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Impact ionization in semiconductors and hot-carrier injection in Si-MOSFETs

Thesis/Dissertation ·
OSTI ID:6336790

By incorporating non-parabolicity of energy band structure and energy-dependent impact ionization scattering rate into Keldysh's kinetic theory, an impact ionization model for electrons and holes in semiconductors is proposed. Numerically calculated impact ionization coefficients for Si, Ge, and GaAs in a wide range of electric fields and at different temperatures agree well with experimental data. The carrier energy distribution function numerically obtained from the model shows a distinct non-Maxwellian feature. The impact ionization model has been incorporated into a simulation model for substrate and gate currents in short n-channel Si-MOSFETs. Along with improvements in modeling of hot-carrier injection at the Si/SiO{sub 2} interface, the model successfully simulates and explains the experimentally observed second peak in the gate current versus gate voltage curve for very thin oxide devices and also the unusual behavior of the substrate and gate currents for lightly-doped-drain (LDD) devices which have not been simulated before. Based on the simulation results for LDD and related device structures, two new EPROM structures are proposed.

Research Organization:
Massachusetts Univ., Amherst, MA (USA)
OSTI ID:
6336790
Country of Publication:
United States
Language:
English