Substrate current in short n-channel MOS transistors

Abstract

Abstract Tho substrain current against gate voltage characteristics or relatively short n-channel MOS transistors were examined for various substrate and drain voltages, channel length and surface doping conditions : namely without implantation, implantation for threshold voltage adjustment and implantation for depletion mode device types A, B and C, respectively. The substrate current may increase or decrease when increasing the aubstrate voltage magnitude duo to the fact that the drain current decreases and the multiplication factor increases with the substrate bias. The substrate current increases when decreasing the channel length. It increases for the devices of type B, but is lower for type C. These experimental results were qualitatively explained by using published models in which the substrate current is caused by low-level impact ionization within the pinched-off region. A simple model in which the ionization coefficient and the field derivative with respect to x wore assumed to be power-law fie...