Numerical analysis of amorphous and polycrystalline silicon semiconductor devices

• Generalization of the time-dependent analysis in presence of localized states. The transport model incorporates two more continuity equations for trapped electrons and holes; both free and trapped charges dynamics is thus described. The simulator has been used to study the current degradation in amorphous-silicon, inverted-staggered MOS devices, related to the slowest charge trapping processes in the device bulk. Performances of elementary circuits (NMOS and CMOS inverters) have also been studied.
• Generalization of the small-signal analysis. Two distinct recombination functions have been used in the small-signal continuity equations to take into account the exchange of charge between trap states and band states in response to an applied small-signal. The simulated C-V curves of gate-to-source and gate-to-drain capacitance of an amorphous-silicon MOS device agree well with measurements and show the influence of the trapped charge.
• Inclusion in the model of field-dependent generation phenomena, and in particular the band-to-band tunnel generation, the phonon-assisted trap-to-band tunnel generation and the Poole-Frankel generation. Simulations of polycrystalline thin-film devices showed good matching with measurements and allowed for a physical interpretation of the high leakage currents typical of these devices.

Researchers:

• L. Colalongo
• A. Pellegrini
• M. Valdinoci
• M. Rudan
• G. Baccarani

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