Avalanche Injection Effects in MIS Structures and Realization of N-Channel Enhancement Type MOS FETS

The avalanche injection of hot carriers in MIS structures, especially the significant charging effects observed in thermally grown SiO 2 films are studied in detail. The good controllability of the charging effects is found, and it is shown that the usual n-channel (depletion mode) MOS FETs can be easily converted to the enhancement type with the low threshold voltage. The equations of the avalanche injection current and the shift of flat band voltage are developed and appear to be good agreement with experiments. The electron traps which cause the negative charging effects are the water-related neutral centers, and their densities are in the order of 10 17 /cm 3 ( p -type 1 Ω-cm substrate). The interface states density increases and the properties of Si-bulk are also influenced by the avalanche injection.