has shown a remarkable gap between the demands for highly accurate and efficient TCAD tools from the side of semiconductor industry and the availability of models that meet these requirements, partly caused by a lack of the fundamental physical understanding. This is somewhat surprising, because silicon has been the basic material of semiconductor research over more than three decades and is now the basic material of the second largest industrial branch. Among the deficiencies the following items are striking: A fundamental quantity like the intrinsic density of silicon is not precisely known. Heavily doped silicon is scarcely understood. This holds true for the bandgap energy, the mobility, and all recombination channels. Device models of bandgap narrowing disagree significantly in their quantitative predictions. There is no unique theory-based bulk mobility model which covers ultra-high doping concentrations and strong compensation. The actual recombination channel at high doping concentrations is not really known. Furthermore, local models of impact ionization or band-to-band tunneling have only a very limited value in modeling the strong nonlocal effects typical for sub-quarter-micron devices. Temperature-dependent models in EB or HD equations provide an approximate nonlocal description, but they also fail as soon as the high-energy tail of the distribution function becomes responsible for the physical effects.
KeywordsDevice Simulator High Doping Concentration Heavy Doping Strong Compensation Advance Physical Model
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