Hot carrier effects in depletion-mode MOSFETs

Abstract

Substrate current (I sub) due to the flow of hot holes from the drain depletion region of an n-channel depletion-mode transistor is measured. Three different types of transistors are fabricated by using various channel implantation doses with the same energy of implantation. A theoretical model is presented for I sub which agrees with the experimentally measured values. During gate current (I g) measurement, a change in polarity of the gate current due to channel hot carriers at a higher gate bias (V g) value is observed. At lower V g values the gate current is due to the flow of holes, and then electrons start flowing at higher V g values, which changes the I g polarity. It is observed that for high field effects the increase of drain bias has similar effects as a decrease of channel implantation dose required to fabricate the MOSFET.